For laboratories that do not follows CDC testing algorithm guidelines, each false-positive screening result represents a potential opportunity for a HIV misdiagnosis.Even in laboratories with proper procedures in place, false-positive results have consequences for the patients and for the cost-effectiveness of laboratory operations.9-11,18 As per CDC HIV testing guidelines, all positive screening results should be retested, which leads to additional use of technologist time and reagents. After this additional testing is performed and reviewed appropriately, only then can an appropriate final laboratory diagnosis be rendered that meets the standard of laboratory care.
Cost Savings
As observed at CMJCVAMC, the use of a fourth-generation assay with increased sensitivity/specificity led to a reduction in these false-positive results, which improved laboratory efficiency and avoided wasted resources for confirmatory tests.11,18 Cost savings at CMJCVAMC from the implementation of the fourth-generation assay would include technologist time and reagent cost. Generalizable technologist time costs at any institution would include the time needed to perform the confirmatory HIV-1/HIV-2 antibody differentiation assay (slightly less than 1 hour at CMJCVAMC per specimen) and the time needed to perform the viral load assay (about 6 hours to run a batch of 24 tests at CMJCVAMC). We calculated that confirmatory testing cost $184.51 per test at CMJCVAMC. Replacing the third-generation assay with the more sensitive and specific fourth-generation test saved an estimated $3,875 annually. This cost savings does not even consider savings in the pathologist/director’s time for reviewing HIV results after the completion of the algorithm or the clinician/patient costs or anxiety while waiting for results of the confirmatory sequence of tests.
As diagnosis of HIV can have a significant psychological impact on the patient, it is important to ensure the diagnosis conveyed is correct.27 The provision of an HIV diagnosis to a patient has been described as a traumatic stressor capable of causing psychological harm; this harm should ideally be avoided if the HIV diagnosis is not accurate. There can be a temptation, when presented with a positive or reactive screening test that is known to come from an instrument or assay with a very high sensitivity and specificity, to present this result as a diagnosis to the patient. However, a false diagnosis from a false-positive screen would not only be harmful, but given the low prevalence of the disease in the screened population, would happen fairly frequently; in some settings the number of false positives may actually outnumber the number of true positive test results.
Better screening assays with greater specificity (even fractions of a percentage, given that specificities are already > 99%) would help reduce the number of false positives and reduce the number of potential enticements to convey an incorrect diagnosis. Therefore, by adding an additional layer of safety through greater specificity, the fourth-generation assay implementation helped improve the diagnostic safety of the laboratory and reduced the significant error risk to the clinician who would ultimately bear responsibility for conveying the HIV diagnoses to the patient. Given the increased prevalence of psychological and physical ailments in veterans, it may be even more important to ensure the diagnosis is correct to avoid increased psychological harm.27,28