Clinical Biochemistry

The overall clinical penetrance in terms of iron overload-related clinical symptoms is less than 30% in HFE-associated hereditary hemochromatosis. Ferritin is the most reliable biomarker to quantify iron load but may be falsely elevated during an acute phase response as in inflammation, stress, or infections. In the investigation of clinical hereditary hemochromatosis, don’t order HFE C282Y testing unless BOTH the ferritin and the transferrin saturation are elevated. A normal ferritin rules out a clinically treatable hemochromatosis syndrome and is therefore an appropriate first line test. Transferrin saturation can be added on to the same blood sample if the ferritin is elevated.

Sources:

Adams PC, Reboussin DM, Press RD, Barton JC, Acton RT, Moses GC, Leiendecker-Foster C, McLaren GD, Dawkins FW, Gordeuk VR, Lovato L, Eckfeldt JH. Biological variability of transferrin saturation and unsaturated iron-binding capacity. Am J Med 2007;120:999.e1-7. PMID: 17976429.

Allen KJ, Gurrin LC, Constantine CC et al. Iron-overload-related disease in HFE hereditary hemochromatosis. N Engl J Med 2008;358:221–230. PMID: 18199861.

Porto G, Brissot P, Swinkels DW et al. EMQN best practice guidelines for the molecular genetic diagnosis of hereditary hemochromatosis (HH). Eur J Hum Genet 2016;24:479-95. PMID: 26153218.

Rossi E, Olynyk JK, Jeffrey GP. Clinical penetrance of C282Y homozygous HFE hemochromatosis. Expert Rev Hematol 2008;1:205–216. PMID: 21082925.

Tarr H, Chen Y. An iron deficient patient with opposite iron profiles within five days. Clin Lab 2012;58:1331-2. PMID: 23289209.

Waalen J, Felitti VJ, Gelbart T, Beutler E. Screening for hemochromatosis by measuring ferritin levels: a more effective approach. Blood 2008;111:3373-6. PMID: 18025154.

The lifespan of a red blood cell (RBC) is approximately 90-120 days, thus the effects of a patient’s change in behaviour, diet, or newly adjusted medications will not be reflected in the HbA1c measurement until most of the previous RBCs in circulation are replaced (~90 days). Therefore, testing at time intervals earlier than 3 months does not allow enough time to pass to reach the treatment target or new steady-state. Overtesting may lead to unnecessary regimen changes, adverse effects, and higher costs. Testing at 6-month intervals may be considered when glycemic targets are consistently achieved. In pregnant patients with pre-existing diabetes, more frequent HbA1c measurements may be appropriate based on clinical guidelines (i.e. at each trimester).

Sources:

American Diabetes Association Professional Practice Committee; Glycemic Targets: Standards of Medical care in Diabetes. Diabetes Care. 2022 Jan;45 Suppl 1:S83-S96. doi: https://doi.org/10.2337/dc22-S006. PMID: 34964868.

Baek J, Rajeswaran V, Tran S, Alexander L, Jaskolka D, Usmani S, Yip P, Mukerji G. A Multimodal Intervention for Reducing Unnecessary Repeat Glycated Hemoglobin Testing. Can J Diabetes. 2022 Jun 30:S1499-2671(22)00170-8. doi: 10.1016/j.jcjd.2022.06.006. PMID: 36008251.

Driskell OJ, Holland D, Waldron JL, Ford C, Scargill JJ, Heald A, Tran M, Hanna FW, Jones PW, Pemberton RJ, Fryer AA. Reduced testing frequency for glycated hemoglobin, HbA1c, is associated with deteriorating diabetes control. Diabetes Care. 2014 Oct;37(10):2731-7. doi: 10.2337/dc14-0297. PMID: 25249670.

McCarter RJ, Hempe JM, Chalew SA. Mean blood glucose and biological variation have greater influence on HbA1c levels than glucose instability: an analysis of data from the Diabetes Control and Complications Trial. Diabetes Care. 2006 Feb;29(2):352-5. doi: 10.2337/diacare.29.02.06.dc05-1594. PMID: 16443886.

National Institute for Health and Care Excellence (NICE); Diabetes in pregnancy: management from preconception to the postnatal period. 2020 Dec.

Ohde S, Deshpande GA, Yokomichi H, Takahashi O, Fukui T, Yamagata Z. HbA1c monitoring interval in patients on treatment for stable type 2 diabetes. A ten-year retrospective, open cohort study. Diabetes Research and Clinical Practice. 2018 135, 166–171. doi: 10.1016/J.DIABRES.2017.11.013. PMID: 29155151.

