In antiglobulin tests, what may lead to false negative reactions?

In antiglobulin tests, the timing of adding anti-human globulin (AHG) is critical for the accuracy of the results. A false negative reaction can occur if there is a delayed addition of AHG after washing the cells. This delay can cause the antibodies to dissociate from the antigen-antibody complex that is formed on the red blood cells. If the AHG is not added promptly, it may not effectively bridge the antibodies attached to the cells, thus failing to demonstrate agglutination even if the antibodies were present. This leads to an underestimation of sensitized red blood cells as they may remain unaggregated.

The other options present potential issues but do not directly cause false negative reactions in the context of the antiglobulin test. For instance, contamination with bacteria could introduce variables affecting cell viability or reactions, but it does not specifically interfere with the mechanism of the antihuman globulin test. Blood specimens collected in silicon gel tubes may also affect the quality of the sample, but the main concern with antiglobulin testing is related to the timing of AHG addition, rather than the contamination of the sample. Saline stored in glass or metal containers is unlikely to impact the results of the antiglobulin test since the saline