Briefing: A Practical Trigger for pfhrp2/3 Deletion Surveys

Programs relying on HRP2-based malaria rapid tests do not need to wait for a published prevalence estimate to know they have a problem. The field signal is observable in routine practice: a pattern of patients who test negative by RDT but positive by microscopy or molecular methods, in the absence of another obvious explanation.

From signal to survey

WHO guidance frames roughly a 5% prevalence of deletion-driven false negatives among symptomatic cases as the point at which a program should reconsider its diagnostic strategy. Reaching that conclusion responsibly requires a deletion survey—but the survey should be triggered by the discordance pattern, not commissioned at random.

The practical recommendation for district-level programs is to make discordant results reportable: when a clinician finds repeated RDT-negative, microscopy-positive malaria, that observation should flow upward as a surveillance signal in its own right. It is the cheapest possible early warning that an HRP2-only test may be losing its grip on the local parasite population—and the cue to pre-qualify an LDH-based or combination test before a switch becomes urgent.