You Should Follow Troponins, Or They’ll Follow You

Hi everyone! Back with another piece about the life between the lab and medical school. This time, I’d like to take a minute to talk about some new and exciting developments in laboratory diagnostics happening right now: immunoassays for critical troponins are undergoing an evolution. Fourth generation testing is slowly developing into its fifth-generation upgrade. Labs across the country are starting to discuss the relatively new FDA approved fifth-gen cardiac troponin T assay which has been shown to be a high-sensitivity test. But what does this mean for labs? Specifically, what does it mean between the bench and the bedside? The hospital I’m currently on service at is rolling out the first beta-test of this assay in New York City right now, and as it turns out—it’s going to change a lot. Not only will the new understanding of cardiac enzyme reference ranges need a complete overhaul but tailoring appropriate clinical responses to those values will need to be looked at as well. I’m not a sales rep and this isn’t going to be an adventure in comparative statistical analytics, but I think it’s a great time to have a conversation early on about what these new generation assays could mean for us in the lab.

A Whole New World

When I was in graduate school, doing my MLS training we were taught the same cardiac enzyme assay history that was developed over the last 50 or so years. Early acute markers of inflammation relating to acute myocardial infarctions (AMIs) with respect to acute phase reactants AST, LDH, CRP, etc. As more technology advanced, specific biomarker analyses of individual detection of things like CK or myoglobin became useful. The WHO criteria for AMI then established (and re-established since the 1970s) the laboratory requirements for CK-MB and detectable levels of troponin to correlate with clinical findings. Further sensitivity and specificity developments, and clinical research like the GUSTO and APACE trials, showed us just how sensitive newer (then troponin T and I) cardiac assays could be. Not to mention, instead of rule-in/rule-out criteria, we had the development of risk stratification. And as instrumentation developed so did our testing—CK and LDH replaced with CK-MB and its isoforms, AST went the way of Myoglobin, and LD ratios became reliable troponins!

troponin-tab-1
Table 1. In each stage of acute coronary syndrome (ACS) various biomarkers are available and detectable in peripheral blood. The challenge has been to find the most reliable and time-sensitive cardiac enzyme(s) to reflect appropriate staging and risk stratification. Research is helpful, but clinical intervention required critical timing.

Ask most clinicians today about cardiac enzyme, cardiac injury studies, or other related markers and you’ll hear about CPK, CK-MB 1, 2, 3 and other isoenzymes, LDH electrophoresis, and of course troponins T and I. What’s more is that the reference ranges for most of these tests haven’t really changed much either. If I called you and said your patient in 706-W has a Troponin of <0.03 you might be relieved for now. If I said that same patient’s troponin was 0.560—we might have a different story unfold. But what if I told you your patient’s troponin was 13, and was trending down from 15? What do you do with that? What if I only called to report a troponin-DELTA which was 0.0? Was there an in-service you missed? Possibly. Sounds like your institution might have 5th-gen on board.

What was wrong with the old troponin?

In a word: nothing, really. This really isn’t about buy-in for a “better” test or a better detection method. This is about creating a dialogue about improving risk stratification for our patients with coronary disease. Let’s go back to Chicago, specifically the last hospital I worked in before starting medical school: Swedish Covenant Hospital. Having been through a few hospitals in my time, I can say you’d be hard pressed to find a more streamlined, albeit small community hospital, laboratory service. Running a full gamut of SIEMENS instrumentation and critical middleware-software, the management there ran a tight ship—which included critical troponins. We ran the TnI-Ultra assay on the ADVIA Centaur/XP platform. It was your standard three-part immunoassay sandwich test with a biotin-streptavidin antigen-antibody detection. It was fast, used little reagents, was relatively stable, had a great system of QC, and was calculably-flexible between heparinized and ETDA plasma samples. Two-point calibration kept it tight between (and this is from memory, loosely) 0.006 and 0.50 ng/mL, and I believe we called our critical values at 0.40 ng/mL. This was a good test, and it’s used in many labs today still. It’s got great stability and has room to interpret ACS risk stratification based on population data in each location. People understand those results, too. But exactly how much room between, let’s say 0.10 ng/mL and >0.50 ng/mL, is there to stratify that risk? Complex decision algorithms then become hybrids of institutional cardiology recommendations, American College of Cardiology (ACC) recommendations, emergency department input, and, of course, laboratory management recommendations.

