Microbiology Case Study: A 24 Year Old Male with Painful Pustules

Case History and Laboratory Findings

A 24 year old male presented to an urgent care clinic with the complaint of painful pustules on his scrotum for the past 4-5 days. He claims that he had not had any recent exposure to sexually transmitted diseases (STD) or to new sexual partners. A month prior to presentation, he was seen for STD evaluation and was treated empirically for suspected exposure.  Testing at that time was negative.  The patient was unsure if these pustules were exacerbated by his work, in which he is in tight, hot spaces doing manual labor. His review of systems was otherwise negative. A swab of one of the pustules was sent for gram stain and culture which showed the following:

Image 1. Gram stain from a swab illustrating small intracellular Gram negative diplococci (100x, oil immersion).
Image 2. Chocolate agar showing small to medium, flat, grey-brown, and moist colonies.

MALDI-TOF identified the organism to be Neisseria gonorrhoeae.


N. gonorrhoeae is a gram negative diplococci and the second most common cause of sexually transmitted infections in the United States. The diplococci are described as having adjacent flattened sides giving it the appearance of the letter “D”. N. gonorrhoeae is classically described as a fastidious organism, requiring specialized media (Chocolate, modified Thayer-Martin, Martin-Lewis, New York City agar, etc.) and an enhanced CO2 environment in order to grow, though it is also known to grow on blood agar. Colonies are small to medium in size and are described as flat, grey-brown, and moist. Biochemically, N. gonorrhoeae is catalase and oxidase positive, and is a glucose fermenter.

Neisseria gonorrhoeae can infect the epithelium of the urethra, cervix, pharynx, rectum, and conjunctiva. Infection at these sites results in pain, irritation, and purulent discharge. Dissemination to other locations, such as the skin and joints, can also occur. Though dissemination is uncommon, associated symptoms include: skin sores, fever, migratory polyarthritis, tenosynovitis, and pauciarticular septic arthritis.  N. gonorrhoeae infections typically present as acute urethritis with associated discharge.  Infections are symptomatic in 10% of males and upwards of 70% of females, putting females at a higher risk of developing ascending infections, and potentially, pelvic inflammatory disease. Disseminated infections occur much less commonly, happening in 0.5% to 3% of all gonococcal infections. Therapy guidelines recommend treating uncomplicated infections with intramuscular ceftriaxone and oral azithromycin. Treatment of disseminated infections is variable depending on patient symptoms, but can include a combination of ceftriaxone/cefotaxime and azithromycin/doxycycline, with variable route of administration and length of treatment times. Susceptibility testing is limited to testing for beta-lactamase activity, though in cases of suspected resistance, CLSI guidelines are available for further testing.


  1. McCormack WM, Stumacher RJ, Johnson K, Donner A. Clinical spectrum of gonococcal infection in women. Lancet 1977; 1:1182.
  2. Workowski KA, Bolan GA, Centers for Disease Control and Prevention. Sexually transmitted diseases treatment guidelines, 2015. MMWR Recomm Rep 2015; 64:1.
  3. Centers for Disease Control and Prevention. Sexually Transmitted Disease Surveillance, 2015. Atlanta, GA: US Department of Health and Human Services; October 2016.


-Clayton LaValley, MD is a 2nd year anatomic and clinical pathology resident at the University of Vermont Medical Center.


-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Associate Professor at the University of Vermont.

Microbiology Case Study: A 56 Year Old Man with Bacteremia

Case History

A 56 year old man with a history of hypertension, asthma and COPD, bladder stones, congenital bladder abnormality, and bladder exstrophy presented to the ED with fatigue, generalized weakness, poor appetite, fever, and nausea. He had intermittent right flank pain and generalized abdominal pain. The patient also reported he had passed bladder stones in the past year.

In the ED he had an elevated peripheral white blood cell count of 12.9 x103/μl with a differential of 81% neutrophils, 11% lymphocytes, and 6% monocytes. His creatinine was elevated at 5.4 mg/dl. CT imaging of the urogenital tract showed hydronephrosis with evidence of infection.

