Procalcitonin: Sepsis Marker Extraordinaire?

Sepsis is one of the most common causes of significant morbidity and mortality in hospitalized patients as well as the most common cause of death in ICU patients.  In addition, the earlier sepsis is identified and treated, the better the prognosis for the patient. We actually do not have a biochemical marker which can be used to effectively diagnose sepsis. Sepsis diagnosis depends on finding microbial infection by culture, and while PCR methods do exist to quickly identify bacteremia, in most institutions cultures take at least 24 hours to grow.  To aid in the diagnosis, clinicians can check three biomarkers commonly considered “sepsis” markers: C-reactive protein (CRP), erythrocyte sedimentation rate (ESR) and procalcitonin (PCT).

Despite being very different tests, these three assays are ultimately indicators of inflammation or the inflammatory response. ESR is a simple manual test that measures how far red cells sediment out of a blood sample in one hour. It is used as a marker of inflammation but is quite unspecific; several conditions can cause inflammation. The ESR can tell a clinician that inflammation exists but not the cause of that inflammation CRP is an acute phase reactant protein. Its production by the liver increases in acute inflammation. However, its levels will be affected by liver dysfunction. PCT is a pro-hormone produced by extra-thyroidal immune cells within 2-4 hours of a bacterial insult or an inflammatory response.

Deciding whether a biomarker is a good indicator of sepsis is made difficult by its complex pathology. Studies that show one marker performs better are contradicted by other studies that show it does not. The utility of PCT for predicting sepsis remains controversial for this reason. However PCT has shown to be useful for predicting prognosis in sepsis. Increasing PCT concentrations correlate with increasing severity and a poor prognosis. Decreasing or low concentrations indicate a good prognosis. PCT is also being used to guide antibiotic therapy, although this use should be limited to non-surgical/trauma ICU patients, which is where the studies have been done. Thus although PCT proponents consider it to be the best available biomarker indicator of sepsis, none of the three tests have been shown to be good at diagnosing sepsis. Unfortunately, all three of these biomarkers are indicative of an inflammatory response and not specific for sepsis itself. However, once sepsis is known, all three biomarkers can be used to monitor its progression and response to therapy.

If you’d like to read more about PCT and sepsis, you can do so here:

http://www.nlm.nih.gov/medlineplus/ency/article/000666.htm

http://www.webmd.com/a-to-z-guides/sepsis-septicemia-blood-infection

http://www.medscape.com/viewarticle/720621_1

https://www.aacc.org/members/nacb/NACBBlog/lists/posts/post.aspx?ID=16#

 

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-Patti Jones PhD, DABCC, FACB, is the Clinical Director of the Chemistry and Metabolic Disease Laboratories at Children’s Medical Center in Dallas, TX and a Professor of Pathology at University of Texas Southwestern Medical Center in Dallas.

Dangerous Beauty

Potentially deadly pathogens have never looked so good. A false-color electron-microscope slideshow on Discover depicts organisms such as Campylobacter and Streptococcus pyogenes in a whole new light. Apparently actresses and models aren’t the only ones who benefit from Photoshop.

 

Swails

Kelly Swails, MT(ASCP), is a laboratory professional, recovering microbiologist, and web editor for Lab Medicine.

Are Antibacterial Soaps Effective?

The FDA is asking manufacturers to prove the effectiveness of their antibacterial products that use triclosan or triclocarban as the active ingredient. (See the press release here.) This comes on the heels of last week’s announcement of their plan to help phase out the use of medically important antibiotics in food animals.

When I became a microbiologist I stopped using products with triclosan in an effort to curb antibiotic resistance. While I like to see the FDA’s efforts, I wonder if they’re doing too little, too late, and I’m not the only one.

Some additional reading on the topic:

1. Mechanism of triclosan resistance study, published 1999.

2. Another triclosan resistance study, published 2006.

Edited to add: Maryn McKenna’s excellent write-up on the topic.

