False alarm on a malaria "outbreak" linked to inconsistencies in malaria diagnostic supply: a call to strengthen supply chain management: Sierra Leone, May-July 2023.

Abstract

Background: Malaria transmission in Sierra Leone is intense and perennial, accounting for 40% of clinical consultations. Medical workers diagnose suspected malaria cases using rapid diagnostic tests (RDT) and microscopy, with facility-level results reported to the Health Management Information System (HMIS) as monthly aggregates. Commodity stocks are reported to the Logistics Management Information System (LMIS). Partners investigated a striking increase in confirmed malaria during May-July 2023 in Sierra Leone, peaking in June to 46% above the June 2018-2022 mean.

Methods: The team first analysed national, district, and facility HMIS/LMIS data for RDT stocks, testing rates, and confirmed cases during January 2018-October 2023. Epidemic thresholds, defined as case counts two standard deviations (σ) above the previous 5 years' monthly mean, were assessed. Then four facilities in two districts were visited to interview staff. Lastly, the team reanalysed LMIS RDT stock data for all facilities in Sierra Leone using R to categorize their stock status by month.

Results: National epidemic thresholds were surpassed in May (2.56σ) and June (4.81σ) 2023. Twelve of sixteen districts surpassed epidemic thresholds during May-June. Investigation revealed inconsistent RDT distribution to facilities over time. National RDT distribution spiked in May 2023, when 551,888 RDT test kits were delivered. This was substantially larger than the 2019-2022 mean for May (53,121, 1,000% increase) and all months (126,866, 435% increase). Subsequently in June 2023, 386,343 tests were performed, 36% higher than the June 2018-2022 mean (285,123). Staff at all four visited facilities reported recurrent RDT stockouts. The proportion of facilities in Sierra Leone reporting positive RDT stocks at both the start and end of the month increased from 14% in April to 74% in June. 51% of facilities began May with RDT stockout and received RDTs that month.

Conclusions: The 2023 spike in confirmed malaria was likely related to increased testing following an unusually large distribution of RDTs. Fluctuations in RDT availability impede the ability to recognize true case variations. Sierra Leone and its partners can strengthen supply chain logistics and health commodity stock tracking to ensure a consistent supply of RDTs and improve interpretation of surveillance data.