Spot test for detection of sickling hemoglobin.

We describe a simple, noninstrumental procedure for detecting hemoglobin S in samples of blood on filter paper, with use of small volumes of reagents. The method depends on the differential solubilities of reduced sickling and nonsickling hemoglobin in phosphate solutions (1, 2) or Sickledex reagent’ and the apparent solubilizing effect of urea on reduced hemoglobin S (3). The color of paired phosphate and phosphate-urea hemolysates distinguishes hemoglobin SS from AS and other hemoglobin types.