Relationships between test positivity rate, total laboratory confirmed cases of malaria, and malaria incidence in high burden settings of Uganda: An ecological analysis

Abstract

Background: Malaria surveillance is critical for monitoring changes in malaria morbidity over time. National Malaria Control Programs often rely on surrogate measures of malaria incidence, including the test positivity rate (TPR) and total laboratory confirmed cases of malaria (TCM), to monitor trends in malaria morbidity. However, there are limited data on the accuracy of TPR and TCM for predicting temporal changes in malaria incidence, especially in high burden settings.Methods: This study leveraged data from 5 malaria reference centers (MRCs) located in high burden settings over a 15-month period from November 2018 through January 2020 as part of an enhanced health facility-based surveillance system established in Uganda. Individual level data were collected from all outpatients including demographics, laboratory test results, and village of residence. Estimates of malaria incidence were derived from catchment areas around the MRCs. Temporal relationships between monthly aggregate measures of TPR and TCM relative to estimates of malaria incidence were examined using linear and exponential regression models.Results: A total of 149,739 outpatient visits to the 5 MRCs were recorded. Overall, malaria was suspected in 73.4% of visits, 99.1% of patients with suspected malaria received a diagnostic test, and 69.7% of those tested for malaria were positive. Temporal correlations between monthly measures of TPR and malaria incidence using linear and exponential regression models were relatively poor, with small changes in TPR frequently associated with large changes in malaria incidence. Linear regression models of temporal changes in TCM provided the most parsimonious and accurate predictor of changes in malaria incidence, with adjusted R2 values ranging from 0.81 to 0.98 across the 5 MRCs. However, the slope of the regression lines indicating the change in malaria incidence per unit change in TCM varied from 0.57 to 2.13 across the 5 MRCs, and when combining data across all 5 sites, the R2 value reduced to 0.38.Conclusions: In high malaria burden areas of Uganda, site-specific temporal changes in TCM had a strong linear relationship with malaria incidence and were a more useful metric than TPR. However, caution should be taken when comparing changes in TCM across sites.

Gender difference in the incidence of malaria diagnosed at public health facilities in Uganda

“…As expected, the incidence of malaria diagnosed at the MRCs decreased with increasing age. The magnitude of the association between female gender and malaria incidence was higher among those 15 3).…”

“…At each MRC, individual-level data from standardized HMIS registers for all patients presenting to the outpatient departments are entered into an Access database by on-site data officers. These data have been described elsewhere [15] and briefly includes village of residence, age, gender, whether malaria was suspected, whether a malaria diagnostic test was done, the type of diagnostic test done (rapid diagnostic test (RDT) or microscopy), and the result of the diagnostic test (positive or negative). UMSP supports the sites with training, supervision, and buffer stock of laboratory supplies/consumables.…”

Impact of different mosquito collection methods on indicators of Anopheles malaria vectors in Uganda

“…funestus mosquito density have been observed in Tororo district (unpublished data). Busia is also a site of very high malaria transmission [41,42], but unlike Tororo, Busia has received LLINs only (without IRS) for vector control. Malaria transmission patterns in Busia are stable and characteristic of a high transmission area [37,41].…”

East Africa International Center of Excellence for Malaria Research: Impact on Malaria Policy in Uganda

“…The proportion of patients with a negative malaria test result prescribed an antimalarial is consistently less than 5%. 7,16,[46][47][48] In 2019, UMSP supplied reusable malaria normal channel and ACT stock monitoring charts to 70 MRCs. HIAs and facility in-charges were trained to plot and update these charts weekly, use them to monitor trends in malaria cases, identify any upsurges in malaria cases, monitor ACT stock status, and regularly provide updates to the district leadership and NMCD.…”