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Table 4 Item response theory unidimensional model of the HIT-6 at PROMISE-2 baseline

From: Reliability and validity of the 6-item Headache Impact Test in chronic migraine from the PROMISE-2 study

Item Item content a (SE) b1 (SE) b2 (SE) b3 (SE) b4 (SE)
1 Severe pain 1.12 (0.09) ‒3.72 (0.29) ‒0.68 (0.08) 2.86 (0.21)  
2 Limits daily activities 2.33 (0.14) ‒2.07 (0.10) ‒0.31 (0.05) 1.62 (0.08)  
3 Lie down 1.34 (0.09) ‒3.37 (0.23) ‒1.67 (0.11) 0.32 (0.06)  
4 Too tired 3.28 (0.23) ‒2.67 (0.14) ‒1.46 (0.06) ‒0.14 (0.04) 1.63 (0.08)
5 Felt fed up or irritated 1.45 (0.09) ‒3.47 (0.23) ‒1.99 (0.12) ‒0.43 (0.06) 1.35 (0.09)
6 Limits concentration 3.52 (0.27) ‒2.72 (0.15) ‒1.59 (0.07) ‒0.31 (0.04) 1.39 (0.06)
  1. a slope, b thresholds, HIT-6 6-item Headache Impact Test, SE standard error