Swails

-Kelly Swails is a laboratory professional, recovering microbiologist, and web editor for Lab Medicine.

‘Tis the Season

The holiday season is rife with celebrations. Tree Trimmings! Presents! Gatherings! And let’s not forget the food. Turkey! Dressing (with or without oysters)! Cookies and its glorious dough! An unfortunate side effect of holiday celebrations is food poisoning, specifically those caused by, Salmonella, Campylobacter, and Vibrio.

According to the CDC, Salmonella and Campylobacter are in the top five pathogens with Salmonella being the biggest culprit in hospitalization. If you want to prevent Salmonella poisoning—or think you might already have it—here’s a handy guide to causes, symptoms, and treatment.

Raw eggs and mishandled poultry aren’t the only causes of food poisoning, though. Shellfish can be a concern, as is undercooked beef and unpasteurized dairy products. The Mayo Clinic has a wonderful chart describing the major food poisoning pathogens. A noticeable omission is Bacillus cereus, which breeds quite nicely in leftover rice.

For laboratory professionals, foodborne illnesses are a common cause of laboratory-acquired hospital infections. Be vigilant when handling enteric specimens and enteric cultures. Observe basic lab safety—use personal protective equipment, don’t use personal electronics in the lab, and be obsessive about washing your hands. Don’t let Salmonella or one of his buddies ruin your holiday season.

 

Swails

Kelly Swails, MT(ASCP), is a laboratory professional, recovering microbiologist, and web editor for Lab Medicine.

Dirty Winds

Over at Body Horrors, Rebecca Kreston writes about public health concerns of infectious disease and parasites. In this thought-provoking post, she discussions musicians (specifically, those who play wind instruments) and lung infections. She cites several small studies that found pathogens (Mycobacterium, Stenotrophomonas, and Cryptococcus) in instruments such as saxophones and trumpets.

The moral of the story: horn musicians, clean your instruments. And don’t ignore a persistent cough.

Swails

Kelly Swails, MT(ASCP), is a laboratory professional, recovering microbiologist, and web editor for Lab Medicine.

The Post-Antibiotic Era, Part 2

Linking to a few articles by Maryn McKenna because you need to read them.

In this blog post, Ms. McKenna writes about a man from New Zealand who died from a bacteria completely resistant to all antibiotics.

In this article, she imagines the post-antibiotic world. In a nutshell: it’s a scary place.

-Kelly Swails

 

 

A Possible Method to Diagnose Invasive Meningococcal Infection

Saying the word “meningitis” is a sure-fire way to scare parents of young children or college students. Invasive infections caused by Neisseria meningitidis are rare but serious. Mortality rates can run around 15%; complications include amputations due to tissue necrosis and hearing loss. In short, N. meningitidis infections are nothing to mess around with.

In order to avoid death and extremity loss, the infection needs to be diagnosed early. Trouble is, the early symptoms can be similar to those of a run-of-the-mill viral infection. Some patients do not exhibit the elevated white blood cell count so common in bacterial infections. Without clear signposts to guide the way, how can clinicians catch this fast-moving infection early in its course? A handful of esoteric hematology parameters might hold the key.

Demissie et al recently published this paper in The Pediatric Infectious Disease Journal about using neutrophil counts to diagnose meningococcal infection in children. It’s behind a paywall, but here’s the gist:

-Your automated hematology analyzer needs to report immature white blood cells.

-Using total white blood cell (WBC) counts or total neutrophil counts alone is insufficient.

-The parameters to check are absolute neutrophil count (ANC), immature neutrophil count (INC), and immature-to-total neutrophil ratio (ITR).

-Patients with invasive meningococcal infection (or, the authors also say, a serious bacterial infection) display abnormalities in at least one of the three parameters.

What do you think about these guidelines? Do you think they’d be effective in diagnosing invasive meningococcal infections?

-Kelly Swails