Medical Disorders Among Psychiatric Patients

To the Editor: We were pleased to see the brief report by Koran and colleagues in the December 2002 issue (1) that focused on the important topic of unrecognized medical disorders among psychiatric patients. One of the assessment tools the authors used was a medical questionnaire consisting of items with high predictive value for physical disorders: a symptoms checklist and items addressing current and past illnesses, current medications, and family history (2).

The questionnaire had a high false-negative rate (26 percent). Although a questionnaire alone cannot adequately identify physical disorders, use of a few additional queries for which positive responses would suggest a medical rather than a psychiatric diagnosis might be helpful. The addition of such items could be particularly important for patients with unrecognized medical problems whose presentation appears to be psychiatric. Historical elements suggesting that a medical problem might be more likely than a psychiatric problem include lack of a psychiatric history, extremely sudden onset of symptoms, onset of symptoms before age 12 or after age 40, decreasing cognitive abilities, and visual or tactile hallucinations (3). In some cases this information would have to be obtained from collateral sources. The mental status and physical examinations mentioned by the authors would identify other important clues, such as specific physical abnormalities or alteration of cognition.

The authors measured free thyroxine levels to screen for thyroid disease. Fourteen of 18 abnormal results were false positives. The enhanced sensitivity and specificity of thyroid-stimulating hormone (TSH) assays have greatly improved laboratory assessment of thyroid function. Because TSH levels change dynamically in response to alteration of free T4 and T3, a logical approach to thyroid testing is to determine first whether the TSH level is abnormal. With rare exceptions, a normal TSH level excludes primary abnormality of thyroid function (4).