Book:The Comprehensive Guide to Physician Office Laboratory Setup and Operation/Primary laboratory testing domains in the POL/Clinical chemistry

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2.3 Clinical chemistry

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In July 2014, healthcare market research company Kalorama Information estimated that by volume, "clinical chemistry panels and parameters represent the fourth-most commonly performed test in U.S. POLs."[1] These panels and parameters are used to make qualitative and quantitative assessments of the level of chemical elements dissolved in body fluids such as serum, plasma, and urine as well as cerebrospinal, synovial, pleural, pericardial, and peritoneal fluids.[2][3] Clinical chemistry tests are useful for checking glucose, cholesterol, electrolytes, thyroid-stimulating hormone, or creatinine in blood plasma, serum, or urine. The presence of these analytes and others (listed in the section of fluid composition) in quantities outside a lab's standard reference ranges could indicate disease processes like diabetes, hyperlipidemia, and hypothyroidism as well as kidney, liver, and heart dysfunction.

2.3.1 Basic concepts and collection procedures

As most testing in clinical chemistry is done using blood and urine, the collection information presented in the urinalysis and hematology sections is also relevant to clinical chemistry testing. When collecting blood for testing, the type of blood collected will depend on the testing device and the type of test performed. Most modern blood glucose test devices are handheld and require only capillary blood which can be obtained using a lancet, a tiny scalpel-like device used to prick the skin of a fingertip or the heel of a foot. This blood is collected either after the patient has fasted or has eaten a full meal. The process is typically the same for some of the handheld lipid testing devices. However, more advanced metabolic, electrolyte, and lipid panels will usually require a larger sample, necessitating venous blood collected from the antecubital area of the arm. While whole blood may be used for a few clinical chemistry tests, plasma or, to a lesser extent, serum that has been separated by centrifugation is most frequently used for testing.[3] If a whole blood sample isn't sufficiently centrifuged, "it may result in an incomplete gel barrier, and the content of serum and plasma separators may produce significant analytical interference."[4] Other preanalytical errors such as hemolysis (the damaging of red blood cells during or after collection), lipemia (an excess of lipoproteins often caused by not fasting appropriately), and incorrect tube use or collection timing can also cause a sample to become unsuitable for testing.[3]

2.3.2 Fluid composition

Like urinalysis and hematological testing, clinical chemistry looks at body fluids and determines qualitatively and/or quantitatively their constituents. Clinical laboratories set reference ranges for the chemical elements found in those body fluids, and when a sample shows one or more test results outside of those reference ranges, the abnormality is often a sign of an ailment or problem in the body or with a diet.

Diabetes mellitus (DM) is such a disorder, one in which glucose is not properly metabolized due to inadequate production or use of insulin. It can also occur when the body is unable to produce enough effective insulin for the movement of glucose into body tissues. The two tests recommended by the American Diabetes Association for identifying diabetes or prediabetes is the fasting plasma glucose (FPG) and the oral glucose tolerance test (OGTT). FPG samples are usually taken in the morning after a patient has been fasting for 10 to 14 hours, while the OGTT is performed after the FBG, requiring a patient be given either a large meal or a high glucose drink and then rested for two hours. In both cases, glucose levels are tested.[2][3]

Suggested reference ranges for glucose levels include[3][5]:

  • Normal: fasting plasma glucose of 70–100 mg/dL, with a two-hour postprandial glucose of less than 140 mg/dL
  • Prediabetes: fasting plasma glucose of 101–125 mg/dL, with a two-hour postprandial glucose of 141–199 mg/dL
  • Diabetes: fasting plasma glucose of 126 mg/dL or greater, with a two-hour postprandial glucose of 200 mg/dL or greater

Of course, glucose isn't the only chemical element examined in clinical chemistry. Other common chemical elements may be tested for with cholesterol and chemistry analyzers, and their suggested reference ranges include[3][6][7][8][9][10][11][12][13]:

