Use of a computer-based postal questionnaire for the detection of hypothyroidism following radioiodine therapy for thyrotoxicosis.

A computer-processed postal questionnaire was devised to detect hypothyroidism in patients treated previously for thyrotoxicosis with radioiodine. In a study of 232 patients treated with 131I at the Royal Melbourne Hospital between four and ten years previously, the sum of symptomatic answers in the questionnaire was a sensitive discriminator of hypothyroidism, and allowed 80% of euthyroid patients to be excluded from further assessment. Questions concerned with general well-being and energy, voice and skin changes, showed the highest sensitivity and specificity. The combination of these questions alone was an effective means of identifying hypothyroidism, with a sensitivity and specificity comparable to the more sophisticated technique of discriminant function analysis. Hypothyroidism had an incidence of between 20% and 35% six to eight years after 131I therapy and was related to a smaller initial goitre size for a given dose of 131I. This postal questionnaire, in conjunction with a computer-based automatic recall system, promises to be an efficient and reliable screening tool for the detection of hypothyroidism in the increasing number of patients "at risk" following 131I therapy.