Here at Bronx Care Hospital Center (BCHC), I spoke with a laboratory manager about rolling out this brand new high-sensivity troponin (hs-cTn), and we discussed their vaildation and policies. Along with this new project, the hospital has been a vocal part of American College of Cardiology ACC17 Acute and Stable Ischemic Heart Disease program addressing topics including marijuana use and ACS, stable angina risk stratification, NSTEMI sex differences in revascularization and outcomes, treating cocaine related ACS with beta blockers, and research Anticoagulation Therapy After Anterior Wall ST-Elevation Myocardial Infraction in Preventing LV Thrombi. So, it seems fitting that this is as good as any a pilot location for cardiology departments city-wide to watch and learn from the hs-cTn roll-out!

Tell me more about this new test…

This hs-cTn assay is an electrochemiluminescence immunoassay (ECLIA) that uses two monoclonal antibodies against human cardiac troponin T. At this institution, they are using this immune sandwich assay on a Roche Cobas E with a similar biotin-streptavidin coated microparticle complex as with the previous generation testing. This is a short test with similar reagent use and stability as before, and only for lithium heparinized samples. With a relatively quick turn-around in less than 10 minutes, the new hs-cTn offers critical information for clinical correlations on the fly from potential STEMI codes coming into the ED.

Without going into horrific details about validating data on old and new troponins across patient populations, there is something interesting to note here which came up in discussion with the lab manager: new reference ranges. Now, with testing sensitivity, cross-reactivity, ranges, and interfering substances, the ranges are no longer the decimal-place values reported that we’re all used to. The ranges we work with now at BCHC are cutoff between <12 ng/L for positives and >52 ng/L for critical values suggestive of acute coronary syndrome. The analytical measuring range is much larger now between 6-10,000 ng/L. With the adjustments for limits of detection and blanks on instrumentation, the specificities of these values are normalized on a larger index for reflecting differences in male and female cardiac enzyme activity to a common cutoff of that <12 ng/L value. But more so than just a value, a new part of trending troponins becomes much more important: the delta values. These are more acutely indicative of the cardiac necrosis and/or condition of other non-specific heart tissue damage en vivo occurring in patients. Taking all this into account, you now have a much wider and broader range of values to interpret and incorporate into your clinical decision making, which brought up a few questions when I spoke with lab staff as well as cardiologists.

So, what’s wrong with the new troponin?

Okay, that’s a fair question at this point. And my answer is still: probably nothing. Sorry to be so inconclusive, but it’s still early days. There is a lot of data to support moving toward newer generation hs-cTn testing since it has been available outside of FDA-approval in Europe before January 2017. Research done in the Department of Internal Medicine and Central Institute for Medical Laboratory Diagnostics at Innsbruck Medical University in Austria show that new troponins might not be that different (read: better) than their 4th generation counterparts, at least with regard to emergency room visits. T. Ploner, et. al, argue that diagnosing AMI in the ED doesn’t really benefit from the heightened sensitivity offered by the new Roche 5th gen assay (Figure 1, Figure 1). But, when they compared the detection of other cardiac disease including AMI, unstable angina, heart failure, arrythmias, pulmonary emboli, pulmonary disease, anemia, renal disease, and several other entities, the 5th generation assay could more readily detect changes early and provide clinicians with critical data quickly (Figure 1, Figure 2).

