Prediction of the final MSLT result from the results of the first three naps

OBJECTIVES: To determine if the mean sleep latency (mSL) and the presence of significant sleep onset rapid eye movement periods (SOREMPs) can be predicted from the results of the first three naps in selected patients undergoing multiple sleep latency test (MSLT). METHODS: Retrospective analysis of a number of MSLTs to identify the tests in which the mSL category and the presence of > or =2 naps with SOREMPS can be accurately predicted from the sleep latencies (SLs) of and SOREMPs in the first three naps. RESULTS: The study included 588 consecutive MSLTs performed on 552 patients during a 3-year period. (1) The mSL was normal (> or =10 min) for all MSLTs (n=90, 15%) if either (a) the SL was normal in each of the first three naps, or (b) SL was 20 min for any two of the first three naps. (2) The mSL was low (<5 min) or borderline (> or =5 and <10 min) for 99% MSLTs with SL in the low or borderline categories, respectively. (3) The accuracy of predicting > or =2 naps with SOREMPs was 100% (normal SL), 96% (borderline SL), and 89% (low SL). (4) The mSL category (normal or low) and the presence of > or =2 naps with SOREMPs were predicted with 100% accuracy in 23% of all MSLTs. CONCLUSIONS: The category of mSL can be predicted with >99% accuracy, if SL is normal, borderline, or low in each of the first three naps, or if the patient does not sleep in any two of the first three naps. MSLT can probably be shortened to three naps in up to 23% to reduce time, labor, discomfort, and cost of the test.