Multiple puncture tuberculin tests: relationship of false negative responses to variations in dried tuberculin coating.

Multiple puncture dried tuberculin tests compare favourably with the standard Mantoux test provided the tips of the metal prongs are thinly and uniformly coated with tuberculin. Unfortunately, surface tension, varying viscosity of the acacia solutions, and deeper dipping depths lead to increased quantities of tuberculin materials adhering to the metal prongs which results in thickening and retraction of the materials on the metal. Solutions of tuberculin in buffered phosphate produce thin and uniform coatings provided adequate cleaning of the metal--especially degreasing--is carried out. In the absence of this the coating layer may fragment. However, provided the distal 0.6-0.8 mm is covered, sufficient tuberculin will be deposited intradermally.