  • albumin (Alb), a plasma constituent made by the liver: 3.4–5.4 g/dL
  • alkaline phosphatase (ALP), a phosphate removing enzyme: 42–136 U/L
  • alanine aminotransferase (ALT), a biomarker for measuring liver health: ~4–36 U/L
  • aspartate aminotransferase (AST), a biomarker for measuring liver health: ~8-33 U/L
  • bilirubin, total (TBili), a product of heme catabolism: 0.3–1 mg/dL
  • blood urea nitrogen (BUN), an indicator for renal health: 6–20 mg/dL
  • brain natriuretic peptide (BNP), a polypeptide secreted by the ventricles of the heart: 0–100 ng/L (pg/mL)
  • calcium (Ca), vital to many functions of human biology: 8.2–10.5 mg/dL
  • carbon dioxide (CO2), an end product of cellular respiration: 22–30 mEq/L
  • chloride (Cl), which helps maintain proper body water distribution and extracellular osmotic pressure: 96–106 mEq/L
  • cholesterol, total (Chol), an essential structural component of animal cells: less than 200 mg/dL
  • creatinine (Creat), an endogenous byproduct of muscle creatine metabolism: 0.6–1.2 mg/dL
  • creatine kinase (CK), a marker of damage to muscular and renal functions: 55–170 U/L
  • high-density lipoprotein (HDL), which can remove and transport fat molecules around the body: greater than 40–50 mg/dL
  • lactate dehydrogenase (LDH), a common enzyme that acts as a marker of common injuries and disease: 105–333 IU/L
  • low-density lipoprotein (LDL), which can transport and deposit fat molecules around the body: less than 100 mg/dL
  • myoglobin, a protein that acts as a marker of muscle damage: 25–72 ng/mL
  • potassium (K), vital to proper neuron function and osmotic equilibrium: 3.5–5.0 mEq/L
  • sodium (Na), vital to osmotic equilibrium in the body: 136–145 mEq/L
  • thyroid-stimulating hormone (TSH), which prompts the thyroid gland to produce thyroxine: 0.5–5.0 µU/mL
  • thyroxine (T4), which helps regulate metabolism: 4.5–11.2 µg/dL
  • triglyceride (Trig), which enables adipose fat and blood glucose to transfer to and from the liver: less than 150 mg/dL
  • triiodothyronine (T3), which affects numerous physiological processes: 75–220 ng/dL

2.3.3. Testing

As mentioned in the hematology section, with only 11.9 percent of registered non-exempt POLs having CLIA compliance or accreditation certificates, most POLs wanting to perform in-house clinical chemistry tests will be limited to a few CLIA-waived options. Glucose testing is the most common of such tests, relying on one of more than 100 easy-to-use handheld CLIA-waived monitors that can analyze a tiny amount of capillary blood for glucose or glycosylated hemoglobin (Hb A1c). Cholesterol and lipid testing is another common type of CLIA-waived testing that can be performed in the POL, testing basic cholesterol levels or running complete lipid profiles.[3] To a much lesser degree, CLIA-waived clinical chemistry tests like metabolic, electrolyte, and liver panels can be performed on a handful of analyzers like the Piccolo Xpress from Abaxis, the i-STAT from Abbott Point of Care, and the SPOTCHEM EZ from Arkray.[14][15][16] For POL labs with moderate- and high-complexity CLIA test certification, larger, more advanced clinical chemistry analyzers like the ACE Alera from Alfa Wassermann and the ABX Pentra 400 and Pentra C200 from HORIBA provide more complex test panels and greater batch testing of patient specimens.[17][18]

In 2015, Kalorama expected modest growth from an otherwise mature global clinical chemistry test market[19], predicting market growth in the U.S. POL market was expected to be minimal through 2020. The research company said that "[p]rohibitive factors to the expansion of the U.S. POL clinical chemistry market include the lack of growth in the number of CLIA compliance (moderate- and high-complexity) POLs, centralization of core lab testing, and declining reimbursement for heavily automated tests."[1] Seven years later, all but declining reimbursement have likely affected clinical chemistry growth in the POL; the percentage of POLs running PPM certificates has dropped more than nine percent since 2011[20][21], and the consolidation of physician practices into large healthcare systems with core testing[22][23] certainly hasn't helped. But, as Kalorama points out in 2022, with the addition of more esoteric tests (e.g., natriuretic peptide tests[24] and neutrophil counts[25]) into the CLIA-waived point-of-care testing market over the past five to 10 years[24], the clinical chemistry options for existing POLs continue to expand.

You can find an extensive listing of CLIA-waived POL instrument and test kit vendors (including for the elements mentioned above) in the Additional Resources section of this guide.

