Title

Power analysis of PEPFAR's recency surveillance strategy: practical limitations of hotspot identification

Presenter

Brian Honermann

Authors

B. Honermann¹, J. Sherwood¹, E. Lankiewicz¹, G. Millett¹

Institutions

¹amfAR, Public Policy, Washington, United States

BACKGROUND: Since 2019, PEPFAR introduced routine recency testing to identify hotspots of new and on-going HIV transmissions geographically, by age cohort, and among key population groups. Four years into programmatic implementation, coverage remains limited in many countries and questions have been raised about the utility and practicality of the program.
METHODS: We conducted a power analysis to determine minimum sample sizes required to reliably identify differences in geographic or population-based sub-samples from a baseline recency rate. We follow a standard power analysis in four stages to identify sample sizes required to detect recency rate increases of 25% to 200% of baseline at a power level of 90% and varying p-values of .05-.2. Stage 1 is an unadjusted power analysis. Stage 2 adjusts for RITA reclassification rates of recency assays. Stages 3 and 4 adjust for recency assay sensitivity and RITA specificity using Rogan Gladen estimator methodology.
RESULTS:

Baseline recency and reclassification rates were set at 7.28% and 41% respectively based on data from Eswatini. RTRI sensitivity was assessed at 50% and RITA specificity at 95%. Sample sizes required are the number of individuals testing HIV positive in the sub-population being assessed in a given period. Results for final stage 4 analysis are shown in table 1.

Table 1: Sub-Population/Geographic Sample Sizes Required of New HIV Diagnoses to Detect Recency Rate Increases (adjusted)

	Stage 4 – Reclassification = 41%; Sensitivity = 50% Specificity = 95%	25%	50%	75%	100%	125%	150%	175%	200%
P-value	.05	14,999	4,625	2,056	1,157	740	514	378	290
	.10	15,077	3,770	1,676	943	604	419	308	236
	.15	13,036	3,259	1,449	815	522	363	267	204
	.20	11,566	2,892	1,286	723	463	322	237	181

CONCLUSIONS:

Based on current recency biomarkers and assays, the sample sizes required to reliably detect hotspots of new HIV transmissions at small geographic or subpopulation levels requires high numbers of people testing positive. In FY2022 PEPFAR data, the median district level geographic region diagnosed only 436 new individuals all year and 108 per quarter - far below the sample sizes required to consistently identify even moderate hotspots at the district level, let alone at a smaller geographic level or facility level. PEPFAR should reassess this strategy given practical limitations of existing recency assays.

Download the e-Poster (PDF)