troponin-fig-1
Figure 1. Ploner et al. demonstrate here that there isn’t really any difference in the sensitivity of 4th generation vs. 5th generation troponins for detecting acute MI in the emergency room. However, there is a significant advantage in the detection of any cardiac disease, generally.
(Source: Ploner et al. (2017) High-Sensitivity cardiac tropnonin assay is not superior to its previous 4th cTnT assay generation for the diagnosis of acute MI in a real-world emergency department, link: http://spo.escardio.org/eslides/view.aspx?eevtid=48&fp=P4177)

Finally, I think a review paper from the American Journal of Medicine last year summarized it best. Coming from the Department of Cardiovascular Diseases and Department of Laboratory Medicine and Pathology at Mayo Clinic in Rochester, MN, the authors discussed concern over the troubling over-sensitivity and potential pitfalls of reaching too far with hs-cTn testing. Their bottom line: collaborating on data and accuracy between cardiology, laboratory medicine, and emergency medicine, there is a great potential for this super sensitive test to provide clinicians with very useful data in the near future. We just have to process that data correctly. As always, results should be interpreted in conjunction with clinical presentation including medical history and laboratory data. But in the case of new and coming advances in critical care, there seem to be some common themes between my conversations here at BCHC and in what I read in the literature regarding how to ensure we move forward appropriately.

  1. Multidisciplinary educational efforts are critical. The ER, the lab, and the cardiology department at each institution utilizing 5th gen troponins need to understand the new ranges, the new triaging cutoffs, the clinical correlations for consulting the ICU/CCU, and how to understand the deltas for their patient populations.
  2. Create clear communications for your laboratory values. Will you normalize for gender or provide sex-specific confidence interval reporting? Will you provide tables for suggested value correlations with AMI/ACS protocols?
  3. Order sets and in-service training. You’d be surprised how much the nitty gritty details of lab draws and ordering appropriate tests/tubes could slow down your institution’s advancement.
troponin-fig-2
Figure 2. How the authors at Mayo Clinic establish the use of new hs-cTn assays in diagnosing and triaging potential AMI patients.
(Source: Sandoval, Jaffe (2017) Using High-Sensitivity Cardiac Troponin T for Acute Cardiac Care, The American Journal of Medicine (2017) 130, 1358–1365, doi:10.1016/j.amjmed.2017.07.033)

At the very end of the day, it’s up to the institution. Clinical centers have to follow their own guidelines for cardiac pathology. ACC/ESC/AHA guidelines and Universal MI definitions are for clinical correlation across locations, but a single roll-out of a fancy new test can’t make a better ER. It really does take communication, collaboration, and accountability. We all have to push the envelope and practice at the top of our scopes in order to make health care better every day. One of the ways we might be able to do that now is by considering these new high-sensitivity troponins as a useful new clinical tool to improve patient outcomes.

Thanks for reading! See you next time!

Disclosure: I am no longer affiliated with Swedish Covenant Hospital in Chicago as an employee, and any recount of policy and/or procedure(s) specifically regarding their cardiology protocols and troponin resulting are a historical and anecdotal account of my time working there in the past. I have no affiliations with SIEMENS, Advia, Roche, or any other medical laboratory instrumentation institution. I am only affiliated with Bronx Care Hospital System as a current rotating medical student and my account of their transition to 5th gen testing is anecdotal from discussions with in-house staff, cardiologists, and laboratory management.

 

ckanakisheadshot_small

Constantine E. Kanakis MSc, MLS (ASCP)CM graduated from Loyola University Chicago with a BS in Molecular Biology and Bioethics and then Rush University with an MS in Medical Laboratory Science. He is currently a medical student at the American University of the Caribbean and actively involved with local public health.

Chemistry Case Study: Hypercalcemia in Sarcoidosis

Our patient is a 47-year-old female with a history of type II diabetes mellitus, hypertension, pancreatic insufficiency, systemic sarcoidosis with lung and liver involvement. She was admitted into the ED for severe hypercalcemia, hypokalemia and hypomagnesemia. Her total calcium concentration was at 15.1 mg/dL (ref range: 8.3-10.2 mg/dL, critical: >13.0) at admission and albumin was low. Further testing revealed 25-hydroxy vitamin D (25(OH)D) of 23.2 ng/mL, which is considered insufficient, and decreased PTH of < 15 pg/mL (ref range: 15 – 65). From these results, primary hyperparathyroidism was ruled out. PTH related peptide (PTHrp) was tested given her sarcoidosis history.

