Rheumatoid arthritis (RA) is a chronic inflammatory disease affecting mainly smaller joints. Patients are at risk for complications as joint destruction, but starting treatment soon after onset of disease, has reduced the risk for complications. Methotrexate (MTX) is the anchor drug in the treatment of RA and has proven effects on both inflammatory symptoms and joint destruction. apy. Identifying patients at risk for MTX-induced hepatotoxicity before treatment could be a way to minimize the risk for Adverese effects.Following the introduction of pre-treatment screening, the risk of tuberculosis (TB) among patients with RA starting biologic treatment has decreased. By contrast, the risk remains several-fold increased in RA patients non-exposed to biological treatment. Knowledge about risk factors for TB and TB characteristics in this group of patients, and thus optimal clinical risk stratification and preven-tion, is still limited.In Paper I, only a small number of ALT tests (7%) performed during MTX therapy in RA patients, capture an elevation of ALT > upper limit of normal (ULN). ALT >1.5 × ULN was observed in 44 (21%) patients and the strongest predictor was a pre-treatment elevation of ALT. Recurrent elevations occurred in 70% of patients who continued treatment, and the proportion was similar in those with and without interventions. The results support a more individualized approach to monitoring and handling of ALT elevations during MTX therapy. In Paper II MTHFR A1298C (rs1801131) was nominally associated with ALT >1.5 x ULN within 6 months after the start of MTX (OR=1.7 [95% CI 1.04-2.9], p=0.03). In a multi-ple regression analysis for ALT >1.5 X ULN within 6 months of treatment start, including known risk factors for ALT elevation and MTHFR A1298C, the C-statistic was 0.734. A mod-el containing clinical risk factors and MTHFR A1298C might be used for prediction of ALT elevation in MTX treated patients. In Paper III a Genome-Wide Association Study (GWAS) and analysis of candidate Single Nucleotide Polymorphisms (SNPs) were performed. Four SNPs in and upstream of the ribonucleoprotein, PTB Binding 2 gene on chromosome 1 were associated with max ALT within 6 months on a genome wide level (p<5x10-8). Our results indicate that the RAVER2 and/or JAK1 genes might play a role in MTX- induced hepatotoxici-ty, but further studies are necessary for confirmation of the results. In Paper IV, we performed a population based case-control study. Several RA-associated risk factors (treatment with leflunomide, azathioprine or prednisolone and concomitant obstructive lung disease) may contribute to the increased TB risk in biologics-naïve RA patients. We could not confirm previous findings of an association with the use of moderate to high doses of prednisolone (≥15 mg). TB risk seems difficult to predict with precision in the individual biologics-naïve patient based on RA-associated risk factors. This suggests TB screening should be considered in biologics-naïve patients.

In conclusion, results from these studies suggest that several factors could increase the risk of AEs in RA patients. The risk might be reduced by utilizing prediction models that include knowledge about the medical history of the individual patient and genetic data in combination with screening for TB.