Nontuberculous mycobacterial infections in a Danish region between 2011 and 2021: evaluation of trends in diagnostic codes

Abstract

Introduction

Nontuberculous mycobacteria (NTM) are emerging as human pathogens at increasing rates. In Denmark, few studies of NTM exist, but these have not been able to confirm an increasing trend. Existing studies have not utilised clinical data or investigated geographical variations.

Methods

A retrospective cohort study of patients with an ICD-10 diagnostic code of NTM infection in a Danish region, Central Denmark Region, between 2011 and 2021. Incidence rates per 100,000 citizens were calculated using data from Statistics Denmark. A Spearman’s rank correlation coefficient was computed to assess the linear relationship between years and annual incidence rates.

Results

We identified 265 patients, 53.2% (n = 141) females, with a median age of 65.0 years (IQR 47–74). The age distribution was bimodal with peaks in extreme age groups between 0–14 years of age (n = 35, 13.2%) and above 74 years (n = 63, 23.8%). Most patients were coded with a pulmonary infection (51.3%, n = 136), 35.1% (n = 93) with other/unspecified infection and 13.6% (n = 36) with a skin infection. Incidence rates ranged from 1.3 (2013) to 2.5 (2021) per 100,000 citizens. There was a highly positive linear correlation of NTM incidence rates over the years (r = 0.75, p = 0.010) suggesting an increasing trend.

Conclusion

More than one-third with an NTM infection based on ICD-10 codes were found in extreme age groups. At least half of the patients had a pulmonary infection. Contradicting previous data from Denmark, we found an increasing trend of NTM, potentially suggesting an increase in clinically relevant disease, a higher awareness and test rate, or improved coding.

Keywords:

• Nontuberculous mycobacteria
• epidemiology
• trends
• geography

Acknowledgements

The authors thank Marianne Godt Hansen for her expertise and assistance with language revisions.

Ethical approval

The study was approved by local authorities in Central Denmark Region (1-45-70-33-22).

Author contributions

Conceptualisation, VND; methodology, VND, data curation, VND; writing – original draft preparation, VND; writing – review and editing, VND, AF and CW. All authors have read and agreed to the published version of the manuscript.

Disclosure statement

VND and AF participate in an advisory board for Nordicinfu Care Denmark, which distributes ARIKAYCE® (amikacin liposome inhalation suspension) for Insmed. CW has no conflict of interest to declare.

Additional information

Funding

The work by VND was performed during his PhD where he received funding from Department of Public Health, Aarhus University, Fonden af 17-12-1981, Skibsreder Per Henriksen, R. og hustrus fond, Region Midtjyllands Sundhedsvidenskabelige Forskningsfond, Christian Larsen og dommer Ellen Larsens Legat, Helga og Peter Kornings Fond, Fonden til Lægevidenskabens Fremme, The Danish Ministry of Higher Education and Science Elite Research travel grant, and Beckett-Fonden. The funders of the study had no role in study design, data collection, data analysis, data interpretation, or writing of the report.