PTHrp is produced by some cancers, especially kidney, breast and lung cancers, and as well as lymphoma and leukemia. It has the same N-terminal and binds to the same receptor as PTH, therefore sharing some functions of PTH. In patients with hypercalcemia associated with malignancy, PTHrP may be evaluated. There are also case reported sarcoidosis-related hypercalcemia due to production of PTHrp. In the case, PTHrp was normal at 0.4 pmol/L (ref range: < 2.0).

Further tests showed that 1, 25-dihydroxyvitamin D (DHVD) was elevated at a concentration of 93.3 pg/mL (ref: 18.0 – 78.0). In the presence of decreased 25(OH)D, this result suggested that the 1-alpha-hydroxylase could be the cause of hypercalcemia. DHVD is the active form of vitamin D. It promotes intestinal calcium absorption and, in concert with PTH, skeletal calcium deposition. 25(OH)D converts to DHVD via 1-alpha-hydroxylase, which is almost exclusively expressed in the kidney, but can also be found in some extrarenal tissues, including inflammatory cells of the monocyte/macrophage lineage commonly seen in sarcoidosis and other granulomatous diseases. DHVD produced in extrarenal tissues is PTH-independent, and moreover, elevated calcium induced by extrarenal DHVD can inhibit PTH production via calcium-sensing receptor (CaSR) on parathyroid cells.

Sarcoidosis is a multisystem inflammatory disease of unknown etiology manifests as granulomas found predominantly in the lungs and lymph nodes. Hypercalcemia is seen in about 10-13% of patients. Overproduction of 1-alpha-hydroxylase and production of PTHrp can both contribute to the hypercalcemia in some patients with sarcoidosis. In this case, PTHrp was normal and elevated 1-alpha-hydroxylase was found to be the cause of hypercalcemia.

In addition to treatment of the underlying disorder, treatment of hypercalcemia in sarcoidosis is aimed at reducing intestinal calcium absorption and DHVD synthesis. Besides dietary interventions, glucocorticoids and bisphosphonates have also been used successfully to treat hypercalcemia in sarcoidosis:

  • Glucocorticoids: inhibit DHVD synthesis by the activated mononuclear cells (major contribution), inhibit intestinal calcium absorption and osteoclast activity
  • Bisphosphonates: inhibit the resorption of bone by osteoclasts

 

References

  1. https://emedicine.medscape.com/article/301914-overview
  2. https://www.uptodate.com/contents/hypercalcemia-in-granulomatous-diseases
  3. https://www.uptodate.com/contents/diagnostic-approach-to-hypercalcemia
  4. https://www.ncbi.nlm.nih.gov/books/NBK109831/

 

Huang

-Rongrong Huang, PhD is a first year clinical chemistry fellow at Houston Methodist Hospital. Her interests include general clinical chemistry, genetic biochemistry and applications of mass spectrometry in clinical laboratories.

Xin-small

-Xin Yi, PhD, DABCC, FACB, is a board-certified clinical chemist, currently serving as the Co-director of Clinical Chemistry at Houston Methodist Hospital in Houston, TX and an Assistant Professor of Clinical Pathology and Laboratory Medicine at Weill Cornell Medical College.

Chemistry Case Study: Conjugated Bilirubin in Neonatal Jaundice

Case History

Patient was a 1-week-old infant in the level 2 NICU born at 37 weeks. This infant was initially born with indirect hyperbilirubinemia but now also has increasingly elevated level of direct bilirubin (see measurements in table below). Neonatologist requested conjugated and unconjugated bilirubin test due to increasing elevated level of direct bilirubin. Conjugated bilirubin test is not routinely performed in our hospital laboratory and needs to be send out.

