Interestingly, the prevalence from LCA was quite close to that obtained by using the standard cut-point analysis.
Firstly we used the standard cut point for 'harmful' alcohol use (total score 16+) to derive a binary outcome.
Figure 2 shows the number of respondents with PTSD during the first and second waves, using the standard cut-off point of ≥ 2.5 (see Methods).
To assess reliability, internal consistency was evaluated by calculating the Cronbach's α statistic using the standard cut off point of 0.7 [ 17].
Similarly, for the CPSS and for the SCARED-41, using the standard cut-off points as established in American children would have given significant overestimations of children with mental disorder.
At the AHI cut-point of ≥15, STOP-BANG had sensitivity and NPV of 100%, and since this is the standard cut-point conventionally used to determine need for CPAP, 28 we suggest that the STOP-BANG Questionnaire is the preferred tool for prediction of SDB in the sleep clinic setting of those currently available.
If we had used the standard cut-off score of 15 for the DSRS as established for British children, the utility of the scale would have deteriorated considerably (PPV 0.54 and NPV 0.92 for optimum cut-off point in this research and PPV 0.32 and NPV 0.93 for the standard cut-off point) [ 41].
Due to the small sample size of the low and high NPI groups, we did not use the standard NPI cut-points of 3.4 and 5.4, but binarized the population at the midpoint of this NPI range (4.4).
Figure 3 and Figure 4 presents odds ratios for laboratory values dichotomized using standard cut-points.
Continuous variables, not linearly related to the outcome, were categorized using the quartiles as cut-points, or by using biologically important, or recommended cut-points.
