Figure 4. Possible results for the three-line SD Bioline HIV rapid diagnostic test (RDT) that presents indicator lines for control, HIV-2 and HIV-1.

HIV-1/2 positive (A), HIV-1 positive results (B, F & G), HIV-2 positive (C), HIV negative (D) and Invalid (E) results. A-E were considered "obvious" because the manufacturers' instruction illustrated these types of result. F & G are both HIV-1 positive and considered "difficult" because the correct interpretation required comparison of intensities for the middle and bottom lines (F), or the ability to see and interpret a faint line (top line, G).