Blood and urine specimens were sent for culture. The urine culture grew 10-50,000 cfu/ml Aerococcus urinae. After 30 hours of incubation, the anaerobic blood culture was positive for small, coccoid-looking gram positive rods (Image 1). The following bacteria grew on solid media under anaerobic conditions after 48 hours of incubation (Image 2).

Image 1. Gram stain showing small, coccoid-looking Gram-positive rods
Image 2. Tiny colonies growing on non-selective anaerobic media after 48 hours.


The organism growing in the blood culture was identified as Actinotignum schaalii. A. schaalii is a facultative aerobe that prefers enriched media and grows best in anaerobic or 5% CO2 environments. It is a non-hemolytic, non-motile, and non-spore forming Gram-positive rod. A. schaalii is negative for catalase, oxidase, CAMP factor, and nitrate reduction, but is hippurate positive. It is also negative for lactose, mannitol, raffinose, sorbitol, and trehalose acid production.

Actinotignum schaalii was formerly named Actinobaculum schaalii. The Actinotignum genus now consists of A. urinale, A. sanguinis, and A. schaalii. A. schaalii is part of urogenital microbiota in healthy adults and can cause urinary tract infections, especially as it thrives in the humid atmosphere of diapered children or elderly adults. Isolation of this organism is associated with urinary incontinence, bladder cancer, catherization, neurogenic bladder, renal failure, prostate cancer, and chronic renal failure. The presence of A. schaalii in the urogenital tract can progress to bacteremia and rarely it can also cause groin abscesses.

Actinotignum schaalii is an under recognized uropathogen due to its fastidious nature—it is slowly growing and prefers enriched media grown under anaerobic conditions. None of these conditions are met as part of a routine urine culture as urine cultures are often finaled in < 48 hours, they may not use enriched media, and they are incubated under aerobic rather than anaerobic conditions. Because of these factors, A. schaalii rarely grows in urine culture despite it being a known colonizer of the urogenital tract and occasional uropathogen. Instead it is most commonly recovered from blood cultures as a result of urosepsis. When colonies do grow from blood culture, they are very difficult to identify by biochemical methods. A. schaalii is often misidentified by biochemical panels as Arcanobacterium spp. or Gardnerella vaginalis (API Coryne system, bioMerieux), Actinomyces meyeri (Rapid ID32A system, bioMerieux), or Actinomyces israelii (Rapid ANA II system, Remel). In our lab Bruker Biotyper MALDI-TOF MS was able to identify A. schaalii with high confidence. Based on the most current literature, Vitek MS misidentifies A. schaalii as G. vaginalis or A. meyeri. This data is from 2015, so it’s possible the Vitek MS spectra database has been updated and now identifies A. schaalii.

A. schaalii is routinely susceptible to all β-lactams but requires an extended duration of antimicrobial treatment compared to other uropathogens. It is resistant to trimethoprim/sulfamethoxazole and quinolones, both of which are commonly prescribed for urinary tract infection. Therefore, patients with A. schaalii are at risk for recurrent urinary tract infections due to inappropriate or inadequate antibiotic treatment.

Our patient was prescribed ciprofloxacin for presumed urinary tract infection prior to his bacteremia. He was switched to ceftriaxone upon hospital admission. His bacteremia was cleared and the patient was discharged 5 days later on an oral β-lactam antibiotic. 


  1. Lotte, R., L. Lotte, and R. Ruimy. “Actinotignum schaalii (formerly Actinobaculum schaalii): a newly recognized pathogen—review of the literature.” Clinical Microbiology and Infection1 (2016): 28-36. Le
  2. Le Brun, Cécile, et al. “Urinary tract infection caused by Actinobaculum schaalii: a urosepsis pathogen that should not be underestimated.” JMM Case Reports2 (2015).
  3. Manual of Clinical Microbiology, 11th edition


-Erin McElvania, PhD, D(ABMM), is the Director of Clinical Microbiology NorthShore University Health System in Evanston, Illinois.

Microbiology Case Study: A 62 Year Old Male with Productive Cough

Case History

62 year old male from Louisiana with a medical history of COPD presents with fever, productive cough, weight loss, and a red nodule on the left hand. Chest x-ray shows interstitial and lobar infiltrates. Patient reports no recent travel history. Mycobacterial culture of the sputum is positive for an organism. MALDI-ToF of the sputum culture confirms the result.

