Figure 3. Accuracy of the paper-based newborn SCD screening test.

(a) Representative bloodstains produced on paper by HbS-positive and HbS-negative newborn samples. (b) Confusion matrix of the results of tests performed and interpreted by local health workers at the newborn screening laboratory of the Clinica de Celulas Falciformes at the Dispensario Materno Infantil (Cabinda, Angola). Shaded cells contain numbers of correctly screened newborns (i.e. true HbS-positives and true HbS-negatives).