Risk stratification of HIV infection for patients needing molecular confirmation with the Abbott 4th generation Architect System

Background: Some patients need their 4^th generation HIV testing results confirmed with molecular testing after primary confirmatory testing which may not be immediately available. Further risk stratification of these patients pending the results of molecular testing may be of value not only for patient counseling but also for treatment of women in labor.

Objectives: To determine the risk of a positive test result on molecular testing for these patients.

Study design: The risk of a positive molecular test result for patients with a result needing molecular confirmation on a 4th generation HIV testing algorithm (Abbott Architect, Multispot/Geenius confirmatory test) was stratified based on the patient's white blood cell (WBC) count and the magnitude of Architect result Signal Cut Off ratio (S/CO).

Results: A total of 61,666 patients were tested with 658 (1.1%) positive results and 76 (0.12%) patients needing molecular confirmation. Patients with an S/CO of <5 or an S/CO of 5-100 with a WBC > 6.5 × 10 ⁹ cells/l had a significantly lower risk of a positive molecular HIV test (0/48, 0%) than patients with an S/CO 5-100 with a WBC < 6.0 s × 10 ⁹ cells/l (5/9, 56%, p < .001) or an S/CO > 100 (2/2, 100%, p < .001). Pregnant women had a significantly lower rate of positive test results (24/6924, 0.4%) than non-pregnant patients (634/54742, 1.1%, p < 0.001). All 12 cases needing molecular confirmation in pregnant women had negative NAT test results.

Conclusions: Patients who need their HIV results confirmed with molecular testing using a 4^th generation algorithm that includes the Abbott Architect System can be further stratified into low, intermediate, and high risk groups based on additional laboratory information pending the results of molecular testing. This risk stratification may be of value for patient counseling and treatment of women in labor.