Lab Identification

Image 1. Kinyoun stained long bacilli with a banded, ladder like pattern isolated from sputum culture.
Image 2. Bright lemon yellow colonies growing on LJ slant after exposure to light on the right compared with unpigmented control colonies on the left.
Image 3. Bright yellow colonies growing on 7H11 media after exposure to light on the right compared with unpigmented control colonies on the left.

Mycobacterium kansasii grows on 7H11 media and Lowenstein-Jensen (LJ) slants. The colonies appear smooth or rough and unpigmented when isolated in the dark. Upon exposure to light, colonies turn bright lemon yellow due to enhanced b-carotene production, which makes M. kansasii a photochromogen. M. kansasii stains positive with acid-fast stains. On Kinyoun stain, it shows long bacilli with a banded, ladder like pattern. M. kansasii is positive for nitrate reduction, catalase, urease, and tween hydrolysis. It is negative for niacin and pyrazinamindase. The identification of M. kansasii is confirmed by MALDI or DNA probe of an isolate.


Mycobacterium kansasii is a slow growing photochromogen, an organism that grows unpigmented colonies in the dark but produces a bright lemon yellow pigment upon exposed to light3. It is also an acid-fast positive long bacillus that causes TB-like chronic pneumonia, which is the second most common non-TB mycobacterial infection after MAC in the AIDS population. There are five genotypes of Mycobacterium kansasii. Genotypes I and II infect humans, with I being the most prevalent. Because environmental sources of M. kansasii are rarely identified, isolation of M. kansasii from a culture is never considered a contaminant.

M. kansasii is usually found in the tap water in cities endemic for the infection. In the U.S., it is most prevalent in the central and southern states including Louisiana, Illinois, Texas, and Florida1. Internationally, it is most prevalent in Israel, Korea, France, Japan, Portugal, with the highest incidence in England, Wales, and among South American gold miners.

The majority of patients with M. kansasii infection have an underlying pulmonary disease such as COPD, bronchiectasis, or TB infection3. The clinical manifestation of M. kansasii infection includes a primarily unilateral cavitary infiltrate in the lungs without pleural effusions. Patients are generally older compared with those infected with TB. They present with productive cough, weight loss, fever, night sweats, and dyspnea. Symptoms are usually less severe but more chronic compared with those of TB pneumonia. M. kansasii can also present as cutaneous lesions similar to sporothrichosis. Lesions include nodules, pustules, red plaques, and ulcers1.

M. kansasii infection is diagnosed by chest X-ray or chest CT, positive respiratory culture, and clinical exclusion of other diagnoses2. The criteria for a positive culture include either two consecutive positive sputum cultures, one positive culture from bronchoscopy specimens, or one positive culture with compatible clinical symptoms2. The treatment of M. kansasii infection depends on the resistance of the organism to rifampin. Rifampin-sensitive organisms are treated with at least three drugs including rifampin, ethambutol, isoniazid, and pyridoxine1. Rifampin-resistant organisms are treated with three drugs including clarithromycin or azithromycin, moxifloxacin, ethambutol, sulfamethoxazole, or streptomycin1. Due to drug interaction, rifampin is contra-indicated among HIV patients taking protease inhibitors and nonnucleoside reverse transcriptase inhibitors. Because rifampin increases the metabolism of these HIV medications, it can lead to HIV drug resistance among these patients.



  1. Akram SM, Bhimji SS. Mycobacterium Kansasii. StatPearls. 2018. https://www.ncbi.nlm.nih.gov/books/NBK430906/
  2. Johnston JC, Chiang L, Elwood K. Mycobacterium Microbiol Spectrum. 2017;5(1):TNMI7-0011-2016. doi:10.1128/microbiolspec.TNMI7-0011-2016.
  3. Meraz A, Raheem S. Pulmonary Mycobacterium Kansasii Infection –A Tale of a Right Upper Lobe Cavitary Lesion [abstract]. Journal of Hospital Medicine. 2015; 10 (suppl 2). https://www.shmabstracts.com/abstract/pulmonary-mycobacterium-kansasii-infection-a-tale-of-a-right-upper-lobe-cavitary-lesion/. Accessed March 12, 2018.


