Assessing the utility of pregnant women as a sentinel surveillance population for malaria in Geita, Tanzania, 2019 - 2021

Abstract

Objectives: Estimates of malaria burden and intervention uptake in Africa are primarily based on household surveys. However, their expense and infrequency limit their utility. We investigated whether data collected during antenatal care (ANC) can provide relevant information for decision-makers.

Methods: Malaria test positivity rates and questionnaire data from ANC attendees at 39 health facilities were compared to questionnaire data and positivity rates among children from two cross-sectional surveys in the facilities' corresponding catchment areas.

Results: Trends in parasitemia among ANC attendees were predictive of trends in parasitemia among children at the council level (mean absolute error 6.0%). Primigravid ANC attendees had the lowest rates of net ownership (modeled odds ratio [OR] 0.28, 95% CI 0.19-0.40) and use (OR 0.58, 95% CI 0.42-0.79). ANC attendees reported higher levels of care-seeking (OR 1.78, 95% CI 1.48-2.14), malaria testing (OR 4.16, 95% CI 3.44-5.04), and treatment for children with fever (OR 7.66, 95% CI 4.89-11.98) compared to women surveyed in households, raising concerns about social desirability bias disproportionately impacting ANC surveys.

Conclusion: ANC surveillance is an effective strategy for tracking trends in malaria burden. More work is required to elucidate the value of administering questionnaires to ANC attendees.

Keywords: Antenatal care; Malaria; Surveillance; Tanzania.

Fig. 1.

TPR of ANC1 attendees (blue), outpatient health facility attendees under 5 years of age (green), and at cross-sectional household surveys (black) by council. (Lines and 95% CI bands represent unadjusted LOESS regression). ANC1, first antenatal care; TPR, test positivity rate.

Fig. 2.

Fitted models of TPR among children under 5 at cross-sectional household surveys vs ANC1 attendees at baseline (top) and endline (bottom) surveys by ANC attendee age category. Health facility level data with 95% credible intervals are shown in the background; data aggregated to council level are shown in the foreground. ANC1, first antenatal care; TPR, test positivity rate.

Fig. 3.

Change in the mean log odds of parasitemia between baseline and endline surveys among first ANC attendees and children under 5 in the household surveys, paired by council. Odds represent the modeled change with a random effect on health facility. ANC, antenatal care.