In a patient with a home sleep test showing an Apnea‑Hypopnea Index of 2.5 (normal) who continues to experience fatigue and non‑restorative sleep, what further diagnostic evaluation and management steps are recommended?

Further Evaluation for Persistent Fatigue with Normal Home Sleep Test

Proceed directly to in-laboratory polysomnography (PSG) because a negative or low-AHI home sleep test cannot rule out sleep-disordered breathing or other sleep disorders causing your patient's symptoms. 1

Why the Home Sleep Test is Insufficient

Technical Limitations of Home Sleep Testing

• Home sleep apnea tests systematically underestimate OSA severity by 10-26% compared to in-laboratory PSG because they calculate events per hour of recording time rather than actual sleep time. 2

• HSATs lack EEG, EOG, and EMG sensors, which means they cannot detect respiratory effort-related arousals (RERAs) that fragment sleep without causing full apneas or hypopneas. 1, 2

• The inability to measure sleep stages means HSATs miss hypopneas terminated only by cortical arousals rather than oxygen desaturations, leading to false-negative results particularly in mild-to-moderate OSA. 1, 2

• Night-to-night variability in OSA severity is substantial, and a single home test may have captured an atypically good night. 3

Guideline-Mandated Next Step

• The American Academy of Sleep Medicine explicitly recommends that if a single HSAT is negative, inconclusive, or shows low AHI but clinical suspicion remains, polysomnography must be performed. 1, 4

• This is a STRONG recommendation based on the high false-negative rate of HSATs and their inability to detect arousal-based respiratory events. 1, 4

What In-Laboratory PSG Will Evaluate

Sleep Architecture and Fragmentation

• PSG will quantify sleep efficiency, sleep stage distribution, and arousal index to determine if sleep fragmentation from non-apneic causes is present. 1, 5

• The arousal index is critical because patients can have significant sleep disruption from RERAs (RDI elevated but AHI normal) that HSATs cannot detect. 5

Alternative Sleep Disorders

• PSG can diagnose periodic limb movement disorder, which causes non-restorative sleep and would be completely missed on HSAT. 1

• Central sleep apnea patterns, sleep-related hypoventilation, and other breathing disorders require EEG-based sleep staging for accurate diagnosis. 1

• Paradoxical insomnia (sleep state misperception) can only be identified when objective sleep time is measured against subjective complaints. 1

Position-Dependent and REM-Related Events

• PSG will identify if respiratory events are concentrated in REM sleep or specific body positions, which may result in a misleadingly low overall AHI on HSAT but still cause significant symptoms. 3

Additional Diagnostic Considerations

Comprehensive Sleep Evaluation Components

• Evaluate for restless legs syndrome symptoms (uncomfortable sensations in legs at rest, urge to move, worse in evening, relieved by movement) which would not appear on any sleep study but causes non-restorative sleep. 1

• Screen for circadian rhythm disorders by assessing sleep-wake timing preferences, work schedule, and whether symptoms improve on weekends or vacation. 1

• Assess for sleep-related movement disorders beyond what HSAT can capture, including bruxism and rhythmic movement disorder. 1

Medical and Psychiatric Comorbidities

• Evaluate thyroid function, iron studies (ferritin), and vitamin D levels as deficiencies commonly cause fatigue mimicking or coexisting with sleep disorders. 1

• Screen for depression and anxiety using validated instruments, as these frequently present with fatigue and non-restorative sleep independent of sleep-disordered breathing. 1

• Review medications for sedating or alertness-impairing effects, including antihistamines, beta-blockers, and benzodiazepines. 1

Common Pitfalls to Avoid

• Do not rely on the AHI cutoff of 5 as the sole determinant of clinical significance. Patients with AHI 2-5 plus significant RERAs may have clinically important sleep-disordered breathing. 6

• Do not assume normal oximetry rules out sleep-disordered breathing. Many patients with significant sleep fragmentation from RERAs maintain normal oxygen saturation. 1

• Do not order a repeat HSAT as this will likely yield similar results and further delay definitive diagnosis; proceed directly to PSG. 1, 4

• Do not dismiss symptoms as "just stress" or "just depression" without objective sleep evaluation, as untreated sleep disorders worsen quality of life and increase cardiovascular risk. 1