-Ting Chen, MD is a 1st year anatomic and clinical pathology resident at the University of Vermont Medical Center.


-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Associate Professor at the University of Vermont.

Microbiology Case Study: A 50 Year Old Man with Altered Mental Status

Case Histor

A 50 year old man presented to the emergency room with altered mental status, fever, and hypotension. His medical history was significant for quadriplegia, chronic indwelling urinary catheter with frequent urinary tract infections, and diabetes mellitus. The patient was intubated and started on vasopressors for presumed septic shock. CT scan of the abdomen showed dilated loops of bowel with possible ileus and pneumoperitoneum around the sigmoid colon.

Laboratory Identification

  • Clostridium difficile Fecal PCR: Negative
  • Fecal Bacterial Pathogen PCR: Negative for Salmonella spp., Shigella or Enteroinvasive E. coli spp., Campylobacter spp., or Shiga toxin producing genes
  • Urine culture: 2 strains of Pseudomonas aeruginosa and Klebsiella pneumoniae

Blood culture: At 41 hours, two of four blood culture bottles became positive (one aerobic bottle in each set). Gram stain showed budding yeast with pseudohyphae (Image 1). Growth of white, smooth colonies with foot-like projections was observed on agar (Image 2). MALDI-TOF analysis confirmed identification of the organism as Candida albicans.

Image 1: Gram stain of blood culture bottle demonstrating yeast form (left) and pseudohyphae (right).
Image 2: Colony morphology on chocolate agar demonstrating smooth white colonies with surrounding “feet.”


Candida spp. are the most common yeast cultured from clinical specimens. Candida albicans is characterized macroscopically by growth of smooth, white colonies with surrounding “feet” which represent projections of pseudohyphae. The pseudohyphae are distinguished microscopically from true hyphae by constriction of the cells where they meet (with true hyphae, the cell walls will remain parallel). When incubated at 37 C for 2 hours C. albicans will produce germ tubes (extensions from the yeast cell representing an attempt at forming true hyphae).

Candida spp. are normal flora found in the gastrointestinal tract, mucous membranes, and skin. Invasive candidiasis is typically an opportunistic infection with the patient’s own, endogenous flora (although nosocomial spread also occurs). Although it can be normal skin flora, the growth of Candida spp. from a blood culture should be presumed to be pathogenic; treatment should be initiated, and attempts made to identify the source. Typically, invasive candidiasis arises from one of three sources: 1) colonization and biofilm formation on an indwelling intravenous catheter 2) dissemination from a deep nidus of infection (often urinary tract) or 3) translocation from the gastrointestinal tract. Patients in intensive care, those who are immunocompromised, at extremes of age, those who have been on broad spectrum antibiotics, and those with GI tract perforation or anastamotic leaks post-operatively are at greatest risk for developing invasive candidiasis.

C. albicans has historically been the most common species of yeast causing invasive disease. However, non-albicans species (C. glabrata, C. parapsilosis, C. tropicalis and C. krusei) now cause almost 50% of invasive candidiasis. This changing epidemiology is relevant because the different species demonstrate different susceptibility profiles to antifungal agents, including azoles and echinocandins. C. auris is another recently emerging species that shows resistance to multiple antifungal agents, and has been described as causing outbreaks of healthcare-associated infections.

Although the patient’s chronic indwelling urinary catheter raised suspicion for a urinary source of the candidemia, the urine culture failed to support that theory. Given the findings of the CT abdomen in this patient, translocation from the GI tract is favored as the source of the candidemia. The patient’s history of treatment with antibiotics for repeated urinary tract infections, however, may have placed him at greater risk for developing invasive candidiasis.

-Alison Krywanczyk, MD is a 4th year anatomic and clinical pathology resident at the University of Vermont Medical Center.


-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Associate Professor at the University of Vermont.


Hematopathology Case Study: An 85 Year Old Man with Pancytopenia

Case History

An 85 year old man presented with pancytopenia and weakness. His labs include WBC of 3.2, HgB of 9.9 and platelets of 137.