References

  1. 1.0 1.1 "Pillars of U.S. Physician Office Testing – Clinical Chemistry". Kalorama Information. July 2014. Archived from the original on 01 June 2016. https://web.archive.org/web/20160601185017/http://www.kaloramainformation.com/article/2014-07/Pillars-US-Physician-Office-Testing-%E2%80%93-Clinical-Chemistry. Retrieved 13 May 2022. 
  2. 2.0 2.1 Garrels, Marti; Oatis, Carol S. (2014). Laboratory and Diagnostic Testing in Ambulatory Care: A Guide for Healthcare Professionals (3rd ed.). Elsevier Health Sciences. pp. 368. ISBN 9780323292368. https://books.google.com/books?id=LM9sBQAAQBAJ. Retrieved 13 May 2022. 
  3. 3.0 3.1 3.2 3.3 3.4 3.5 3.6 Lieseke, Constance L.; Zeibig, Elizabeth A. (2012). Essentials Of Medical Laboratory Practice. F. A. Davis. pp. 539. ISBN 9780803630352. https://books.google.com/books?id=IX_2AAAAQBAJ&pg=PA1. Retrieved 13 May 2022. 
  4. Lippi, Giuseppe; Salvagno, Gian Luca; Montagnana, Martina; Guidi, Gian Cesare (2007). "Preparation of a Quality Sample: Effect of Centrifugation Time on Stat Clinical Chemistry Testing". LabMedicine 38 (3): 172–176. doi:10.1309/D8TJCARUW575CXYH. 
  5. Riley, L.. "Mean fasting blood glucose". The Global Health Observatory. World Health Organization. https://www.who.int/data/gho/indicator-metadata-registry/imr-details/2380. Retrieved 16 May 2022. 
  6. "Albumin - blood (serum) test". MedlinePlus. National Institutes of Health. 24 January 2021. https://medlineplus.gov/ency/article/003480.htm. Retrieved 16 May 2022. 
  7. "Alanine transaminase (ALT) blood test". MedlinePlus. National Institutes of Health. 24 January 2021. https://medlineplus.gov/ency/article/003473.htm. Retrieved 16 May 2022. 
  8. "Aspartate aminotransferase (AST) blood test". MedlinePlus. National Institutes of Health. 24 January 2021. https://medlineplus.gov/ency/article/003472.htm. Retrieved 16 May 2022. 
  9. "BUN - blood test". MedlinePlus. National Institutes of Health. 1 May 2021. https://medlineplus.gov/ency/article/003474.htm. Retrieved 16 May 2022. 
  10. "HDL: The "Good" Cholesterol". MedlinePlus. National Institutes of Health. 27 February 2019. https://medlineplus.gov/hdlthegoodcholesterol.html. Retrieved 16 May 2022. 
  11. "Lactate dehydrogenase test". MedlinePlus. National Institutes of Health. 6 February 2020. https://medlineplus.gov/ency/article/003471.htm. Retrieved 16 May 2022. 
  12. "Myoglobin blood test". MedlinePlus. National Institutes of Health. 24 January 2021. https://medlineplus.gov/ency/article/003663.htm. Retrieved 16 May 2022. 
  13. "TSH test". MedlinePlus. National Institutes of Health. 26 January 2020. https://medlineplus.gov/ency/article/003684.htm. Retrieved 16 May 2022. 
  14. "Panels". Abaxis, Inc. https://www.abaxis.com/medical/piccolo/panels. Retrieved 13 May 2022. 
  15. "i-STAT 1". Abbott. https://www.globalpointofcare.abbott/en/product-details/apoc/i-stat-system-us.html. Retrieved 13 May 2022. 
  16. "SPOTCHEM EZ". Arkray USA. https://www.arkrayusa.com/clinical-diagnostics/products/spotchem-ez. Retrieved 13 May 2022. 
  17. "ACE Alera Clinical Chemistry System". Alfa Wassermann, Inc. https://www.alfawassermannus.com/acealera.asp. Retrieved 13 May 2022. 
  18. "Clinical Chemistry". HORIBA, Ltd. https://www.horiba.com/usa/medical/products/clinical-chemistry/. Retrieved 13 May 2022. 
  19. "Kalorama: New Tests, Demographics Provide Revenue Growth in Clinical Chemistry". PR Newswire. PR Newswire Association LLC. 15 April 2015. Archived from the original on 25 October 2015. https://web.archive.org/web/20151025113201/http://www.prnewswire.com/news-releases/kalorama-new-tests-demographics-provide-revenue-growth-in-clinical-chemistry-300063531.html. Retrieved 13 May 2022. 
  20. Centers for Medicare and Medicaid Services, Division of Laboratory Services (March 2022). "Enrollment, CLIA exempt states, and certification of accreditation by organization" (PDF). http://www.cms.gov/Regulations-and-Guidance/Legislation/CLIA/Downloads/statupda.pdf. Retrieved 17 April 2022. 
  21. Centers for Medicare and Medicaid Services, Division of Laboratory Services (June 2011). "Enrollment, CLIA exempt states, and certification of accreditation by organization" (PDF). Archived from the original on 10 April 2012. https://web.archive.org/web/20120410205216/http://www.cms.gov/Regulations-and-Guidance/Legislation/CLIA/Downloads/statupda.pdf. Retrieved 17 April 2022. 
  22. Thill, M. (October 2020). "Selling Moderate Complexity". Repertoire. https://repertoiremag.com/selling-moderate-complexity.html. Retrieved 17 April 2022. 
  23. Slomlany, M. (25 October 2021). "The Diagnostic Laboratory Space: An Ecosystem in Transformation" (PDF). Marwood Group Advisory, LLC. https://www.marwoodgroup.com/wp-content/uploads/2021/10/The-Diagnostic-Laboratory-Space-An-Ecosystem-in-Transformation.pdf. Retrieved 17 April 2022. 
  24. 24.0 24.1 "The Worldwide Market for Point-of-Care (POC) Diagnostic Tests, 9th Edition". Kalorama Information. 28 April 2022. https://kaloramainformation.com/product/the-worldwide-market-for-point-of-care-poc-diagnostic-tests-9th-edition/. Retrieved 16 May 2022. 
  25. Tandon, T. (21 April 2022). "Announcing the landmark FDA Clearance of the Athelas Home". Athelas, Inc. https://www.athelas.com/insights/athelas-home-announcement. Retrieved 17 May 2022.