Drug-induced lymphocyte stimulation test is not useful for the diagnosis of drug-induced pneumonia.

Diagnosis of drug-induced pneumonia, which represents pulmonary toxicity caused by certain drugs, is difficult, as a large number of different drugs can elicit various immune-mediated diseases with distinct pathomechanisms. The drug-induced lymphocyte stimulation test (DLST) is widely used for diagnosing drug-induced pneumonia in Japan. Recent reports, however, indicate that DLST is not reliable for diagnosis of drug-induced pneumonia. To diagnose drug-induced pneumonia, a provocation test with the suspected drug is the most reliable method of assessing the relationship between the drug and pneumonia. We examined the correlation between the DLST and the provocation test in 6 cases of suspected drug-induced pneumonia. DLST was performed in all of the patients. The causes of pneumonia in all patients were confirmed by a provocation test. The DLST was positive in 3 of 6 cases of suspected drug-induced pneumonia, but the suspected drugs were ruled out by the provocation test. If we had relied solely on the DLST, these 3 cases would have been labeled as false allergy. The results of the DLST did not coincide with the results of the provocation test in any of the cases. Our results suggest that the DLST is not useful for the diagnosis of drug-induced pneumonia. Following provocation with the causative drug, reappearance of pulmonary infiltration was not observed in any of the cases. These findings indicate that a carefully performed provocation test is the safe and most reliable method.