Bone Marrow Biopsy

Bone Marrow Aspirate, 10x
Bone Marrow Aspirate, 40x
Core Biopsy, 10x
Core Biopsy, 40x

Flow Cytometry





The bone marrow aspirate shows multiple cellular spicules with a prominent population of lymphoid cells with oval to reniform nuclei, dispersed chromatin and abundant pale cytoplasm. Scattered plasma cells are also present.

The core biopsy shows an infiltrating population of atypical lymphocytes with moderate amounts of pale eosinophilic cytoplasm and mature chromatin that stain positive for CD20. Frequent mononuclear cells consistent with plasma cells are also seen scattered throughout the bone marrow and stain positive for CD138.

Flow cytometry revealed that 80% of the lymphoid gate represented a kappa light chain restricted population that co-expressed B-cell markers CD19, CD20 and CD22 along with classic hairy cell leukemia specific markers CD11c, CD25 and CD103. A second population of kappa restricted cells fell in the plasma cell gate. The cells co-expressed CD138, CD56 and were largely negative for CD19 and CD20.

Overall, there is a hypercellular bone marrow with a prominent mononuclear lymphoid infiltrate consistent with hairy cell leukemia and a concurrent population of plasma cells consistent with plasma cell neoplasm.


Hairy cell leukemia is a rare lymphoid neoplasm that accounts for only 2% of lymphoid leukemias. Patients tend to be in their 50s-60s with a 4:1 male predominance. The tumor is generally found in the bone marrow and spleen with rare circulating cells in the peripheral blood. Patients are generally cytopenic at presentation and symptoms include weakness and fatigue. Splenomegaly is common and hepatomegaly can also be seen.. 1

Hairy cell leukemia involves the clonal expansion of B-cells with a unique immunophenotypic profile. They are bright for CD19, CD20, CD22 and CD200, negative or dim for CD5, CD23 and CD10 and positive for CD11c, CD103, CD123 and CD25. Hairy cell leukemia must be distinguished from two provisional entities, hairy cell leukemia-variant and splenic diffuse red pulp lymphoma. These two entities do not have the classic morphology or staining profile of hairy cell leukemia.2

BRAF V600E mutations are detected in more than 80% of cases of classic hairy cell leukemia. The mutation is considered to be a driver mutation, but additional mutations are usually present that lead to disease progression. Hairy cell leukemia-variant is usually negative for BRAF mutations and has a more aggressive clinical course.3

Patients with hairy cell leukemia are given purine analogues as first line treatment and generally do well. However, patients who do not respond or who undergo relapse have few options. Increasingly, BRAF V600E inhibitors are being used for patients with hairy cell leukemia. Multiple studies have now confirmed the efficacy of vemurafenib and dabrafenib, however patients can be quick to relapse once off the drugs. Combination approaches should be considered for the most effective treatment. 4


  1. Swerdlow SH, Campo E, Harris NL, et al. WHO Classification of Tumours of Haematopoetic and Lymphoid Tissues (Revised 4th edition). IARC: Lyon 2017.
  2. Troussard X, Cornet E. Hairy cell leukemia 2018: Update on diagnosis, risk‐stratification, and treatment. American Journal of Hematology. 2017;92(12):1382-1390. doi:10.1002/ajh.24936.
  3. Maitre E, Bertrand P, Maingonnat C, et al. New generation sequencing of targeted genes in the classical and the variant form of hairy cell leukemia highlights mutations in epigenetic regulation genes. Oncotarget. 2018;9(48):28866-28876. doi:10.18632/oncotarget.25601.
  4. Roider T, Falini B, Dietrich S. Recent advances in understanding and managing hairy cell leukemia. F1000Research. 2018;7:F1000 Faculty Rev-509. doi:10.12688/f1000research.13265.1.


Marcus, Chelsea_099-Edit

Chelsea Marcus, MD is a third year resident in anatomic and clinical pathology at Beth Israel Deaconess Medical Center in Boston, MA and will be starting her fellowship in Hematopathology at BIDMC in July. She has a particular interest in High-grade B-Cell lymphomas and the genetic alterations of these lymphomas.

