Harr Immunology, Serology & Blood Bank (ISBB) Practice Test

In the context of evaluating a patient for celiac disease, if the initial tests for anti-tissue transglutaminase (tTG) and anti-gliadin antibodies come back negative, the next appropriate step is to perform HLA DQ typing. This is due to the role of HLA genes, particularly HLA-DQ2 and HLA-DQ8, in the pathogenesis of celiac disease.

The presence of these HLA types is necessary for the disease to manifest; however, their absence makes celiac disease highly unlikely. Since a significant proportion of the population carries these HLA types without having celiac disease, HLA typing serves as a useful tool in excluding the diagnosis.

IgG and IgM level tests would not specifically help in the diagnosis of celiac disease and do not have a direct role in confirming or ruling out this condition. Testing for HLA DR typing is less relevant in this context compared to HLA DQ typing, as HLA-DQ2 and HLA-DQ8 are more directly related to the risk of developing celiac disease.

Thus, ordering HLA DQ typing is the most logical and clinically relevant next step after negative serological testing for celiac disease.