Question: What’s the difference between conjugated bilirubin and direct bilirubin? When does conjugated bilirubin need to be assessed?

Ref Range 3/6/18 3/7/18 3/9/18 3/10/18 3/12/18
Bilirubin total, neonatal 1.0-10.5 mg/dL 9.2 8.7 10.8 10.2 8.6
Bilirubin direct, neonatal 0.0 – 0.6 mg/dL 0.5 0.7 1.8 1.8 2.1

Discussion

Neonatal jaundice is commonly seen in newborns in the first few days of life, mainly due to increased bilirubin formation from break down of red blood cells and limited conjugation of bilirubin. Total bilirubin normally peaks at day 2-3 and should decline by day 4-5. Sample is collected via heelstick in green top tube and protected from light. Measurement of total bilirubin is interpreted based on the Bhutani Nomogram to assess risk of hyperbilirubinemia. Most often, unconjugated bilirubin is elevated in neonatal jaundice owing to hemolytic causes. In cases with prolonged jaundice, conjugated bilirubin needs to be determined to rule out cholestasis.

Conjugated bilirubin refers to bilirubin conjugated with one or two glucuronic acid, and this term “conjugated bilirubin” is often used interchangeably with direct bilirubin. Direct bilirubin refers to bilirubin fractions that can directly react with diazo reagent without the addition of accelerator, such as methanol or ethanol. This fraction usually includes conjugated bilirubin and delta bilirubin. Delta bilirubin is formed by covalent bonding between conjugated bilirubin and albumin, and has a similar half-life as albumin, 21 days. Therefore, direct bilirubin measurement overestimate conjugated bilirubin and in cases with persist or atypical jaundice, clear differentiation between conjugated and direct bilirubin is important. Clinician should know what the laboratory is measuring when interpreting the bilirubin fraction results.

In laboratories, conjugated bilirubin can be assessed by the VITROS BuBc dry slide, which simultaneously measures unconjugated (Bu) and conjugated (Bc) bilirubin by use of a mordant. In the presence of the mordant, the visible spectra of conjugated and unconjugated bilirubin are different, allowing measurement of both species from a single slide. Fractions of bilirubin can also be separated by HPLC, but this is not practical to use in a routine clinical laboratory. In this case, conjugated bilirubin was measured by VITROS BuBc slide test, and result came back elevated at 1.0 mg/dL (ref range: < 0.3 mg/dL).

 

Ketcham

-Megan Ketcham, MD is a 4th year anatomic and clinical pathology resident at Houston Methodist Hospital. She will be completing both hematopathology and dermatopathology fellowships. Her interests include pathology resident and medical student education and skin lymphomas.

Xin-small

-Xin Yi, PhD, DABCC, FACB, is a board-certified clinical chemist, currently serving as the Co-director of Clinical Chemistry at Houston Methodist Hospital in Houston, TX and an Assistant Professor of Clinical Pathology and Laboratory Medicine at Weill Cornell Medical College.

Is It Possible to Have Coexistence of Hepatitis B Surface Antigen and Antibody?

Hepatitis B surface antigen (HBsAg) is the serologic hallmark of acute Hepatitis B virus (HBV) infection. It can be detected in serum using immunoassays a few weeks after HBV infection, and normally disappears after 4-6 months in recovered patients (1). Antibodies against HBsAg (anti-HBs) appears as a response from the host immune system, and these antibodies neutralize HBV infectivity and clear circulating HBsAg (2). Anti-HBs generally persist in life, indicating recovery and immunity from HBV infection.

Some of us may simply assume that the presence of anti-HBs should always associated with the loss of HBsAg. However, it is possible to see concurrent anti-HBs and HBsAg in patients. In fact, coexistence of HBsAg and anti-HBs is not rare, and has been reported in 10 to 25 percent of HBV chronic carriers in previous studies (3-4).  The underlying mechanism is not fully understood but several reports explained it as HBsAg mutants escaping the immune system (2-4). HBsAg mutants are believed to arise under the selective pressure from the host immune system, or from vaccinations (4-6).

