Objectivating nasality in healthy and velopharyngeal insufficient children with the Nasalance Acquisition System (NasalView). Defining minimal required speech tasks assessing normative values for Dutch language.

Objectives: (1) To define normative nasalance data for Dutch language with "the NasalView System", and obtain a reference for normality when nasality is evaluated in children. (2) To investigate the minimal number of required speech tasks for a reliable nasalance measurement.
Methods: 55 children (30 normal and 25 velopharyngeal insufficient), aged between 4 and 11 were included. All children had to read or repeat two Dutch passages ((one with a normal amount of nasal consonants (normal passage) and one with none (nonnasal passage)). Further, one normal and one velopharyngeal insufficient subject read a passage in repetition to test the NasalViews reproducibility: (1) For both passages, group means (GM) and standard deviations (S.D.) were used to compute "pathological nasalance boundaries" [GM +/- (2 x S.D.)], in combination with the coefficient of variation (CV), sensitivity, specificity and positive predictive values. (2) With ANOVA all sentences within each passage were tested for significant differences in nasalance.
Results: (1) The pathological boundaries were 28.6-41.4% (GM: 35.0) and 21.4-34.7% (GM: 28.1), for the normal and nonnasal passage, respectively. For the normal passage a sensitivity of 96%, a specificity of 93% and a positive predictive value of 92% was computed. For the nonnasal passage these parameters were 96, 95 and 96%, respectively. Intra subject CVs of 3.6% (normal subject) and 1.5% (VI subject) showed good reproducibility of measurements. (2) Within the normal passage only the third sentence was significantly different in nasalance, compared to the entire passage (31.2% versus 35.0%). Within the nonnasal passage the second and fifth sentences were significantly different (23.8 and 24.8% versus 28.1%). However, the individual nonsignificantly different sentences showed a higher variation in nasalance compared to the entire passages.
Conclusions: The NasalView System seems to be reliable and quantifies valid nasalance values when nasality is evaluated. Within both passages high levels of sensitivity, specificity and positive predictive values were obtained. The nonnasal passage discriminates slightly better for hypernasal speech. For the most reliable nasalance measurements, the entire passage should be used.