Urine Toxicology in Adults Evaluated for a Central Hypersomnia and How the Results Modify the Physician's Diagnosis.

Drugs and psychoactive substances can cause sleepiness and when undetected, may lead to over diagnosis of central hypersomnias. We performed urine drug testing using gas chromatography-mass spectrometry in adults undergoing multiple sleep latency testing (MSLT) for a suspected central hypersomnia. We examined how the drug test results modified the treating physician's diagnosis.

One hundred eighty-six consecutive patients with a suspected central hypersomnia who underwent clinical assessment, MSLT and urine drug testing by gas chromatography-mass spectrometry were retrospectively studied. Physicians made a diagnosis after clinical assessment and MSLT and were initially blinded to the urine drug test results.

A third of patients assessed for subjective hypersomnia had a positive urine drug test for a substance affecting sleep. Opioids, cannabis, and amphetamines were the commonest drugs detected. Using MSLT, 35 (18.8%) of 186 patients had objective hypersomnia that may have been due to a drug or substance. Drugs or substances may have confounded the MSLT in 11 (20.1%) of 53 patients who fulfilled diagnostic criteria for idiopathic hypersomnia, and 12 (52%) of 23 of those who fulfilled diagnostic criteria for narcolepsy without cataplexy. Of the 75 positive urine drug samples, 61 (81%) were substances or medications not revealed in the physician interview. The treating physician had not suspected drugs or substances as a possible cause of objective hypersomnia in 34 (97%) of the 35 patients.

Drugs and psychoactive substances can confound the results of the MSLT and when undetected could lead to over diagnosis of central hypersomnias.