Background: Obstructive sleep apnoea (OSA) is typically diagnosed with single-night sleep studies, yet night-to-night variability may lead to diagnostic misclassification and affect treatment decisions. The clinical role of multi-night testing remains uncertain.
Study design and methods: We conducted a two-round modified Delphi study involving 13 international sleep medicine experts to explore consensus on indications, timing, conduction, and interpretation of multi-night testing. Structured questionnaires and anonymised feedback were employed across rounds. Consensus was defined as ≥70 % agreement.
Results: Consensus was achieved on 12 of 17 statements (71 %). Experts supported multi-night testing in cases of suspected night-to-night-variability in OSA, borderline apnoea-hypopnoea index (AHI), or when clinical impressions are incongruent with test results. A three-night protocol was considered a practical balance between diagnostic yield and feasibility. The mean AHI across valid nights was endorsed to guide treatment decisions. Experts also supported limiting the interval between test nights to one month to minimise physiological confounders. No consensus was reached regarding the suitability of simplified tools (e.g. oximetry) are appropriate for extended monitoring, and uncertainty remains about how best to integrate multi-night data into clinical decision-making.
Interpretation: Expert opinion supports selective multi-night testing in diagnostically uncertain OSA cases. A three-night protocol and mean AHI-based treatment recommendation thresholds were endorsed. These findings highlight the limitations of single-night assessments and identify priority areas for future research and standardisation before broad implementation into clinical practice.
Keywords: Apnoea-hypopnoea index; Delphi consensus; Multi-night testing; Obstructive sleep apnoea.
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