Prediction of Methotrexate Intolerance in Juvenile Idiopathic Arthritis: a prospective, observational cohort study

Table 3 Prediction model and scores for MTX intolerance

Predictors		OR (95%-CI)	p-value	β ^a	Score ^b
JIA category
Oligoarticular (persistent/extended)		Reference			0
Polyarticular (RF negative/positive)		4.99 (1.36-18.34)	0.016	0.914	5
Other (systemic/psoriatic/enthesitis)		0.93 (0.16-5.49)	0.935	−0.042	0
ANA	Positive	1.98 (0.83-4.68)	0.122	0.387	2
Parent/patient assessment of pain	≤3 cm	Reference			0
	3-6 cm	2.06 (0.72-5.89)	0.175	0.412	2
	>6 cm	0.60 (0.17-2.07)	0.421	−0.288	−1
JADAS-27	≤5	Reference			0
	5-15	0.35 (0.08-1.56)	0.168	−0.599	−3
	>15	0.77 (0.14-4.32)	0.766	−0.150	−1
Thrombocytes	>350 × 10⁹/L	1.27 (0.49-3.27)	0.621	0.136	1
ALT	>12 IU/L	0.39 (0.16-0.96)	0.040	−0.534	−3
Creatinine	>50 μmol/L	1.37 (0.33-5.67)	0.665	0.179	1
Interaction term creatinine: JIA category
>50 μmol/L & polyarticular arthritis		0.17 (0.02-1.35)	0.093	−1.022	−5
>50 μmol/L & other JIA category		0.82 (0.07-9.74)	0.878	−0.110	−1
Constant				−0.039	7
C-statistic		77.5%
C-statistic (optimism-corrected by bootstrap)		66.7%
Hosmer-Lemeshow test (p-value)		0.705

Abbreviations: ALT, alanine aminotransferase; ANA, anti-nuclear antibody; CI, confidence interval; JADAS, juvenile arthritis disease activity score; JIA, juvenile idiopathic arthritis; MTX, methotrexate; OR, odds ratio; RF, rheumatoid factor.
^aThese are shrunk coefficients (by factor 0.5688) to correct for overfitting.
^bShrunk coefficients were multiplied by 5 and rounded off to the nearest integer. The constant was adjusted to obtain the minimum score of 0.