Covariates Regression coefficient RDOR (95% CI) P value Type of study (prospective vs. respective) -0.294 0.75 (0.06-8.68) 0.7707 Data assessment (qualitative vs. semi-quantitative) 1.017 2.77 (0.38-20.22) 0.2659 Blinding (yes vs. no) 3.288 26.78 (3.52-203.44) 0.0057 Type of imaging (PET vs. PET-CT) -2.030 0.13 (0.01-1.68) 0.0993

Table 3: Meta-regression analysis for possible sources of heterogeneity between studies of patients with multiple myeloma. PET: Positron Emission Tomography; PET-CT: PET-Computed Tomography; RDOR: Relative Diagnostic Odds Ratio; CI: Confidence Interval.