971 - Unmasking the Undetectable: Identifying and Troubleshooting a Series of Falsely Elevated HIV Viral Load Results in a Group of Patients in a Community Clinic in San Antonio, Texas

Background: Using effective antiretroviral therapy to consistently suppress plasma HIV RNA levels to < 200 copies/mL is known to improve morbidity and mortality at all stages of HIV infection and prevent transmission to sexual partners. Logistical challenges such as transporting, processing, and storing samples may threaten the accuracy of the test results. Plasma Preparation tubes (PPT) or Ethylene Diamine Tetra Acetic Acid (EDTA) tubes can be used for this test. PPT tubes contain an inert gel that migrates during centrifugation, forming a barrier between the plasma and cellular elements. Adequate separation of cellular elements may not always occur, and this can result in falsely elevated HIV Viral load (VL) due to measurement of integrated intracellular virus. It is therefore routine practice to centrifuge samples twice when PPT tubes are used. This is not necessary with EDTA tubes. In addition, there are reports that HIV RNA levels may be higher with PPT tubes are used, compared to EDTA tubes.

Methods: This is a quality improvement project that reviews a series of falsely elevated HIV VL in a group of patients who reported adherence and had been previously virologically suppressed.

Results: A total of 20 unexpectedly elevated HIV VL were identified from January to March of 2020 after introduction of a new phlebotomist in our clinic. VL ranged from 200-2530 copies/ml. Most patients (18/20) had history of virologic suppression and reported adherence. We standardized our process by using only PPT tubes and centrifuging samples twice prior to processing. Our nurses reported visible residual cellular elements in some of the plasma specimens in the tubes even after appropriate centrifugation. We continued to see suspected erroneous results. We repeated the test in EDTA tubes. 16/19 had HIV VL < 20, the remainder ranged from 27-41 copies/ml. We then implemented the use of EDTA tubes in all samples. No further cases of falsely elevated VL have been seen since the change.Table 1


Conclusion: We describe potential steps that can interfere in the accuracy of HIV VL results. Detailed review of past history and patient’s adherence to treatment is essential to identify systemic problems that may lead to errors.  Close communication with staff and laboratory provider will be key to overcome such challenges.