To the Editor.—
Blum and colleagues1 report a strong relationship between an allele of the dopamine D2 receptor and alcoholism. After controlling for the confounding effects of race and sex (matching and statistical control), a contingency table basic to their conclusion was constructed. Of 35 nonalcoholics, the A1 allele was found to be present in seven subjects and absent in 28. Of 35 alcoholics, the A1 allele was present in 24 subjects and absent in 11. A calculated χ of 14.8 (df= 1, P<.001) demonstrated to the authors a significant association between alcoholism and the presence of the A1 allele.To further evaluate the import of the reported finding, statistical analyses were performed to determine the predictive value of the presence or absence of the A, allele for medical diagnosis. The sensitivity of the A1 allele test was calculated from the authors data to be 0.686 (24/35).
Rubin LS. Allelic Association of Human Dopamine D2 Receptor Gene in Alcoholism. JAMA. 1990;264(14):1808. doi:10.1001/jama.1990.03450140027015