3.5.3 Oexle et al. (A-7) calculated the negative predictive value of a test for carriers of X-linked ornithine transcarbamylase deficiency (OTCD-a disorder of the urea cycle). A test known as the "allopurinol test" is often used as a screening device of potential carriers whose rel- atives are OTCD patients. They cited a study by Brusilow and Horwich (A-8) that estimated the sensitivity of the allopurinol test as .927. Ocxle et al. themselves estimated the speci- ficity of the allopurinol test as .997. Also they estimated the prevalence in the population of individuals with OTCD as 1/32000. Use this information and Bayes's theorem to calcu- late the predictive value negative of the allopurinol screening test.