Discussion
At present, although there are a number of methods used for the diagnosis and screening of OSAHS in children, they are not easy to apply or correlate poorly with PSG[15]. Therefore, it is important to find an economical, simple method of initial screening for OSAHS. This article focuses on the value of nasopharyngeal lateral radiographs for screening children with OSAHS.
Adenoid hypertrophy is a major cause of OSAHS in children. Adenoid size was assessed by imaging methods, such as nasopharyngeal lateral radiographs, CT and MRI[8,16-17]. In clinical practice, nasopharyngeal lateral radiographs are easily accepted by children and their parents for their effectiveness, tolerability and cost and are commonly used in clinical practice. Since 1979, Fuiioka first described A/N as an objective indicator of hypertrophy. Clinically, an A/N ratio ≥0.71 was considered indicative of pathological enlargement of the adenoids[13,14]. Most studies have used the A/N ratio to assess adenoid size and analyse their diagnostic value for OSAHS in children. Selvadurai S et al[18] showed that adenoid hypertrophy was larger in children with OSAHS than in those without OSAHS.Jain et al[19] showed that the size of the adenoid correlated with the severity of OSAHS. Our study showed similar results. Further analysis revealed that the A/N ratio was positively correlated with OAHI (r=0.275), suggesting that the A/N ratio can reflect the severity of OSAHS to a certain extent; however, this correlation remains weak. The reason may be that A/N can be used as an objective indicator of the size with adenoid; it only shows the anterior and posterior diameter of the adenoid; however, it does not reflect the size of the left and right diameter of the adenoid. Additionally, other factors can also cause increased upper airway resistance, such as severe allergic rhinitis and sinusitis. Obesity and overweight can also cause OSAHS in children[20-22]. Interestingly, in the A/N≥0.80 group, the A/N ratio was negatively correlated with OAHI (r=-0.208), which may explain why children with adenoidhytrophy often present with mouth breathing to relieve upper airway obstruction[23].
The pathophysiological changes of OSAHS are hypoxemia and hypercapnia, especially in children[24]. The A/N ratio can be used to evaluate not only the severity of OSAHS but also the degree of hypoxia in patients. Brook et al.[7] suggested that the degree of adenoidal hypertrophy is correlated with LSaO2. This study showed that the A/N ratio was positively correlated with the ODI (r=0.227) and negatively correlated with LSaO2 (r=-0.225). This is consistent with the abovementioned study, but the correlations were weak, likely because children with mouth breathing relieved upper airway obstruction due to adenoid hypertrophy and because the duration of apnoea in children was relatively shorter than that in adults. Furthermore, the weak correlation may be related to the morphology of adenoids.
The optimal cut-off value for the A/N ratio was 0.825 for predicting OSAHS. When applying the cut-off value for diagnosing OSAHS, the sensitivity was 45.1%, and the specificity was 80.9%. This indicated that an A/N ratio ≥0.825 had certain diagnostic value, and an A/N ratio ≥0.825 was identified as the main influencing factor of OSAHS. However, Xu Z et al [25]suggested that lateral nasopharyngeal radiographs can be screened for OSAHS in children. The method is simple and economical and has a high application value for primary hospitals and popularization studies of OSAHS.