Tissue transglutaminase IgA antibody (anti-tTG IgA) is the recommended first-line screening test for celiac disease as it provides the best diagnostic sensitivity and specificity. Serum IgA concentrations should be considered to rule out IgA deficiency. The addition of tissue transglutaminase IgG antibody (anti-tTG IgG), or deamidated gliadin peptide antibodies (anti-DGP IgG or IgA) in the initial screening will reduce the diagnostic performance and may cause misleading results. In particular, testing of anti-DGP antibodies result in a higher false positive rate that can lead to further unnecessary testing and/or endoscopy. Anti-tTG IgG and anti-DGP IgG testing should be reserved for individuals with IgA deficiency. Implementation of an automated reflexive algorithm in the laboratory can streamline the ordering process.

Sources:

Husby S, Koletzko S, Korponay-Szabó I, et al. European Society Paediatric Gastroenterology, Hepatology and Nutrition Guidelines for Diagnosing Coeliac Disease 2020. J Pediatr Gastroenterol Nutr. 2020 Jan;70(1):141-156. doi: 10.1097/MPG.0000000000002497. PMID: 31568151.

Husby S, Murray JA, Katzka DA. AGA Clinical Practice Update on Diagnosis and Monitoring of Celiac Disease-Changing Utility of Serology and Histologic Measures: Expert Review. Gastroenterology. 2019 Mar;156(4):885-889. doi: 10.1053/j.gastro.2018.12.010. Epub 2018 Dec 19. PMID: 30578783.

Rubio-Tapia A, Hill ID, Kelly CP, Calderwood AH, Murray JA; American College of Gastroenterology. ACG clinical guidelines: diagnosis and management of celiac disease. Am J Gastroenterol. 2013 May;108(5):656-76; quiz 677. doi: 10.1038/ajg.2013.79. Epub 2013 Apr 23. PMID: 23609613.

Renal calculi analysis is a laborious and expensive test. In Alberta, 16% of repeated renal calculi tests occurred within ~5 years (88% were repeated within 3 years). However, the repeated test only rarely demonstrated a change in stone composition (5.5% of all repeats). Similarly, the first epidemiology study of urolithiasis in New Brunswick found that 14% of renal calculi tests were repeated within 3 years, and in all cases, there was no compositional change. Both Canadian Urological Association and American College of Physicians do not recommend routinely monitoring calculi composition for recurrent stones. A calculi analysis may be repeated if there are significant systemic and/or urinary abnormalities, or patients do not respond to treatment.

Sources:

Chen VY, Chen Y. The first epidemiology study of urolithiasis in New Brunswick. Can Urol Assoc J 2021;15(7):E356-60. http://dx.doi.org/10.5489/cuaj.6888. PMID: 33382373.

Paterson R, Fernandez A, Razvi H, Sutton R. Evaluation and medical management of the kidney stone patient. Can Urol Assoc J 2010;4(6):375-9. PMID: 21191493.

Qaseem A, Dallas P, Forciea MA, Starkey M, Denberg TD; Clinical Guidelines Committee of the American College of Physicians. Dietary and pharmacologic management to prevent recurrent nephrolithiasis in adults: a clinical practice guideline from the American College of Physicians. Ann Intern Med 2014;161(9):659-67. PMID: 25364887.

Sadrzadeh SM, Orton D, Burgess E, et al. Utilization of renal calculi analyses in Calgary. Clin Biochem 2016;49:1429.

Screening for monoclonal gammopathies should only be performed in patients with unexplained “CRAB” symptoms (hyperCalcemia, Renal insufficiency, Anemia, or lytic Bone lesions) or diseases associated with monoclonal gammopathies. For such patients, serum protein electrophoresis (SPE) should be the initial screening test with follow-up immunofixation electrophoresis (IFE) if indicated. If SPE is negative, serum free light chain (SFLC) testing may be ordered since SPE/IFE + SFLC offers the best sensitivity for detection of monoclonal proteins. If SFLC testing is not available, or if amyloidosis is suspected, 24-hour urine protein electrophoresis (UPE) may be ordered with follow-up IFE if indicated. Random UPE should not be ordered as there is very limited evidence supporting its sensitivity.

Sources: 

Ansari AA, Tipu HN, Ahmed D, Farhan M. Evaluation of serum free light chain in diagnosis and monitoring of plasma cell disorders. Crit Rev Immunol 2019; 39(3): 203-210. DOI: 10.1615/CritRevImmunol.2019032260. PMID: 32421964.

