Book:The Comprehensive Guide to Physician Office Laboratory Setup and Operation/Primary laboratory testing domains in the POL/Hematology and blood collection
2.2 Hematology and blood collection
In July 2014, healthcare market research company Kalorama Information estimated that by volume, the hematological complete blood count (CBC) test was second only to the dipstick urinalysis in U.S. POLs. Kalorama estimated that while 75 percent of CBC tests in the country were being performed in hospitals and commercial reference labs, the other 25 percent of tests—nearly 100 million—were being realized by POLs and "near-patient clinics."[1] What was not directly mentioned by Kalorama, however, was the fact that CBC testing falls in the domain of at minimum CLIA moderate complexity testing; at the time no CLIA-waived CBC test devices yet existed. Since then, only one CLIA-waived device—the Sysmex XW-100—has become available for the POL seeking to perform CBC testing.[2] This means that without the XW-100, only 11.9 percent of all registered non-exempt POLs (as of May 2022) would be capable of offering CBC testing.[3] So where does that leave the other 88 percent of CLIA-certified labs with PPM and waiver certificates? What hematological testing is available to them outside the XW-100? That will be addressed later in the testing section.
Kalorama also noted that another hematological test is third most popular in U.S. POLs: prothrombin time (PT) and the related international normalized ratio (INR), referred to collectively as PT/INR. The market research company estimated that 20 million such tests are conducted in U.S. POLs every year.[4] PT/INR is a coagulation test used to measure the tendency for blood to clot and is a vital test for patients taking the anticoagulant Warfarin or some other type of oral anticoagulant therapy. Several dedicated handheld analyzers are available to CLIA-waived physician office laboratories wishing to conduct PT/INR testing. (See the testing section for more.)
2.2.1 Basic concepts and collection procedures
Blood is responsible for moving oxygen and nutrients to all the necessary cells of the body while also removing metabolic waste products that are formed from bodily processes. Blood is pumped through the body by the heart through the various blood vessels of the circulatory system. Arteries carry the blood away from the heart to the various parts of the bodies that contain capillaries. These tiny vessels allow water, oxygen, and chemicals to pass from the blood to the tissues and back. Veins, a third type of vessel, usher the blood from the capillaries back toward the heart. In all but the pulmonaries, arteries carry highly oxygenated blood while veins carry oxygen-depleted blood.
When blood must be collected for analysis, it will typically come from either specific veins in the antecubital area of the arm or the capillary beds of the fingers or heel, depending on the volume needed for testing. In rare cases such as respiratory emergencies, an arterial blood draw may be necessary, in which case the radial or brachial artery is used. The procedures used to draw and collect blood from these areas differ, and careful attention must be paid to handling of the blood upon collection, especially with arterial draws. Likewise, collection equipment may vary slightly depending on method and area of collection. Butterfly needles, for example, may be used for patients with small veins or for pediatric patients, while special heparinized syringes are used for arterial draws. However, safety equipment like gloves and sharps containers will always need to be used regardless of area and method, as required by the Occupational Safety and Health Administration (OSHA).[5][6]
2.2.2 Blood composition
Blood is roughly 52 to 62 percent plasma and 48 to 38 percent formed elements such as red blood cells (RBC), white blood cells (WBC), and platelets.[5] The plasma portion of blood is 92 percent water and eight percent constituents such as albumin (a protein that helps move small molecules through blood), fibrinogen (a protein that helps with clotting), and globulins (a protein that includes antibodies).[7] In times of illness or poor health, the formed elements and proteins of blood can be used as important indicators to help diagnose diseases and other ailments.
The study of blood and its constituents is called hematology, practiced in laboratories all around the world. The complete blood count (CBC) represents one of the most common hematology tests used, analyzing RBC, WBC and platelet counts; hemoglobin concentration; hematocrit; WBC differential; and three RBC indices. Suggested reference ranges for these are[5]:
- WBC count: 4,300 to 10,800/mm3
- RBC count: 4.2–5.9 x 106/mm3 for adult females; 4.6–6.2 x 106/mm3 for adult males
- platelet count: 150–450 x 103/mm3
- hemoglobin concentration: 12–16 g/dL for adult females; 13–18 g/dL for adult males
- hematocrit: 37–48 percent for adult females; 45–52 percent for adult males
- red blood cell indices: MCV of 80–100 femtoliters; MCH of 27–31 picograms/cell; MCHC of 32–36 g/dL
- WBC differential: neutrophils 54–65 percent; lymphocyte 25–110 percent; monocyte 2–8 percent; eosinophil l–4 percent; basophil 0–l percent
Plasma constituents such as albumin, fibrinogen, and globulins can also be measured with hematological testing. Abnormal results could indicate disseminated intravascular coagulation, kidney or liver disease, an inflammatory disease, an infection, or dietary issues among other things. Their reference range are[8][9][10]:
- albumin: 3.4–5.4 g/dL
- fibrinogen: 200-400 mg/dL
- globulins: serum globulin 2.0–3.5 g/dL; IgM 75–300 mg/dL; IgG 650–1850 mg/dL; IgA 90–350 mg/dL
2.2.3 Testing
For POLs with compliance and accreditation certificates (meaning they can conduct moderate- and/or high-complexity tests), CLIA-waived point-of-care (POC) hematology analyzers can of course be used. Additionally, moderate-complexity benchtop hematology analyzers capable of CBC and white blood cell differential testing give added flexibility to the physician's offerings. The caveat, though, for many such labs: while better, rapid, more convenient patient care is desirable through POC technology, the need to perform enough tests and receive sufficient reimbursement for CBC testing (or alternatively make up for any loss associated with CBC testing elsewhere in practice operations) typically must still justify the added expense.
