3.1 | Study selection
A systematic literature search was conducted, resulting in a total of 4,600 records. After excluding 4,497 citations based on title and abstract, 103 full-text publications were selected for a secondary review. Ultimately, nine studies that were relevant to the diagnostic accuracy of sIgE to milk components for milk allergy were included [30-38]. The selection process is illustrated in Figure 1.
3.2 | Characteristics of included studies
Table 1 presents a summary of the main characteristics of the nine studies included in this analysis. A total of 958 participants were recruited across these studies, with five of them [31, 32, 34, 36, 37] conducted in Europe, two in South America [33, 35], and two in Asia[30, 38]. Of the nine studies, five were prospective [30, 31, 34, 35, 38], two were retrospective [33, 37], and two were case-control designs [32, 36]. Our literature search did not impose any age restrictions, but none of the studies on adults met the inclusion criteria. Therefore, all the included studies were conducted on children, with participants aged between 2 months and 16.7 years. At least one milk allergy component was used in the diagnostic accuracy analysis of CRD across all the included studies. Three of the studies used a blinded approach [30, 31, 37] (single- or double-blind) for OFC, and 321 (78.9%) of 407 patients with suspected CM allergy tested positive for OFC. Five studies [32, 34-36, 38] did not use blinding for OFC, and 428 patients received milk OFC, with 268 (62.6%) showing a positive reaction. In a study of CM allergy involving 123 patients [33], 26 (21%) underwent DBOFC, 51 (41%) underwent unblinded OFC, and the remaining patients did not undergo OFC. The thresholds for the fractions varied across studies and fractions. Five studies used the immunocap method to determine sIgE levels [32, 33, 35, 36, 38], one study used the microarray technique (ISAC CRD 51)[37], two studies used both ImmunoCAP and microarray technology[31, 34], one study used both ImmunoCAP and 3gAllergy technology.[30]
FIGURE 1 PRISMA Diagram for the literature search
3.3 | Quality assessment of included studies
Figure 2 summarizes the QUADAS-2 quality assessment for each study. Detailed QUADAS-2 assessment results are provided in Supplementary Information Table S3.