Bergstrom DJ, Kotb R, Louzada ML, Sutherland HJ, Tavoularis S, Venner CP, for the Myeloma Canada Research Network Consensus Guideline Consortium. Consensus guidelines on the diagnosis of multiple myeloma and related disorders: recommendations of the Myeloma Canada Research Network Consensus Guideline Consortium. Clin Lymphoma Myeloma Leuk 2020; 20(7): e352-e367. DOI: 10.1016/j.clml.2020.01.017. PMID: 32249195.

Jenner E. Serum free light chains in clinical lab diagnostics. Clin Chim Acta 2014; 427: 15-50. DOI: 10.1016/j.cca.2013.08.018. PMID: 23999048.

McTaggart MP, Lindsay J, Kearney EM. Replacing urine protein electrophoresis with serum free light chain analysis as a first-line test for detecting plasma cell disorders offers increased diagnostic accuracy and potential health benefit to patients. Am J Clin Pathol 2013; 140(6): 890–897. DOI: 10.1309/AJCP25IHYLEWCAHJ. PMID: 24225758.

Ferritin is recognized as the most sensitive and specific marker of iron storage, and low ferritin alone is diagnostic of IDA in the general population, i.e. uncomplicated cases of IDA. The measurement of iron is a poor biomarker for IDA as it is susceptible to preanalytical factors such as diurnal variation, diet, and exercise, and ultimately does not represent iron storage. In patients with complicating comorbidities (e.g. infection, autoimmune disease, kidney disease, or cancer), ferritin is an acute phase reactant and may be falsely elevated. In this setting, ordering a fasting transferrin saturation is useful to help diagnose iron deficiency together with the ferritin result.

Sources:

Guideline for the laboratory diagnosis of functional iron deficiency; https://onlinelibrary.wiley.com/doi/10.1111/bjh.12311
Iron deficiency without anaemia: a diagnosis that matters. Clinical Medicine 2021 Vol 21, No 2: 107–13. PMID: 33762368.

Liu K, Kaffes AJ. Iron deficiency anaemia: a review of diagnosis, investigation and management. Eur J Gastroenterol Hepatol. 2011; 24(2):109-16. PMID: 22157204.

Short MW, Domagalski JE. Iron Deficiency Anemia: Evaluation and Management. Am Fam Physician. 2013 Jan 15;87(2):98-104.

WHO Guideline on use of ferritin concentrations to assess iron status in individuals and populations.

Routine biochemical screening frequently bundles redundant tests when one is sufficient from a screening, diagnostic or monitoring perspective. For example, ALT is a more specific test to detect liver injury compared to AST. AST is rarely needed if the ALT is normal, and AST should only be ordered by physicians with experience in treating liver disorders or monitoring of diagnosed liver fibrosis with a validated score (e.g. FIB-4). Creatinine alone is sufficient to check kidney function because laboratories automatically report estimated GFR; urea is often an unnecessary addition. Uncoupling bundled tests within order sets for initial screening reduces low value testing.

Sources: 

Barrett BJ, Randell EW, Mariathas HH, Mohammadi A, Darcy S, Wilson R, Brian Johnston K, Parfrey PS. The effect of laboratory requisition modification, audit and feedback with academic detailing or both on utilization of blood urea testing in family practice in Newfoundland, Canada. Clin Biochem. 2020 Sep;83:21-27. doi: 10.1016/j.clinbiochem.2020.05.008. Epub 2020 May 22. PMID: 32450078.

Mathura P, Boettger C, Hagtvedt R, Sweeney C, Williams S, Suranyi Y, Kassam N, Gill M. Reduction of urea test ordering in the emergency department: multicomponent intervention including education, electronic ordering, and data feedback. CJEM. 2022 Sep;24(6):636-640. doi: 10.1007/s43678-022-00333-w. Epub 2022 Jul 20. PMID: 35857240.

Mohammed-Ali Z, Bhandarkar S, Tahir S, et al. Implementing effective test utilization via team-based evaluation and revision of a family medicine laboratory test requisition. BMJ Open Quality 2021;10:e001219. doi:10.1136/ bmjoq-2020-001219. PMID: 33731485.

Strauss R, Cressman A, Cheung M, et al Major reductions in unnecessary aspartate aminotransferase and blood urea nitrogen tests with a quality improvement initiative BMJ Quality & Safety 2019;28:809-816. PMID: 31073091.