“a” determinant in HBsAg is one of the main target of anti-HBs. It has been reported that mutations in the “a” determinant of the surface gene (S-gene) result in amino acid substitutions in HBsAg, and reduce the binding of anti-HBs to HBsAg, leading to immune escape (4). The first HBV mutant was reported by Zanetti et al in 1988 as G145R mutation. In their report, infants born to HBsAg carrier mothers developed breakthrough infections despite receiving HBIG and HBV vaccine at birth (5). Since this report, several other HBsAg mutations have been reported (4, 6).

Currently, there is no easily available assay to diagnose individuals who are suspected of harboring HBsAg escape mutants. Moreover, mutated HBsAg may leads to false negativity in some serologic assays, leading to a missed diagnosis of chronic HBV infection (6). Another concern is the potential risk of transmission to others, as vaccination does not provide protection from these mutated viruses (8); this is especially important in liver transplant recipient and newborns from HBsAg positive mothers.

References

  1. Lok A, Esteban R, Mitty J. Hepatitis B virus: Screening and diagnosis. UpToDate. Retrieved Feb 2018 from https://www.uptodate.com/contents/hepatitis-b-virus-screening-and-diagnosis#H3
  2. Liu W, Hu T, Wang X, Chen Y, Huang M, Yuan C, Guan M. Coexistence of hepatitis B surface antigen and anti-HBs in Chinese chronic hepatitis B virus patients relating to genotype C and mutations in the S and P gene reverse transcriptase region. Arch Virol 2012;157:627–34.
  3. Colson P, Borentain P, Motte A, Henry M, Moal V, Botta-Fridlund D, Tamalet C, Gérolami R. Clinical and virological significance of the co-existence of HBsAg and anti-HBs antibodies in hepatitis B chronic carriers. Virology 2007;367:30–40.
  4. Lada O, Benhamou Y, Poynard T, Thibault V. Coexistence of hepatitis B surface antigen (HBs Ag) and anti-HBs antibodies in chronic hepatitis B virus carriers: influence of “a” determinant variants. J Virol. 2006 Mar;80(6):2968-75.
  5. Zanetti AR, Tanzi E, Manzillo G, Maio G, Sbreglia C, Caporaso N, Thomas H, Zuckerman AJ. Hepatitis B variant in Europe. 1988 Nov 12; 2(8620):1132-3.
  6. Leong J, Lin D, Nguyen M. Hepatitis B surface antigen escape mutations: Indications for initiation of antiviral therapy revisited. World J Clin Cases 2016;4:71.
  7. Colson P, Borentain P, Motte A, Henry M, Moal V, Botta-Fridlund D, Tamalet C, Gérolami R. Clinical and virological significance of the co-existence of HBsAg and anti-HBs antibodies in hepatitis B chronic carriers. 2007;367:30–40.
  8. Thakur V, Kazim S, Guptan R, Hasnain S, Bartholomeusz A, Malhotra V, Sarin S. Transmission of G145R mutant of HBV to an unrelated contact. J Med Virol 2005;76:40–6.

 

Xin-small

-Xin Yi, PhD, DABCC, FACB, is a board-certified clinical chemist, currently serving as the Co-director of Clinical Chemistry at Houston Methodist Hospital in Houston, TX and an Assistant Professor of Clinical Pathology and Laboratory Medicine at Weill Cornell Medical College.

A Laboratory Professional’s Perspective on the Opioid Crisis

It was in the 1980s that physicians first explored the use of narcotics/opioids for the treatment of pain associated with non-terminal illnesses, including chronic and “mild to moderate” pain. In 2012, opioid prescriptions for outpatients were common, and some states had as many as 143 opioid prescriptions for every 100 people. Today, more than 6 out of 10 drug overdoses involve an opioid. The CDC states that 91 Americans die every day from an opioid overdose. This situation has been called “the opioid crisis” and the “opioid epidemic.” It is a public health emergency.

