Residency · Residency · Pathology
Point-of-Care Testing and Quality Assurance
Introduction
Point-of-care testing (POCT) refers to laboratory testing performed near or at the site of patient care, outside the traditional central laboratory. While POCT offers rapid turnaround times and clinical convenience, it introduces unique quality assurance challenges. The pathologist and laboratory director bear regulatory responsibility for all POCT within the institution.
Common POCT Applications
POCT encompasses a wide range of tests. Glucose monitoring is the most widely performed, used in both inpatient and outpatient settings. Blood gas analysis with ABG/VBG analyzers serves the ICU, OR, and ED. Coagulation testing includes INR/PT for warfarin management and ACT in cardiac surgery. Cardiac biomarkers such as troponin and BNP can be measured at the bedside. Other common applications include urinalysis by dipstick, rapid infectious disease tests for influenza, RSV, Strep A, COVID-19 antigen, and HIV, pregnancy testing with urine hCG, portable hemoglobin/hematocrit analyzers, and creatinine for pre-contrast assessment.
CLIA Waived Testing
Tests classified as CLIA-waived carry low risk of erroneous results when performed as directed and require a Certificate of Waiver from CMS. Common examples include urine dipstick, glucose meters, rapid strep tests, and urine pregnancy tests. Despite the waived status, quality management is still required by accrediting organizations.
Advantages and Limitations
Advantages
POCT provides rapid turnaround time, delivering results in minutes versus hours. It requires reduced sample volumes since capillary specimens can be used. It improves clinical workflow in critical care settings and decreases certain pre-analytical errors because there is no specimen transport and minimal processing.
Limitations
POCT carries a higher cost per test compared to central laboratory analyzers. Operator variability is a concern because testing is performed by nursing, respiratory therapy, or other non-laboratory personnel. The menu is limited and throughput is lower than automated central analyzers. There is potential for pre-analytical errors from improper specimen type, underfilling, or hemolysis. Connectivity challenges may mean results do not automatically integrate with the LIS or EMR.
Quality Assurance Framework
Personnel and Training
All POCT operators must undergo initial training and periodic competency assessment. Competency is evaluated through direct observation, written examinations, review of QC records, and proficiency testing. Training documentation must be maintained for regulatory compliance.
Quality Control (QC)
Liquid QC is run at defined intervals such as each shift, daily, or with each new lot or shipment. Electronic QC (eQC) consists of built-in device checks, but it does not replace liquid QC per most accreditation standards. QC results must be reviewed before patient results are reported, and Westgard rules or equivalent criteria are applied to evaluate QC acceptability.
Proficiency Testing (PT)
PT is required for all non-waived POCT. Samples from external PT programs such as CAP are analyzed by the same operators using the same devices, and results are compared against peer group performance. Failure to participate or persistent PT failures can result in loss of accreditation.
Connectivity and Data Management
POCT results should be transmitted to the laboratory information system (LIS) and electronic medical record (EMR). Middleware solutions manage device connectivity, operator lockout, QC enforcement, and result review. Unconnected devices require manual documentation, which increases error risk. Operator identification and patient identification must be verified at the time of testing.
Glucose Meter Considerations
FDA-cleared glucose meters are validated for specific specimen types including capillary, venous, and arterial blood. Known interferences include hematocrit extremes, maltose from icodextrin dialysis, acetaminophen, and ascorbic acid. Critically ill patients may have unreliable capillary glucose readings due to poor perfusion. CMS glucose meter accuracy requirements specify results within 12 mg/dL for values at or below 75 mg/dL and within 15% for values above 75 mg/dL.
Blood Gas POCT
Blood gas testing has specific pre-analytical requirements including anaerobic collection, immediate analysis, and proper mixing with heparin. Calculated values such as bicarbonate, base excess, and oxygen saturation depend on measured parameters. Calibration verification and correlation with central laboratory analyzers must be documented. Temperature correction may be needed for hypothermic patients.
Regulatory Oversight
CLIA establishes federal requirements for all laboratory testing including POCT. CAP, the Joint Commission, and COLA are accrediting organizations with specific POCT standards. The laboratory medical director is responsible for POCT oversight even when testing occurs outside the laboratory. State regulations may impose additional requirements beyond federal standards.
Clinical Pearls
POCT convenience does not eliminate the need for rigorous quality management. Operator competency is the weakest link in POCT quality, and ongoing assessment is essential. Glucose meter results in critically ill patients should be confirmed with central laboratory testing when clinical decisions depend on the result. Connectivity solutions that enforce operator lockout and QC compliance dramatically reduce POCT errors.
References
- Nichols JH, et al. AACC guidance document on management of point-of-care testing. J Appl Lab Med. 2020;5(4):762-770.
- CAP Laboratory Accreditation Program. Point-of-Care Testing Checklist. College of American Pathologists; 2023.
- Kost GJ. Principles and Practice of Point-of-Care Testing. Lippincott Williams & Wilkins; 2002.
- Klonoff DC. Point-of-care blood glucose meter accuracy in the hospital setting. Diabetes Spectr. 2014;27(3):174-179.
For the intern
At 3am, if a POCT device fails QC, stop using it immediately and call the lab. Send samples to the central laboratory until the device is back in service. If a glucose meter shows a critical value that doesn't match the clinical picture, confirm with a stat central lab glucose before adjusting insulin. Document every POCT result in the EMR—never rely on memory or paper notes. Most other POCT issues (device maintenance, competency assessments, connectivity problems) can wait until morning when the laboratory director or POCT coordinator is available.
Common pitfalls
- Running patient samples when QC has failed or hasn't been performed. Always verify QC is acceptable before reporting any patient result. Most accrediting bodies require QC review before patient testing.
- Assuming CLIA-waived means no quality requirements. Even waived tests need operator competency documentation, QC when recommended by the manufacturer, and proper result documentation.
- Using capillary glucose in shock or severe hypotension. Poor peripheral perfusion makes fingerstick values unreliable—send a venous sample to the central lab instead.
- Forgetting that the lab director owns POCT quality even though nurses or respiratory therapists perform the testing. When in doubt about proper procedure, call the lab for guidance rather than improvising.
Make it stick
Imagine you’re on call and a nurse calls about a critical point-of-care testing (POCT) glucose result that doesn't fit the patient’s clinical picture. Your immediate response should be to recommend a confirmatory central laboratory venous blood glucose test. This scenario highlights the critical role of understanding POCT limitations, especially in critically ill patients where peripheral perfusion can affect results. Remember, while POCT offers rapid results, it's not without its quirks, and the central lab often serves as the ultimate arbiter for suspicious findings. Always integrate clinical context with lab data.
If you remember one thing
Always confirm critical or discordant point-of-care results with central laboratory testing, especially in unstable patients, and never perform patient testing on a POCT device that has failed quality control.