One night of oximetry is not a sleep apnoea screen in Down syndrome

Design

retrospective review of outpatient screening data with receiver operating characteristic analysis, single UK centre, April 2020 to December 2024

Population

246 three-night pulse oximetry studies (150 complete) in children aged 1 to <18 years with Down syndrome

Primary outcome

proportion of studies with results both above and below published thresholds predictive of moderate-to-severe obstructive sleep apnoea

Effect

clinically significant night-to-night variability in 53% of complete studies; 87% of night-1 results above the reassurance thresholds; 60% of polygraphy studies showed apnoea

Children with Down syndrome have a high prevalence of obstructive sleep apnoea and are screened with overnight oximetry. This retrospective review at one UK centre looked at 246 three-night oximetry studies in children aged 1 to under 18 years with Down syndrome, with 150 complete, and asked how often the result changed between nights.

It changed in 53% of complete studies — the child crossed the published thresholds predictive of moderate-to-severe apnoea (3% oxygen desaturation index of 6.15 or more, delta index 0.555 or more) on some nights and not others. A single night, in other words, is a coin toss in half of these children.

The authors derived lower reassurance thresholds from the first night: below an oxygen desaturation index of 3.61 or a delta index of 0.49, the chance of an abnormal result on a later night was low, with negative predictive values of 79% and 81%. But only 13% of night-one results fell below those thresholds — so for the great majority of children, night one settles nothing. Two other numbers are worth carrying: 60% of the polygraphy studies showed apnoea, and 76% of moderate-to-severe disease was in children over six, which is older than screening programmes tend to assume.

• Do not exclude obstructive sleep apnoea in a child with Down syndrome on one normal night of oximetry unless the values are well below threshold.
• Three consecutive nights is what this centre used; where that is not possible, treat a single normal night as inconclusive rather than reassuring.
• Keep screening past age six — three-quarters of moderate-to-severe disease here was in older children.
• A negative predictive value of about 80% still means one child in five below the reassurance threshold will screen positive later.
• Symptoms and a witnessed history remain part of the assessment; oximetry is a screen, and polygraphy is the diagnostic test.

Why it matters

Half of these children get a different answer depending on which night you happen to record.

Don't overread it

This is a retrospective single-centre review with thresholds derived and tested in the same data; the reassurance cut-offs need external validation.

The statistics, in plain English

Night-to-night variability of this size means the test's sensitivity depends on how many nights you record, which is unusual and easy to miss — a screening threshold validated on one night does not mean the same thing applied to another. The reassurance thresholds were derived from the same dataset used to test them, so their negative predictive values of 79% and 81% are optimistic and need validating elsewhere. And with 150 complete studies at one centre, the subgroup figures rest on small numbers: 19 children fell below the oxygen desaturation index threshold.

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