Multidrug-resistant tuberculosis in Norway: a nationwide study, 1995-2014.

Setting: The management of multidrug-resistant tuberculosis (MDR-TB) is strictly regulated in Norway. However, nationwide studies of the epidemic are lacking.

Objective: To describe the MDR-TB epidemic in Norway over two decades.

Design: Retrospective analysis of data on MDR-TB cases in Norway, 1995-2014, obtained from the national registry, patient records and the reference laboratory, with genotyping and cluster analysis data. Data for non-MDR-TB cases were collected from the national registry.

Results: Of 4427 TB cases, 89 (2.0%) had MDR-TB, 7% of whom had extensively drug-resistant TB (XDR-TB) and 24% pre-XDR-TB. Of the 89 MDR-TB cases, 96% were immigrants, mainly from the Horn of Africa or the former Soviet Union (FSU); 37% had smear-positive TB; and 4% were human immunodeficiency virus co-infected. Of the 19% infected in Norway, the majority belonged to a Delhi/Central Asian lineage cluster in a local Somali community. Among the MDR-TB cases, smear-positive TB and FSU origin were independent risk factors for XDR/pre-XDR-TB. Treatment was successful in 66%; 17% were lost to follow-up, with illicit drug use and adolescence being independent risk factors. Forty-four per cent of patients treated with linezolid discontinued treatment due to adverse effects.

Conclusion: MDR-TB is rare in Norway and is predominantly seen in immigrants from the Horn of Africa and FSU. Domestic transmission outside immigrant populations is minimal.