Microbiology Case Study: A 49 Year Old with HIV and CNS Lymphoma

Case History 

A 49 year old African American female was transferred from an outside hospital due to orbital cellulitis. Her past medical history was significant for HIV, CNS lymphoma, for which she was taking methotrexate & rituximab, and type II diabetes. Her vitals were: blood pressure 181/145, heart rate 145, temperature 98.6°F and respiratory rate 20. On physical examination, her right eye was bulging, with conjunctiva & eyelid swelling, and her iris was non-reactive. Scant serous drainage was noted. Admission labs showed a normal white blood cell count (9.8 TH/cm2), glucose of 211 mg/dL (normal: 74-106 mg/dL), hemoglobin A1C of 7.7% (normal: 4.2-6.0%) and platelets were low at 41,000 TH/cm2. An infection was suspected and the patient was started on vancomycin and piperacillin-tazobactam. She had a head CT scan which showed right periorbital cellulitis and diffuse sinus disease but no abscess formation. Nasal endoscopy was performed and extensive adhesions & black colored, necrotic tissue of the right nasal cavity was noted in addition to whitish debris, consistent with fungal overgrowth extending into the nasopharynx. Biopsies were taken for frozen section and bacterial & fungal culture and Infectious Disease was consulted for management of a probable rhinocerebral fungal infection.

Laboratory Identification

Image 1. Biopsy of the right nasal wall showed tissue invasion and necrosis with broad, ribbon like hyphae that were pauciseptate and branched at right angles (H&E, 40x).
Image 2. Fluffy, white fungal growth on Sabouraud Dextrose and Sabouraud Dextrose with Chloramphenicol agars at 72 hours of incubation at 25°C. There was no growth on the Mycobiotic agar slant.
Image 3. Tape prep showed a round sporangium containing small sporgangiospores located directly below the rhizoids of the mold which is consistent with the diagnosis of Rhizopus spp. (lactophenol cotton blue, 40x).


Rhizopus spp. belong to the order Mucorales, are ubiquitous in the environment and are the most common etiologic agents of mucormycosis. Rhizopus spp. typically cause invasive infections in the nasal sinus, brain, eye and lung, particularly in patients that have uncontrolled diabetes, HIV or are immunosuppressed. Mucorales are angioinvasive, exhibit perineural invasion and there is usually thrombosis, infraction and necrosis of surrounding tissue. As the illness can progress quite rapidly, prompt diagnosis and treatment is necessary.

If a Mucorales is suspected, tissue specimens obtained during a surgical procedure should be sent for frozen section, direct examination with calcofluor white/KOH and fungal culture. On histologic exam or microscopic exam in the microbiology laboratory, the hyphae of Rhizopus spp. are wide & ribbion-like with few to no septations (pauci- or aseptate) and wide angle branching (90°) (Image 1). Further classification requires culture.

If a Mucorales is suspected, the tissue submitted for fungal culture should be minced into small pieces and directly applied to the appropriate fungal media. Grinding of tissue will kill the hyphae and result in no growth from culture. Mucorales will not grow on media containing cycloheximide. Rhizopus spp. grow rapidly within 1-4 days and start as white, fluffy colonies that become grey or brown in color as they mature (Image 2). The Mucorales are described as “lid lifters” due to their rapid growth and “cotton candy” like colonies that fill the plate. On lactophenol cotton blue prep, Rhizopus spp. have unbranching sporangiophores that terminate in a round sporangium and arise directly under well-developed rhizoids (Image 3). The sporangium ruptures when mature and releases many oval sporangiospores.

Treatment of patients with mucormycosis is usually a dual approach with wide surgical excision and amphotericin B, which has been shown to be an effective anti-fungal drug in the majority of Mucorales. In contrast, voriconazole has poor activity against these isolates. If susceptibility testing is needed, CLSI provides reference broth microdilution guidelines. In the case of our patient, due to the grave prognosis of her condition, in addition to her other comorbidities, the family elected for comfort care measures only and board spectrum anti-fungals were not started.



-Lisa Stempak, MD, is an Assistant Professor of Pathology at the University of Mississippi Medical Center in Jackson, MS. She is certified by the American Board of Pathology in Anatomic and Clinical Pathology as well as Medical Microbiology. She is the Director of Clinical Pathology as well as the Microbiology and Serology Laboratories.  Her interests include infectious disease histology, process and quality improvement and resident education.

