Diagnostic value of nasal nitric oxide measured with non-velum closure techniques for children with primary ciliary dyskinesia
Nasal nitric oxide (nNO) is a reliable non-invasive screening test for primary ciliary dyskinesia (PCD), but the recommended technique, exhalation against resistance (ER), requires cooperation limiting its use in young children. Our objectives were to determine whether easier non-velum closure techniques have the ability to discriminate PCD and longitudinal reproducibility. We conducted a case-control study evaluating 5 breathing techniques (ER, breath hold, tidal breathing mouth open, tidal breathing mouth closed, and humming) for measuring nNO in patients with PCD compared with control subjects (cystic fibrosis [CF], non-PCD non-CF bronchiectasis, and healthy). A subgroup repeated measurements 1 month later. Sensitivity, specificity, and intraclass correlation coefficient of each nNO technique were determined. We tested 85 children (20 PCD, 32 CF, 14 broncheoctasis, and 19 healthy), aged 5 to 18 years (mean age, 11.5 years); 52% of children were male. All breathing techniques discriminated patients with PCD from control subjects with high specificity (>90%), 100% sensitivity, and intraclass correlation coefficient >0.8. nNO output cutoff values for diagnosing PCD varied with techniques (ER, 59 nL/min; breath hold, 61 nL/min; tidal breathing mouth open, 37 nL/min; tidal breathing mouth closed, 30 nL/min; humming, 41 nL/min). Non-velum closure techniques are reproducible and valid to discriminate PCD; however, they generally yield lower values than ER.