Background. Syphilis and HIV co-infection is increasingly common. In co-infected patients, syphilis can increase transmission of HIV by increasing viral shedding and seminal viral load. Point of care tests for syphilis and HIV may reduce morbidity and transmission of these infections by increasing the number of patients identified and treated. This study evaluated three research-use only, rapid diagnostic tests (RDTs) that detect HIV and Treponema pallidum (TP) antibody simultaneously, in serum.
Methods. Serum from 150 patients, including 29 TP-/ HIV-, 22 TP + /HIV-, 35 TP-/HIV+ and 64 TP + /HIV+ were tested. Reference test were the Siemens Advia Centaur HIV 1/O/2 and the Serodia TP-PA. Specimens were tested in parallel by the 3 RDTs by a technician blinded to reference results. RDTs included MedMira Multiplo HIV/TP, Standard Diagnostics (SD) BIOLINE HIV/Syphilis Duo, and ChemBio DPP® HIV-Syphilis Assay. Specimens that yielded discordant or difficult-to-interpret results were repeated by both references and all 3 RDTs. Data were evaluated by summary statistics.
Results. Sensitivity and specificity of the RDTs as compared to reference methods are in the table. Repeat testing did not resolve any false negative (FN) or false positive (FP) results. All FN TP and HIV results observed by the RDTs were from HIV + /TP+ specimens. Faint TP reactions were noted for 16 MedMira, 10 SD and 6 ChemBio tests. Faint HIV reactions were observed in 2 MedMira, 3 SD and 2 ChemBio tests. Repeat testing yielded similarly difficult to interpret results. Kappa coefficient between the three RDTs was 0.95 for the HIV component and 0.93 for TP.
Performance of 3 RDTs, as compared to reference methods.
| HIV (% (95% Confidence Interval)) | TP (% (95% Confidence Interval)) | |||
|---|---|---|---|---|
| Sensitivity | Specificity | Sensitivity | Specificity | |
| SD | 96 (89-99) | 100 (91-100) | 93 (85-97) | 100 (93-100) |
| ChemBio | 97 (91-99) | 98 (88-100) | 95 (88-98) | 100 (93-100) |
| MedMira | 96 (89-99) | 94 (83-98) | 94 (86-98) | 97 (88-99) |
Conclusion. The 3 RDTs performed comparably, with excellent sensitivity and specificity. Further evaluation of these tests, using whole blood in the clinic, will aid in the determination of their performance as point-of-care tests.
Disclosures. R. M. Humphries, Affinity Biosensors: Investigator, Research support