Editors: Olga Pozdnyakova, MD, PhD, Geoffrey Wool, MD, PhD, David Bernard, MD, PhD & Raul S. Gonzalez, MD
Q. When performing a manual platelet estimate from a sodium citrate tube because of EDTA-induced clumping, do you still multiply the result by 1.1, even if you are not using an analyzer to perform the estimate?
A. The 1.1 correction factor should not be applied when performing a manual platelet estimate on a sodium citrate specimen. The manual method is a microscopic estimation based on counting the average number of platelets per oil-immersion field, not a volumetric measurement. Because this visual method does not depend on the total blood volume in the collection tube, the dilution effect from the citrate anticoagulant does not alter the estimate. No regulatory or professional guidelines mandate that the dilution factor be applied to manual platelet estimates.
In contrast, when a platelet count is obtained on an automated analyzer using a sodium citrate tube, the 1.1 correction factor is necessary. Sodium citrate tubes contain approximately one part anticoagulant to nine parts blood (1:9 ratio), which dilutes the blood by about 10 percent. The analyzer reports platelet concentration per unit volume of the diluted specimen, so applying the multiplier corrects the value to reflect the true concentration of whole blood. Without this adjustment, automated counts from citrate samples would appear roughly 10 percent lower than their EDTA equivalents.
It is important to emphasize that a manual platelet estimate provides an approximate assessment of platelet quantity rather than an exact count. The result should be interpreted within clinically meaningful ranges rather than as a precise number. For example: <5 K, 5–10 K, 11–20 K, 21–50 K, 51–100 K, 101–150 K, >150 K.
Alternatively, a qualitative interpretation may be used, such as “decreased,” “normal,” or “increased.” This approach allows clinicians to make practical decisions without relying on an exact numerical value, especially when rapid interpretation is needed or automated counts are unavailable.
Gulati G, Uppal G, Gong J. Unreliable automated complete blood count results: causes, recognition, and resolution. Ann Lab Med. 2022;42(5):515–530.
Daniel Dees, DCLS, MLS(ASCP)CM
Medical Director, Clinical Hematology
Brigham and Women’s Hospital
Instructor of Pathology
Harvard Medical School
Boston, Mass.
Member, CAP Hematology/
Clinical Microscopy Committee
Q. How is Helicobacter pylori 13C urea breath testing regulated in clinical laboratories?
A. H. pylori breath testing involves somewhat unique regulatory considerations. A number of H. pylori 13C urea breath tests are approved as class I devices by the FDA (under FDA product code MSQ).
What can be confusing is that the Clinical Laboratory Improvement Amendments of 1988 describe clinical laboratories as facilities that examine “materials derived from the human body,” and the Department of Health and Human Services has stated that it “has not yet determined how breathalyzers and other tests which do not derive a specimen from the human body will be dealt with under CLIA.”1,2 Therefore, these tests are currently not subject to CLIA oversight, although clinical laboratories certainly are.2 A notice of proposed rulemaking with a public comment period would likely be required if CMS were to change its perspective on breath testing relative to CLIA classification.
It is important to emphasize that not being subject to CLIA oversight is not the same as CLIA-waived testing, which has its own clearly defined requirements.3 In alignment with CMS statements on breath testing, H. pylori breath testing (with a nonradioactive isotope such as 13C) is on the list of tests excluded from CLIA edits in the CPT coding process for laboratory reimbursement.4
So what are clinical laboratories’ responsibilities when conducting H. pylori breath testing? Per federal regulations, when clinical laboratories conduct nonwaived testing, they must adhere to applicable analytic system requirements, including having a written procedure, following test system requirements and the standard for verifying performance specifications, conducting maintenance and function checks, following biannual calibration/calibration verification procedures, and having control procedures to monitor accuracy and precision.5
CAP accreditation requires proficiency testing enrollment or at least semiannual alternative performance assessment for all tests or analytes. Enrollment in the CAP’s H. pylori Breath Test (HPBT) program is one option to address PT/APA requirements.
1. Certification of Laboratories. 42 USC §263a(a) (2025). www.govinfo.gov/content/pkg/USCODE-2011-title42/pdf/USCODE-2011-title42-chap6A-subchapII-partF-subpart2-sec263a.pdf
2. Office of Survey and Certification, HSQB. Guidance on the applicability of the Clinical Laboratory Improvement Amendments of 1988 (CLIA) to substance abuse testing [memo]. U.S. Dept. of Health and Human Services. Feb. 5, 1993. www.cms.gov/medicare/provider-enrollment-and-certification/survey
certificationgeninfo/downloads/scletter08-35.pdf
3. Waived Tests. Centers for Disease Control and Prevention. www.cdc.gov/lab-quality/php/waived-tests/index.html
4. Centers for Medicare and Medicaid Services. Adjudication of laboratory tests that are excluded from Clinical Laboratory Improvement Amendment (CLIA) edits [memo]. U.S. Dept. of Health and Human Services. April 22, 2011. www.cms.gov/Regulations-and-Guidance/Guidance/Transmittals/downloads/R882OTN.pdf
5. Condition: Analytic Systems. 42 CFR §493.1250 (1992). www.ecfr.gov/current/title-42/chapter-IV/subchapter-G/part-493
Jonathan R. Genzen, MD, PhD, MBA
Professor, Department of Pathology
University of Utah School of Medicine
Chief Medical Officer, ARUP Laboratories
Salt Lake City, Utah
Advisor, CAP Clinical Chemistry
Committee
Colleen W. Robley, MLS(ASCP)
Quality and Regulatory Affairs
Senior Specialist, ARUP Laboratories
Salt Lake City, Utah
Maryam Salehi, PhD
Assistant Professor
Department of Pathology and
Laboratory Medicine
Emory University/Grady Health System
Atlanta, Ga.
David M. Manthei, MD, PhD
Associate Professor
Department of Pathology
University of Michigan
Ann Arbor, Mich.
Chair, CAP Clinical Chemistry Committee