## 4 Discussion  
The combined use of systematic reviews and meta-analyses is increasingly adopted in the field of diagnostic test accuracy. This approach has the advantage of deriving more generalizable summary estimates of the diagnostic accuracy of an index test by combining data from multiple primary studies, which should provide a more robust foundation for guidelines, recommendation, and clinical decision-making. An additional advantage is the ability to identify areas where data are either insufficient or inconsistent, thereby guiding future research efforts to address these gaps. This process facilitates that diagnostic procedures are based on the most robust scientific evidence available. Already part of the standard PSG, oximetry is a simple, widely available, and non-invasive method of measuring blood oxygen saturation and recording blood volume changes in tissue using the photoplethysmographic signals. Three clusters of desaturation events on an overnight oximetry trend graph have been demonstrated by [PERSON] et al. [12] to yield a 97% PPV. Another study by [PERSON] et al. [48] showed that the McGill score accurately estimates the severity of OSA and can also play an important role in planning for adenotonsillectomy. The McGill score is a pediatric screening tool for OSA, based on oxygen saturation (SpO2) monitoring. It evaluates desaturation events, the desaturation index, and the time spent with SpO2 below critical thresholds. The score ranges from 1 to 4, with higher scores indicating a greater likelihood of OSA. However, these interpretations are complex, time-consuming, and may also vary regarding the exact number of clusters. Another parameter is ODI, i.e., the number of times per hour of sleep that SpO2 falls by a defined level from baseline (e.g., ODI4 indicates a \(\geq\)4% reduction in SpO2). Notably, due to the variability in definitions and cutoff values for ODI, there is currently no consensus on which the threshold is the most accurate or on the optimal definition of abnormal values in children. [PERSON] et al. [15] demonstrated that an ODI4 of \(>\)2.05 events/h exhibits strong diagnostic performance, with a sensitivity of 78% and a specificity of 89%. However, it has been observed that this threshold may overlap with ODI values observed in healthy children [49]. [PERSON] et al. [28] recommended the use of a combination of clinical symptoms (such as apnea, mouth breathing, and restlessness) along with the ODI3 as a screening tool for pediatric OSA. Moreover, the standard deviation of SpO2, representing the variability of SpO2 from the baseline, was shown to correlate strongly with the AHI, with a higher standard deviation indicating more severe OSA and a standard deviation greater than 1.06 providing strong evidence of moderate to severe OSA [44]. Conventional oximetry parameters were also recently joined with features from other data elaboration approaches in order to improve their diagnostic performance, including statistical parameters, power spectral density, and nonlinear features [11]. A previous systematic review aimed to qualitatively summarize abnormal conventional oximetry patterns that predict pediatric OSA and to identify nocturnal oximetry abnormalities predicting the response to treatment interventions for OSA and potential treatment complications [17]. The study concluded that at least three clusters of desaturation events, and a minimum of three SpO2 drops below 90% in a nocturnal oximetry recording with a minimum duration of 6 h, are indicative of moderate-to-severe OSA. Furthermore, children without clusters of desaturation events exhibit a low risk of major respiratory complications following adenotonsillectomy [17]. However, the review did not include any quantitative analyses (i.e., meta-analysis). Another systematic review tried to qualitatively investigate the diagnostic performance of portable single- or two-channel sleep monitors compared with PSG for the diagnosis of pediatric OSA [9].