Beyond the CBC and Reticulocyte Count: Early Detection of Iron Deficiency Anemia

In my May 2018 post (Not your Grandmother’s Hematology), I discussed the history of hematology and chronicled how far we have come in the last 60 years. We have progressed from manual counting of cells to the first Coulter Counter in 1956, which revolutionized hematology by being able to automate the counting of red blood cells, to modern instruments that can report up to 30 parameters and perform up to 400 CBCs an hour. Among these parameters are what are termed advanced clinical parameters, new parameters which provide physicians with additional information about the state of blood cells. In this blog I will explore how one of these advanced clinical parameters, the Reticulocyte Hemoglobin content, can provide physicians with information that can assist them with earlier detection, differential diagnosis and better management of iron deficiency and iron deficiency anemia. 

Case Study 

A 29 year old female was seen by her gynecologist reporting a history of heavy menstrual bleeding with current bleeding lasting 15 days. The doctor discussed various treatment options with the patient and a CBC was performed. CBC results are shown below.

Test Result Flags Reference
WBC 7.23   4.5-10.5 K/CMM
RBC 4.38   3.70-5.30 M/CMM
HGB 12.0   12.0-15.5 GM/DL
HCT 36.2   36.0-46.0 %
MCV 82.6   80-100 FL
MCH 27.4   27.0-34.0 PG
MCHC 33.1   32.0-36.0 %
PLT 243   150-450 K/CMM
MPV 11.0   9.6-12.0 FL
RDW 12.5   0-15.1 %

This CBC shows no abnormal flags. Based on patient history and presentation, the physician questioned iron deficiency despite normal hemoglobin and hematocrit, MCV and MCHC. He ordered a reticulocyte profile on the same specimen with the following results:

Test Result Flags Reference Range
Retic 1.55   0.5-2.0 %
Abs Retic 0.0679 H 0.0391-0.057 M/CMM
Imm Retic Frac 14.9   2.3-15.9 %
Ret-Hgb 24.6 L 30-35 PG

Reticulocyte counts are the quantity of the youngest red blood cells released from the bone marrow into the peripheral blood. Reticulocytes are reported as a % and the absolute reticulocyte count is calculated by multiplying the Retic% by the RBC. The immature reticulocyte fraction (IRF) is the rate of production of reticulocytes and depends largely on the ability of the bone marrow to respond to erythropoietin. The reticulocyte hemoglobin (Ret-He) content is the amount of hemoglobin in newly formed red blood cells. (There are two different hematology systems that report reticulocyte hemoglobin content. The two nomenclatures used for reticulocyte hemoglobin are Ret-He and CHr and studies have been done that demonstrate their equivalence)

Note that the Ret-He reflects the quality of the newly formed reticulocytes. Ret-He is a direct measurement of the amount of hemoglobin in each reticulocyte, which indicates the amount of iron available for incorporation into the precursors of mature red cells. This patient’s retic% and IRF are within normal ranges, but her absolute reticulocyte count is high. A Ret-He less than 29 pg in an adult is indicative of iron deficiency. With a normal CBC and low Ret-He, this is an early indication that iron deficiency is indeed present. With the absence of sufficient iron, this patient would eventually develop a microcytic, hypochromic anemia. Therefore, Ret-He can measure and indicate inadequate hemoglobin production before the hemoglobin and hematocrit decrease.

In this case the importance of clinical awareness is illustrated. This physician remembered a recent laboratory technical bulletin announcing implementation of a new hematology analyzer system with the availability of new parameters for reticulocyte counts. When the CBC results came back from the laboratory, the patient had already gone home, and no serum had been drawn to perform a ferritin level. Rather than calling the patient back to have another sample drawn, the Ret-He could be done from the same blood sample already in the lab. Ret-He is a faster, easier and less expensive test than additional iron studies and bone marrow iron stains. Ret-He can easily be used at a very low cost to get that first piece of information to decide whether or not iron deficiency is a concern. A high or normal Ret-He would have ruled out an iron deficiency with a fairly high confidence level. In this case, the low Ret-He could be used to guide further workups. A subsequent blood drawn revealed a low ferritin and iron deficiency was confirmed. The patient was advised to take an iron supplement along with ongoing treatment for the bleeding.

