Q: My 30 years old friend is suffering from dengue fever and thrombocytopaenia. According to him, his blood group was A negative but the blood test report showed A positive. He underwent a blood test again, which showed the same results. Is this possible?

A:Causes for false negative Rh D typing are immunoglobulins coated in vivo, weak D antigen, variant antigen and reagent deterioration. False positive Rh D typing - cold agglutinins, rouleux formation, bacterial contamination of reagent and patient has recently been transfused with Rh D cells.

That is why there is a recommendation by the drug controller to test Rh D antigen using reagent from two different companies or same company but two different batches.