The landscape is characterized by new trends in both the drugs involved and drug user demographics. Current data indicates that prescription opioids are not the main problem. In fact, from 2015 to 2016, prescription opioid overdoses decreased from 17,539 to 16,800. The decrease in prescription overdose may indicate that efforts to reduce over-prescribing may be working. Or, drug users may be abandoning high cost prescription opioids for illicit drugs.

While prescription opioid overdoses have been decreasing, the incidence of heroin overdose has tripled. The incidence of fentanyl overdose has increased 196%, and the incidence of overdose due to non-methadone synthetic opioids has increased by 72%. Fentanyl is available both legally by prescription, and illegally from illicit sources. It is frequently combined with or sold as other drugs such as heroin, cocaine, and alprazolam. Fentanyl is 100 times more potent than morphine, and 50-100 times more potent than heroin. Even more dangerous are the fentanyl analogs, carfetanil(yl) sufentanil, acry and acetyl fentanyl, and furanyl fentanyl, to name a few. Sufentanil is 1000 times more potent than morphine, and carfentanil – sometimes called elephant tranquilizer – is 10,000 times more potent than morphine. Opioid abuse now spans nearly all demographics. In fact, NCHS Data Brief in 2017 disclosed that the age group with the most rapid rise in opioid overdose is adults ages 55-64 years. Some of the greatest increases in heroin related deaths have been among women, privately insured, and those with higher incomes – demographic groups that historically have had low rates of heroin abuse.

Laboratory professionals can help fight this crisis by providing relevant testing, and billing for the testing appropriately. Most hospitals are ill equipped to test for the synthetic opioid analogs. For many hospitals, the drug testing capabilities consists of an immunoassay based urine drug screen. These screens can detect many of the “classic” drugs of abuse like morphine (heroin), cocaine, amphetamines, PCP, and benzodiazepines. These screens do not differentiate individual drugs in a drug class, and they can’t detect fentanyl or fentanyl analogs, even with high degrees of cross-reactivity. As our Vice President of Laboratories expressed it to me, “our emergency rooms are full of overdose patients with negative drug screens.” Unfortunately, the culprit drug is not identified until a medical examiner orders forensic toxicology. More comprehensive and confirmatory testing like mass-spectrometry based testing provides more accurate information.

Mass spectrometers are not cheap, and many laboratory professionals are challenged with obtaining funding for them. The challenge is not lessened by the bad taste left in Medicaid’s mouth by code-stacking when billing for drug testing in the pain management patient population. This practice was, unfortunately, exploited by some physicians running office-based drug testing labs. Large multi-drug LCMS based panels were used in routine monitoring of pain management testing but instead of billing per panel, the test was billed by drug (analyte) in the panel. This practice led to CMS scrutinizing the use of mass spec testing alone and recommending the limited immunoassays. Laboratory professionals have the responsibility to advocate for the appropriate use of this powerful testing, and fortunately we are doing that – the Academy of AACC in collaboration with American Academy of Pain Medicine just released guidelines for the use of laboratory tests in monitoring pain management patients. We need to be trusted to do the right test, at the right time, for the right patient.

Forensic pathologists and toxicologists also face big challenges related to the opioid crisis. Forensic toxicologists are challenged to keep up analytically with synthetic and novel drugs entering the market while dealing with the pressure of limited budgets and client frustration with long turnaround times. Forensic pathologists are challenged by the sheer volume of overdose-related deaths. The National Academy of Medical Examiners (NAME) limits the number of autopsies to 325/pathologist/year. There are currently only around 500 board certified forensic pathologists in the US and the future doesn’t look great – only 3% of graduating medical students choose to enter pathology and only 7% of those will enter forensic pathology.

 

Sarah Brown Headshot_small

Sarah Riley, PhD, DABCC, is an Assistant Professor of Pediatrics and Pathology and Immunology at Washington University in St. Louis School of Medicine. She is passionate about bringing the lab out of the basement and into the forefront of global health.  

