Validation of International Classification of Diseases Diagnosis Codes for Anaemia During Pregnancy.

BACKGROUND

Anaemia during pregnancy is common and increases the risk of adverse perinatal outcomes. Epidemiologic research on anaemia during pregnancy largely relies on International Classification of Diseases, Clinical Modification, 10th Revision (ICD-10) diagnosis codes, despite limited evidence on their validity.

OBJECTIVE

Our objective was to assess the validity of ICD-10 codes against haemoglobin and haematocrit values in identifying anaemia during pregnancy.

METHODS

We utilised the Merative™ MarketScan® Commercial Database, a national database of commercial insurance claims with laboratory values during 2018-2022. We included pregnancies with ≥ 1 haemoglobin or haematocrit value measured during pregnancy and excluded pregnancies with a hereditary anaemia diagnosis code. We used established criteria to define anaemia and assessed the validity of the diagnosis codes against laboratory values by calculating Cohen's kappa, sensitivity, specificity, and positive and negative predictive value.

RESULTS

Among 71,160 pregnancies, concordance between anaemia identified through laboratory values and ICD-10 codes was 0.258 (95% confidence interval [CI]: 0.248, 0.268), sensitivity was 0.300 (95% CI: 0.294, 0.307), specificity was 0.918 (95% CI: 0.916, 0.921), positive predictive value was 0.551 (95% CI: 0.541, 0.561), and negative predictive value was 0.797 (95% CI: 0.794, 0.801).

CONCLUSIONS

We found in a nationwide commercial claims database with measured laboratory values that ICD-10 diagnosis codes for antepartum anaemia have low sensitivity and high specificity. Researchers should be cautious when using ICD-10 codes alone to identify antepartum anaemia and should consider bias analyses to reduce misclassification error.