Figure 1: The summary for test procedure and interpretation of test results. (a) Negative result: only one coloured band appears in the control window “C.” (b) Positive result: in addition to the control band, another red to deep purple coloured band appears in the test window “T.” (c) Invalid result: the test should be considered invalid if no bands appear on the device. The test should also be considered invalid if only test band appears and no control band appears. Repeat the test with a new device ensuring that the test procedure has been followed accurately.