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Validation of asthma and eczema in population-based Swedish drug and patient registers

Authors

  • Anne K. Örtqvist,

    Corresponding author
    • Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
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  • Cecilia Lundholm,

    1. Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
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  • Björn Wettermark,

    1. Centre for Pharmacoepidemiology, Department of Medicine, Karolinska Institutet, Stockholm, Sweden
    2. Public Healthcare Services Committee Administration, Stockholm County Council, Stockholm, Sweden
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  • Jonas F. Ludvigsson,

    1. Department of Pediatrics, Örebro University Hospital, Örebro, Sweden
    2. Clinical epidemiology unit, Department of Medicine, Karolinska Institutet, Stockholm, Sweden
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  • Weimin Ye,

    1. Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
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  • Catarina Almqvist

    1. Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
    2. Department of Women's and Children's Health, Astrid Lindgren Children's Hospital, Karolinska University Hospital, Stockholm, Sweden
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Correspondence to: A. K. Örtqvist, Department of Medical Epidemiology and Biostatistics, PO Box 281, Karolinska Institutet, SE-171 77, Stockholm, Sweden. E-mail: anne.ortqvist@ki.se

ABSTRACT

Purpose

Validated measures of asthma and eczema at the population level remain a challenge. Our aim was to ascertain if register-based information on asthma/eczema medication can function as a proxy for an asthma/eczema diagnosis and to validate register-based asthma diagnoses.

Methods

Information was requested on all 0–45-year-old individuals with reported asthma/eczema medication and/or diagnoses in the Swedish Prescribed Drug Register and National Patient Register, between July 2005 and December 2009 (N = 250 691). Medical records for 1952 randomly selected individuals were reviewed to estimate the proportion of individuals with the following: (1) asthma/eczema medication that fulfilled predefined criteria of asthma/eczema (positive predictive value (PPV)) and (2) a register-based asthma diagnosis verified as asthma by predefined criteria.

Results

Positive predictive value for asthma by predefined criteria ranged between 0.75 (95%CI: 0.70–0.78) to 0.94 (95%CI: 0.91–0.96), depending on age group. In pre-school children, PPV for asthma in combination with obstructive bronchitis was 0.87 (95%CI: 0.83–0.90), and PPV for eczema was estimated to 0.45 (95%CI: 0.38–0.51). Eighty percent of children 0–4.5 years and 99% of children >4.5–17 years with a register-based diagnosis of asthma were verified as asthmatics.

Conclusion

Asthma medication is a suitable proxy for asthma in older children and adults; the same approach is insufficient for eczema. This validation study of two Swedish registers opens for future large nation-wide register-based studies on asthma. Copyright © 2013 John Wiley & Sons, Ltd.

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