For POLs with only a CLIA certificate of waiver, the inability to perform CBC testing may be frustrating: as of May 2022, the CBC test has only been integrated into one CLIA-waived device. Why has a CLIA-waived CBC test been so elusive? In June 2012, researchers at the Point-of-Care Testing Center for Teaching and Research described the challenges underlying creating a multiplex POC hematology device that can handle CBC testing[11]:
Currently the CLIA-waived hematology and coagulation POC devices only test for hemoglobin (Hb), hematocrit (Hct), and prothrombin time/international normalized ratio (PT/INR). The problem with these devices is the lack of multiplexing. POC coagulation and hematology devices face challenges for obtaining a waiver. These challenges include the lack of clinical needs assessment, miniaturized assays that correct for interfering substances, and assays simple enough to be combined in a multiplex platform.
Later in October 2013, Kalorama contributed its own insight into the problem of making CBC and blood differential (white blood cell count) testing waived, saying that "[w]aiving differentials under CLIA has proven problematic as even the most sophisticated analyzer commonly requires verification of automated parameters due to instrument error in classifying nucleated cells and variant leukocytes."[12]
However, outside the Sysmex XW-100, CLIA-waived handheld hemoglobin, hematocrit, and PT/INR (coagulation) analyzers still give POLs at least some hematology analysis technology if they desire it. Most if not all benefit from requiring only a finger stick for blood collection rather than a tube of venous blood. The following are examples of CLIA-waived POC hematology devices that may prove useful to the POL:
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References
- ↑ "Pillars of U.S. Physician Office Testing – Complete Blood Count (CBC)". Kalorama Information. July 2014. Archived from the original on 08 June 2015. https://web.archive.org/web/20150608041606/http://www.kaloramainformation.com/article/2014-07/Pillars-US-Physician-Office-Testing-%E2%80%93-Complete-Blood-Count-CBC. Retrieved 13 May 2022.
- ↑ Wu, Alan H B; Sellers, Jill (1 March 2019). "XW-100: First FDA CLIA-Waived CBC Analyzer Designed for Physician Office Use" (in en). The Journal of Applied Laboratory Medicine 3 (5): 839–846. doi:10.1373/jalm.2018.027383. ISSN 2576-9456. https://academic.oup.com/jalm/article/3/5/839/5603132.
- ↑ Centers for Medicare and Medicaid Services, Division of Laboratory Services (May 2022). "Enrollment, CLIA exempt states, and certification of accreditation by organization" (PDF). https://www.cms.gov/Regulations-and-Guidance/Legislation/CLIA/Downloads/statupda.pdf. Retrieved 13 May 2022.
- ↑ "Pillars of U.S. Physician Office Testing – Prothrombin Time (PT/INR)". Kalorama Information. July 2014. Archived from the original on 20 March 2016. https://web.archive.org/web/20160320172826/http://www.kaloramainformation.com/article/2014-07/Pillars-US-Physician-Office-Testing-%E2%80%93-Prothrombin-Time-PTINR. Retrieved 13 May 2022.
- ↑ 5.0 5.1 5.2 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.
- ↑ 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.
- ↑ "Plasma". Blood Components. The American National Red Cross. https://www.redcrossblood.org/donate-blood/how-to-donate/types-of-blood-donations/blood-components.html. Retrieved 13 May 2022.
- ↑ "Albumin - blood (serum) test". MedlinePlus. National Institutes of Health. 24 January 2021. https://medlineplus.gov/ency/article/003480.htm. Retrieved 16 May 2022.
- ↑ "Fibrinogen blood test". MedlinePlus. National Institutes of Health. 19 January 2021. https://medlineplus.gov/ency/article/003650.htm. Retrieved 16 May 2022.
- ↑ "Serum globulin electrophoresis". MedlinePlus. National Institutes of Health. 6 February 2020. https://medlineplus.gov/ency/article/003544.htm. Retrieved 16 May 2022.
- ↑ Curtis, Corbin M.; Kost, Gerald J.; Louie, Richard F.; Sonu, Rebecca J.; Ammirati, Erika B.; Sumner, Stephanie (June 2012). "Point-Of-Care Hematology and Coagulation Testing In Primary, Rural Emergency, and Disaster Care Scenarios". Point Care 11 (2): 140–145. doi:10.1097/POC.0b013e31825a9d3a.
- ↑ "On the Prospect of CLIA-Waived Differentials". Kalorama Information. October 2013. Archived from the original on 09 June 2015. https://web.archive.org/web/20150609211746/http://www.kaloramainformation.com/article/2013-10/Prospect-CLIA-Waived-Differentials. Retrieved 13 May 2022.
