HSAT is a convenient first test for suspected OSA, but it estimates sleep without EEG and can miss severity. Look beyond AHI to avoid under-treating.
1) AHI vs ODI—don’t stop at one number
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AHI = events/hour, but on HSAT it’s against recording time, so severity can be underestimated (e.g., insomnia, fragmented sleep).
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ODI = oxygen drops/hour (≥3–4%). A high ODI with borderline AHI signals meaningful hypoxic burden and may still merit treatment or PSG.
Rule of thumb: If ODI > AHI pattern, think “oxygen-burden phenotype”—so don’t dismiss it.
2) REM and position—simple patterns that change management
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REM-predominant clues: clusters later in the night or deeper desaturations without a position change. These events run longer and drop O₂ more.
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Positional OSA: events mainly supine. Positional therapy may help, but CPAP remains first-line for moderate–severe disease.
3) When a “mild” AHI isn’t mild
Borderline AHI (5–15) still matters if the patient has:
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Symptoms: daytime sleepiness, fatigue, snoring with witnessed apnoeas
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Comorbidities: HTN, AF, metabolic disease
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Safety-sensitive roles: drivers, heavy machinery, pilots. Consider treatment or PSG rather than “watchful waiting.”
4) Red flags → escalate to PSG/specialist
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Inadequate/inconclusive HSAT or strong clinical suspicion despite a negative study
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High T90 (e.g., >20% of recording) or frequent desat clusters with modest AHI
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Mismatch between position data and symptoms
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Complexity/comorbidities: heart failure, COPD, neuromuscular disease, opioid use, stroke, insomnia features, suspected hypoventilation
5) Quick next-step guide
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High AHI + high ODI: classic OSA → start CPAP (plus long-term risk factor management).
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High ODI, borderline AHI: oxygen-burden phenotype → treat or confirm with PSG.
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Supine clustering: positional therapy ± CPAP based on severity.
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Late-night clusters: possible REM-predominant → consider PSG if unclear.
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Borderline AHI + symptoms/comorbidities/safety risk: PSG.
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Inconclusive/poor-quality study or complex comorbidity: PSG/specialist.
How we can help: We provide streamlined HSAT with physician-interpreted reports and practical next-step guidance. When indicated, we coordinate escalation to in-lab PSG and support CPAP setup and follow-up so patients don’t fall through the cracks.
Key references:
Kapur VK, Auckley DH, Chowdhuri S, et al. Clinical Practice Guideline for Diagnostic Testing for Adult Obstructive Sleep Apnea. J Clin Sleep Med. 2017;13(3):479–504. AASM Guidelines
Royal Australian College of General Practitioners (RACGP). Obstructive sleep apnoea in adults: Clinical update. AJGP. June 2024. RACGP 2024 Guidance
Azarbarzin A, et al. The hypoxic burden of sleep apnoea predicts cardiovascular disease-related mortality. Eur Heart J. 2019;40(14):1149–1157. DOI: 10.1093/eurheartj/ehy624