Which Potassium Do You Believe?

A patient presented to the Emergency Department at the St. Paul’s Hospital. Initial blood was collected by phlebotomy staff (one poke) at 6:55 am in the morning and the specimen was received in the lab at 7:11 am.

Venous blood gases: Potassium  7.3 mmol/L
Plasma Lytes: Potassium  3.3 mmol/L

Emergency phoned the lab about these discrepant potassium results. What is going on?! The venous gas specimen was centrifuged and appeared hemolysed (3+), while the plasma sample had no evidence of hemolysis.

The phlebotomist indicated there was no problem with the collection. Repeat testing was initiated an hour later.

Venous blood gases: Potassium  6.4 mmol/L
Plasma Lytes: Potassium  3.6 mmol/L

The venous gas specimen was centrifuged and appeared hemolysed (3+).

Because the venous gas specimens were transported on ice and the other tubes of blood collected were sent at room temperature, the biochemist discussed the possibility of a red cell cold agglutinin with the ER physicians. The ER physicians requested evaluation for a cold agglutinin (the EDTA tube collected for early hematology was used for this analysis). Lab staff performed the screen and it was 4+ for cold agglutinin.  ER physicians were advised to believe the lower potassium results and to avoid sending further specimens on ice for this patient.

 

Lyon-small

-Dr. Andrew Lyon, PhD, FCACB, DABCC is a clinical chemist and clinical toxicologist. He is the current past-president of the Canadian Society of Clinical Chemists. He is currently Division Head of Clinical Biochemistry of the Saskatoon Health Region and teaches general pathology residents as a clinical associate professor of Pathology and Laboratory Medicine at the University of Saskatchewan.

Pitfalls of Prolactin Biochemistry Assay

Laboratories occasionally get questions from clinicians about prolactin results, mainly to either rule out high-dose hook effect or assess interference from macroprolactin. In most laboratories, sandwich immunoassay is used to measure prolactin concentration and it is widely known that older generations of prolactin assays suffer from hook effect and interference from macroprolactin. In the presence of extremely high concentration of prolactin, antibodies can be saturated, resulting in falsely low results, which is known as high-dose hook effect. Multiple cases have been reported in patients with giant prolactinomas, that their prolactin results were measured as normal or moderately elevated. In order to rule out high-dose hook effect, clinicians normally request laboratories to perform appropriate dilutions for prolactin in patients with large pituitary tumors. Newer generation of prolactin assays have better performance in this aspect, and most assays nowadays have no hook effect up to concentrations of 10,000 ng/mL, claimed by manufactures.

Another pitfall of prolactin assay is the interference from macroprolactin. Macroprolactin is a complex of prolactin bound to immunoglobulin, and thought to be biologically inactive. In the presence of elevated macroprolactin, patient is asymptomatic. However, macroprolactin can be picked up by prolactin immunoassays to some extent, and results in misdiagnosis as hyperprolactinemia. Reports showed that 15-20% of cases with hyperprolactinemia was due to elevated macroprolactin. Therefore, macroprolactinemia should be considered while evaluating hyperprolactinemia cases in the absence of symptoms or pituitary imaging evidence. Laboratories could easily perform dilution study to test if interference exists. To confirm the presence of macroprolactin, polyethylene glycol (PEG) 6000 can be used to precipitate macroprolactin followed by prolactin measurement in the supernatant. The presence of macroprolactin is suggested when the pull-down percentage is greater than 40-50%. This test is offered by many reference laboratories.

These two pitfalls of prolactin biochemistry assays should always be kept in mind by laboratorians, to provide better guidance to clinicians’ concern and workups on prolactin related cases.   

 

Xin-small

-Xin Yi, PhD, DABCC, FACB, is a board-certified clinical chemist, currently serving as the Co-director of Clinical Chemistry at Houston Methodist Hospital in Houston, TX and an Assistant Professor of Clinical Pathology and Laboratory Medicine at Weill Cornell Medical College.