This case is just one example of the clinical utility of the Ret-He. Using the Ret-He, physicians can determine iron deficiency before iron deficiency IDA develops. A low Ret-He can alert a physician to iron deficiency without the presence of anemia, microcytosis or hypochromia. Ret-He can also be used to monitor and show early response to iron therapy before any other parameters change. A case example is that of a 5 month old who was brought to the emergency room with a Hgb of 7 g/dl and a Ret-He of 11.9 pg. In pediatric patients, a Ret-He less than 27.5 is an indicator of IDA. In this child, treatment with oral iron showed that the Ret-He had risen to 24.6 pg seven days after the onset of iron therapy, while the CBC remained virtually the same. This provided a very early indication that the iron therapy was effective.1 The Ret-He can also been used to minimize transfusions. The AABB Choosing Wisely Campaign lists 5 things that physicians and patients should questions before transfusion. One of the guidelines states “Don’t transfuse red blood cells for iron deficiency without hemodynamic instability.“2 Historically, physicians have used a ‘wait and see’ approach and watched Hgb levels drop before they start looking at iron. Using a Ret-He, iron deficiency could be determined, for example, in a patient with a Hgb of 11 g/dl. Oral or intravenous iron could be started before the Hgb drops below 7 g/dl and transfusion becomes necessary. The AABB Choosing Wisely Campaign emphasizes this by stating that patients with chronic iron deficiency or pre-operative patients with iron deficiency should be given iron therapy before transfusion is considered.2 Ret-He can give the earliest indication of iron deficiency and can be used to monitor the response to iron therapy. Another clinical utility of Ret-He has been to help diagnose or rule out iron deficiency in oncology patients. Additionally, Ret-He has been included in guidelines for anemia management in end stage renal disease patients on dialysis and who get erythropoietin.

The Ret-He parameter has proved clinically useful in early determination of functional iron deficiency. Traditionally ordered chemistry iron studies are indirect measures that have certain inherent inaccuracies due to the presence of inflammation and infection, or in patients on iron therapy. Ret-He is a direct and very effective screening tool and physicians can use Ret-He with other RBC indicies to improve anemia diagnosis and management in many patient populations. Ret-He can be used as a screening measure, and used to reflex for iron studies. Therefore, laboratories who have instruments that can report Ret-He and CHr should develop an education program to help clinicians effectively use Ret-He. Together physicians and laboratorians can develop their own guidelines for reflex testing and improvement for patient care.


  1. Case Studies Demonstrating the Clinical Application of the Advanced Clinical Parameters (1/20/2016) Chantale Pambrun, MD, FRCPC, Head of Division of Hematopathology and Assistant Professor of Pathology and Laboratory Medicine, IWK Children’s & Women’s Health Centre and Dalhousie University
  2. https://www.aabb.org/pbm/Documents/Choosing-Wisely-Five-Things-Physicians-and-Patients-Should-Question.PDF
  3. Advanced parameters offer faster, surer guidance to cancer care. Anne Paxton. CAP Today. Sept 2017
  4. The Value-driven Laboratory. Reticulocyte Hemoglobin Content (Ret-He): A Parameter Well-Established Clinical Value. Sysmex America White Paper.
  5. Sysmex Clinical Support Team. Utility of RET-He, August 10. 2015
  6. Brugnara C, Schiller B, Moran J. Reticulocyte hemoglobin equivalent (Ret-He) and assessment of iron-deficient states. Clinical Laboratory Hematology 2006;28:303 – 308.



-Becky Socha, MS, MLS(ASCP)CM BB CM graduated from Merrimack College in N. Andover, Massachusetts with a BS in Medical Technology and completed her MS in Clinical Laboratory Sciences at the University of Massachusetts, Lowell. She has worked as a Medical Technologist for over 30 years. She’s worked in all areas of the clinical laboratory, but has a special interest in Hematology and Blood Banking. When she’s not busy being a mad scientist, she can be found outside riding her bicycle.