Validity of ICD-10 diagnoses of overweight and obesity in Danish hospitals

Abstract

Purpose

Health care databases may be a valuable source for epidemiological research in obesity, if diagnoses are valid. We examined the validity and completeness of International Classification of Diseases, 10th revision [ICD-10] diagnosis coding for overweight/obesity in Danish hospitals.

Patients and methods

We linked data from the Danish National Patient Registry on patients with a hospital diagnosis code of overweight/obesity (ICD-10 code E66) with computerized height and weight measurements made during hospital contacts in the Central Denmark Region Clinical Information System. We computed the positive predictive value (PPV) of the IDC-10 diagnosis of overweight/obesity, using a documented body mass index (BMI) ≥25 kg/m² as gold standard. We also examined the completeness of obesity/overweight diagnosis coding among all patients recorded with BMI ≥25 kg/m².

Results

Of all 19,672 patients registered with a first diagnosis code of overweight/obesity in the National Patient Registry, 17,351 patients (88.2%) had any BMI measurement recorded in the Central Denmark Region Clinical Information System, and 17,240 patients (87.6%) had a BMI ≥25 kg/m², yielding a PPV of 87.6% (95% CI: 87.2–88.1). The PPV was slightly higher for primary diagnosis codes of overweight/obesity: 94.1% (95% CI: 93.3–94.8) than for secondary diagnosis codes: 86.1% (95% CI: 85.6–86.6). The PPV increased with higher patient age: from 75.3% (95% CI: 73.8–76.9) in those aged 18–29 years to 94.7% (95% CI: 92.6–96.9) in patients aged 80 years and above. Completeness of obesity/overweight diagnosis coding among patients recorded with BMI ≥25 kg/m² was only 10.9% (95% CI: 10.8–11.0).

Conclusion

Our findings indicate a high validity of the ICD-10 code E66 for overweight/obesity when recorded; however, completeness of coding was low. Nonetheless, ICD-10 discharge codes may be a suitable source of data on overweight/obesity for epidemiological research.

Keywords:

• obesity
• validation
• diagnosis code

Acknowledgment

The authors would like to thank Professor Henrik Toft Sørensen for sharing his expertise, guidance, and encouragement. The study was supported by the Independent Research Council, Denmark, the Novo Nordisk Foundation, and the department of Clinical Epidemiology, Aarhus University, Denmark. The funding sources had no role in the design, conduct, analysis, or reporting of the study.

Data availability

Data are available as presented in the paper. According to Danish legislation, our own approvals to use the Danish data sources for the current study do not allow us to distribute or make patient data directly available to other parties. Interested researchers may apply for data access through the Research Service at the Danish Health Data Authority (e-mail: kd.atadsdehdnus@ecivresreksrof; phone: [phone]). Up-to-date information on data access is available online (http://sundhedsdatastyrelsen.dk/da/forskerservice). Access to data from the Danish Health Data Authority requires approval from the Danish Data Protection Agency (https://www.datatilsynet.dk/english/the-danish-data-protection-agency/introduction-to-the-danish-data-protection-agency/). The authors do not have special access privileges to these data.

Disclosure

The authors report no conflicts of interest in this work.