The field study was performed in Lofa County in northwestern Liberia. The study villages were endemic for lymphatic filariasis, onchocerciasis, schistosomiasis, and soil-transmitted helminth infections. A single round of community-directed ivermectin (MDA) had been distributed for onchocerciasis control in the study area in November of 2011, approximately 5 months before this study. Capillary blood was collected during the day by finger prick with a disposable contact-activated lancet (Becton Dickinson, Franklin Lakes, NJ). The blood was collected directly into a small 75-μL blood collection pipette for the Alere Filariasis Test Strip and a 100-μL capillary tube supplied with the BinaxNOW Filariasis card test. All testing was performed in the study villages immediately after blood was collected. For the card test, 100 μL blood were placed on the sample application pad, the card was closed, and the test result was assessed at 10 minutes. For the test strip, 75 μL blood were added to the sample application pad, and the test result was assessed at 10 minutes. Both types of test were independently read and scored by two readers. If the two readers' results did not agree, a final decision regarding the test result was made by a third reader. Cards and test strips were also read at 30 minutes and approximately 24 hours after adding blood to the tests. Test scores were recorded as follows: 0 = no test line visible (a negative test); 1+, the test line is present but weaker than the control line; 2+, the test line is equal to the control line; 3+, the test line is stronger than the control line. Tests with no control line were considered to have invalid results. A majority of subjects enrolled in the study was also tested for Mf by microscopic examination of stained thick blood films (60 μL) prepared with finger-prick blood collected between 9 pm and 12 am.