GP1BA and juvenile idiopathic arthritis: Higher GPIbα level instrumented by trans‐pQTL was also associated with a higher risk of JIA (OR 3.01 [95% CI 1.64–5.51], P = 3.66 × 10−4) (Figure 2 and Supplementary Table 5, available on the Arthritis & Rheumatology website at http://onlinelibrary.wiley.com/doi/10.1002/art.41561/abstract).