An explanation and the clinical significance of the failure of microcolumn tests to detect weak ABO and other antibodies.

Shear forces are proposed to explain the failure of antiglobulin and 'neutral' (no antiglobulin) microcolumn tests at 37 degrees C to detect weak ABO incompatibilities and other weak antibodies, clearly detectable by spin-tube methods. These shear forces can be minimized in a microcolumn test using a biphasic centrifugation phase. Although this biphasic test is not suitable for routine use, it may be of use as an investigational method for reference laboratories. This failure of microcolumn test to detect weak ABO incompatibilities is of little clinical significance as the antibodies are dubiously active at 37 degrees C.