Objective:

The objective was to establish the evidence base for diagnosing sleep apnea (SA) in adult patients using systematic review methods. Tests covered were sleep monitoring devices, radiologic imaging, laboratory assays, and clinical signs and symptoms posited for use in screening or diagnosing SA. The standard sleep lab polysomnogram (PSG) was the gold standard.

Search strategy:

Literature published from 1980 through November 1, 1997 (cutoff) was searched using Medline and Current Contents, supplemented by a manual review of the bibliographies of all accepted papers.

Selection criteria:

Studies of at least 10 adult patients suspected of or diagnosed with SA had to report the results of any test to establish or support a diagnosis of SA, relative to a standard PSG-derived apnea index (AI, the number of apneic episodes/Hour sleep); apnea-hypopnea index (AHI, the total apneas plus hypopneas during total time asleep, divided by the number of hours asleep); or respiratory distress index (RDI). Eligible languages were English, German, French, Spanish, or Italian. Diagnostic papers reporting prevalence or clinical comorbidities of SA were also accepted.

Data collection and analysis:

Based on scores for study characteristics (e.g., random order test, blinding of test readers, and use of PSG comparison), 147 studies met or exceeded the minimum evidence score. From these, data on study, patient, and test characteristics and on results were collected. Nondiagnostic studies reporting prevalence or clinical comorbidities were separately extracted.

Study and patient-level covariates were summarized and the results were analyzed using fixed effects models. Results were evaluated using summary receiver operating characteristic (ROC) curves where data were available.

Main results:

In 71 analyzable diagnostic or screening studies (7,572 patients), the sensitivity and specificity of partial channel and partial time PSGs appeared most promising as possible prescreening tests or replacements for full PSG. Prediction models achieved good sensitivity and specificity. Studies of portable devices were variable due to study and device heterogeneity. Radiologic studies and several miscellaneous studies of questionnaires, anthropomorphic signs, and ears/nose/throat (ENT) exams could not be analyzed due to insufficient data. Global clinical impressions and oximetry provided moderate sensitivity and specificity. Least accurate were flow volume loops. The review and analysis were limited by variability in PSG definitions of apnea and hypopnea, and thresholds for SA diagnosis. For sensitivity and specificity determinations, the lowest AI/AHI threshold for SA diagnosis was used. Necessary components of "standard" PSG were not consistent.

SA prevalence studies in different patient populations were reviewed. Few such studies utilized gold standard PSG to diagnose SA; so the diagnosis was based on unvalidated tests. Such prevalence estimates are suspect.

Conclusions:

The best available evidence from literature sources suggests the diagnosis of SA is still best accomplished with full PSG. Progress has been made in establishing reasonable sensitivity and specificity of tests other than full PSG, and future researchers should focus on building this evidence base. Standardization of terms and diagnostic criteria is an absolute requirement to expedite development and enhance the utility of this literature in the future.