GC-MS & SIFT-MS results
Seven VOCs differed significantly between recovered, mild rattling, moderate rattling and severe rattling infants (table 2). No VOCs differed significantly between ‘recovered’ and ‘mild rattling’ infants. 2D scatterplot based on ethylenimine and methenamine showed overlap between recovered and mild rattling infants (figure 1). Additional analysis of the recovered and mild rattling group versus the moderate and severe rattling group showed that eight VOCs were significantly different (table 2).
Three DMs were developed for each of the four diagnostic groups and compared in a one-vs-all approach. DM 1 included the significant VOCs, DM 2 also included PROs and DM 3 only included PROs. The same DMs were developed for the differentiation between recovered/mild rattlers and moderate/severe rattlers. ROC-AUC, accuracy, sensitivity and specificity are shown in table 3 and table 4. Results of the SIFT-MS were very similar to those of the GC-MS (supplement section 4). Accuracies of the 3 DMs based on exhaled breath ranged between 59.21-69.74%, while for the DMs based on exhaled breath and PROs they ranged between 65.79-88.16%.