Quantifying previous SARS-CoV-2 infection through mixture modelling of antibody levels.

As countries decide on vaccination strategies and how to ease movement restrictions, estimating the proportion of the population previously infected with SARS-CoV-2 is important for predicting the future burden of COVID-19. This proportion is usually estimated from serosurvey data in two steps: first the proportion above a threshold antibody level is calculated, then the crude estimate is adjusted using external estimates of sensitivity and specificity. A drawback of this approach is that the PCR-confirmed cases used to estimate the sensitivity of the threshold may not be representative of cases in the wider population-e.g., they may be more recently infected and more severely symptomatic. Mixture modelling offers an alternative approach that does not require external data from PCR-confirmed cases. Here we illustrate the bias in the standard threshold-based approach by comparing both approaches using data from several Kenyan serosurveys. We show that the mixture model analysis produces estimates of previous infection that are often substantially higher than the standard threshold analysis.

Menstruation requirements as a barrier to contraceptive access in Kenya.

BACKGROUND: In many countries, non-menstruating women are routinely denied contraceptive services even when pregnancy can easily be ruled out. OBJECTIVE: To determine whether menstruation requirements in Kenya constitute a barrier to access for potential family planning clients. DESIGN: Prospective and retrospective observational study. SETTING: Nine family planning clinics in western Kenya. SUBJECTS: Women presenting as new clients at Ministry of Health family planning clinics. INTERVENTIONS: Researchers used prospective tracking and retrospective record reviews to compare the menstrual status of women presenting for family planning services with that of women who received methods in family planning clinics. MAIN OUTCOME MEASURES: Dichotomous outcomes (menstruating versus non-menstruating women). RESULTS: During the eight-week period that tally sheets were used in the one hospital and eight health centres, 45% of the 760 women presenting for services as new clients were not menstruating (clinic range = 19%-70%). In contrast, information from clinic registers and client records in the same nine clinics showed that the (weighted) proportion of registered new clients who were menstruating was 85% (n = 102). We estimated that 78% of non-menstruating women (35% of all potential new clients) were sent away without services. CONCLUSION: For most women turned away, it is likely that pregnancy could be ruled out easily with a history and an examination. Menstruation as a pre-condition for provision of contraception wastes valuable resources and denies women their right to contraception.

Antifolate drug resistance and point mutations in Plasmodium falciparum in Kenya.

Due to increased chloroquine resistance, the antifolate/sulpha drug combinations are becoming increasingly important in the chemotherapy of falciparum malaria. However, point mutations in the dihydrofolate reductase gene lead to resistance to the antifolate drugs. We therefore investigated the prevalence of the 6 reported point mutations in this gene among field isolates of Plasmodium falciparum from Kenya, to determine if the mutations correlated with resistance to pyrimethamine and the biguanides cycloguanil and chlorcycloguanil. We used a mutation-specific polymerase chain reaction technique to test for these reported mutations in 21 Kenyan isolates and 4 reference lines. We also amplified and directly sequenced the dihydrofolate reductase coding sequence from these parasites to confirm the results and test for other possible mutations. Of the reported mutations, we found S108N, which is the central mutation of pyrimethamine resistance, and mutations N51I and C59R, which modulate the levels of resistance and may confer decreases in response to cycloguanil that are folate and p-aminobenzoic acid dependent. No isolate possessed the paired point mutations S108T and A16V, or I164L and S108N, which have been associated with cycloguanil resistance in previous studies. These results provided supportive evidence for the combined use of a cycloguanil-class drug (e.g., chlorproguanil) and a sulpha drug (e.g., dapsone) against P.falciparum malaria in Kenya.