Direct bilirubin is a sub-component of total bilirubin. Total bilirubin assays measure both direct (conjugated and delta) and indirect (unconjugated) bilirubin. When total bilirubin is low or undetectable there is no value in measuring the direct bilirubin level. Limiting direct bilirubin testing to individuals with elevated total bilirubin has been demonstrated to decrease unnecessary testing. Additionally, implementation of a laboratory reflexive testing algorithm for infants, where direct bilirubin is automatically tested when total bilirubin is elevated, has been proposed to accelerate the identification of biliary atresia while also reducing the need for additional blood collections.

Sources:

Katzman BM and Karon BS. Test Utilization Proposal for Reflex Bilirubin Testing: Why Order Two Tests When One Will Do? J App Lab Med, July 2021;6(4):980-984. PMID: 33454760.

Lam L, Musaad S, Kyle C, and Mouat S. Utilization of Reflex Testing for Direct Bilirubin in the Early Recognition of Biliary Atresia. Clinical Chemistry, May 2017;63(5): 973–979. PMID: 28283556.

Zhang G-M and Hu Z-D. Conjugated bilirubin as a reflex test for increased total bilirubin in apparently healthy population. J Clin Lab Anal. Feb 2018;32(2):e22233. PMID: 28523701.

Urine drug tests (UDTs) have a limited but important role in managing patients with substance use disorders and should be guided by a care plan that will be meaningfully changed by the results. The unregulated drug market is encumbered by an evolving milieu of drug additives and contaminates which can complicate the interpretation of simplistic urine drug testing. In particular, testing by immunoassay without confirmation by mass spectrometry can fail to detect potent drugs that can be harmful. Immunoassays are also well known for false positives that can mislead patient management. Mass spectrometry testing delivers the most reliable and comprehensive results, but with delayed turnaround time. Clinicians that are considering drug testing should consider consulting with the laboratory for advice on choosing the best test methodology available and for help interpreting the results.

Sources:

American Society of Addiction Medicine, Appropriate Use of Drug Testing in Clinical Addiction Medicine Consensus Document.

Centre for Addition and Mental Health (CAMH), Canadian Opioid Use Disorder Guideline.

CLSI. Toxicology and Drug Testing in the Medical Laboratory. 3rd ed. CLSI guideline C52. Kyle, P.B., Fuller, D.C., Garg, U., Hammett-Stabler, C.A., Hoess, E., Johnson-Davis, K., Kapur, B.M., Langman, L.J., LeGatt, D.F., Loughmiller, D., Pesce, A., Sadek, W., Smith, M.P., Watson, I.D., Wolf, C.E., Wu, A., Zhang, Y.V. Clinical and Laboratory Standards Institute; 2017.

Jannetto PJ, Langman LJ. Using Clinical Laboratory Tests to Monitor Drug Therapy in Pain Management Patients. J Appl Lab Med. 2018 Jan 1;2(4):471-472. PMID: 33636905.

Rifai, N., Horvath, A.R., Wittwer, C.T. (2018) Tietz Textbook of Clinical Chemistry. Sixth Edition, Elseiver, St. Louis, 882-883.

Tenenbein M. Do you really need that emergency drug screen? Clin Toxicol 2009; 47: 286-91. PMID: 19514875.

Positive allergen specific IgE (sIgE) tests represent sensitization and not necessarily clinical allergy. This means that IgE against specific allergens may be detectable even when a patient is clinically tolerant of a given food or environmental allergen. The positive predictive value (PPV) of this testing is low unless the specific allergen tests are carefully chosen based on a review of the patient’s clinical history correlated to specific food and/or environmental exposures. Screening panels and indiscriminate batteries of specific allergen tests should be avoided. Positive specific allergen test results in the absence of clinical allergy lead to incorrect diagnosis of allergy, unsuitable treatment and, in the case of food allergies, inappropriate dietary restrictions with potentially negative health consequences.

Sources:

Bird JA, et al. Food allergen panel testing often results in misdiagnosis of food allergy. J Pediatr. 2015;166(1):97-100. PMID: 25217201.

Kapur S, et al. Atopic dermatitis. Allergy Asthma Clin Immunol. 2018;14(Suppl 2):43-52. PMID: 30275844.

Muraro A, et al. EAACI Food Allergy and Anaphylaxis Guidelines: diagnosis and management of food allergy. Allergy. 2014;69(8):1008-25. PMID: 24909706.

NIAID-Sponsored Expert Panel, et al. Guidelines for the diagnosis and management of food allergy in the United States: report of the NIAID-sponsored expert panel. J Allergy Clin Immunol. 2010;126(Suppl 6):S1-58. PMID: 21134576.