Comparison of lavage and swabs for the collection of genital ulcer specimens to measure HIV RNA shedding

Abstract

Background The optimum collection procedure for the evaluation of HIV-1 burden in ulcer secretions has not been well defined. Objectives The objective of this study was to compare ulcer swabs and ulcer lavages for the detection and quantitation of HIV-1 RNA in genital ulcers. Study design A convenience sample of the first 84 HIV-positive participants in a randomized double blind placebo controlled trial of acyclovir episodic treatment among men with genital ulcer disease were included in this evaluation. At baseline, participants were screened for HIV, syphilis and HSV-2 by serology and for ulcer etiology by PCR. Ulcer specimens were collected by using (1) a non-traumatic washing procedure with 10 ml of PBS, and (2) sterile dry swabs. Ulcer samples were tested with HIV-1 Amplicor 1.5 Ultra Sensitive Assay with a lower threshold of 50 copies/ml. Results Of ulcer samples 35 (41.7%) had HIV detected by ulcer lavage and 32 (38.1%) by swabs ( p = 0.68). Overall, 45 (53.6%) were positive by one or both methods. The overall proportion of agreement was 73% (61/84). The chance-corrected proportion of agreement was 0.46 (95% CI: 0.26, 0.65) as estimated by the Kappa statistic. The log mean viral load from lavages (1.49 log 10 copies/ml, 95% CI: 1.17–1.81) did not differ significantly from that of swabs (1.41 log 10 copies/ml, 95% CI: 1.16–1.71) ( p = 0.29) with a mean difference of 0.08 log copies/ml (SD 0.96) . Conclusion Ulcer lavage and ulcer swab performed in moderate agreement in the detection and quantitation of HIV RNA from ulcer specimens.