Establishing accurate case definitions for childhood respiratory and skin conditions

A research letter addresses the challenges of accurately diagnosing asthma, atopic eczema, and allergic rhinitis in children under 5 years old and the use of Read codes and prescription data as diagnostic criteria.

Recommended diagnostic definitions have been presented for 3 common allergic diseases: asthma, atopic eczema, and allergic rhinitis. These definitions were developed using electronic health record (EHR) data from general practitioners (GPs) in the UK, which included both diagnoses and prescriptions.

A new research letter from Sergio Souza Da Cunha, Bradford Teaching Hospitals NHS Trust, Bradford Institute for Health Research, and investigators, addressed the challenges in defining clinical outcomes, specifically related to the diagnosis of asthma and allergic diseases (AAD) in young children using electronic health record (EHR) databases. The accuracy of diagnostic codes depends on various factors, and the impact of disease misclassification can be significant.

Recommendations on defining asthma, atopic eczema, and allergic rhinitis

They presented definitions for asthma, atopic eczema, and allergic rhinitis, including the selected Read codes and prescriptions required for each, with the first definition for asthma requiring either a Read code or prescription, the first definition for eczema requiring a Read code and two eczema-related prescriptions, and the first definition for allergic rhinitis requiring a Read code only, while the second definition requires a Read code and prescription during hay fever season.

In addition to their use of established methods,investigators consulted with experts in the field to refine and improve their case definitions. By combining these different approaches, they were able to create case definitions that were both rigorous and flexible, capable of capturing the full range of cases of each disease while avoiding misclassification.

As a result, the investigators recommended that other researchers consider using a similar approach in their own studies. Given the complexity and variability of allergic diseases, the use of EHR data and the involvement of experts in the field can help ensure that case definitions are accurate, consistent, and well-suited to the specific research question at hand.

According to the letter, standardizing case definitions in this way, future investigations can increase the comparability and generalizability of findings, ultimately advancing our understanding of these common and often debilitating conditions.

Assessing the diagnostic inconsistencies for children with respiratory and skin conditions

To ensure the accuracy and reliability of definitions, existing definitions were adapted from previous studies and used text mining techniques to identify relevant Read codes. The letter presented an approach to defining AAD outcomes using CTV3 Read codes and British National Formulary (BNF) codes for prescriptions of medications.

Case definitions for the diagnosis of asthma, atopic eczema, and allergic rhinitis conditions based on selected Read codes and prescriptions were examined for challenges of differential diagnosis.

For asthma, the first definition requires the presence of selected Read codes at 6 years old or regular prescriptions for asthma at 6 years old after Read codes between 3-5 years old. The second definition requires the presence of selected Read codes at 3 years or older. For atopic eczema, the first definition includes selected Read codes and at least 2 prescriptions of eczema-related treatment within 90 days before or 365 days after the first recorded diagnosis.

However, the revised definition only requires the presence of relevant Read codes. For allergic rhinitis, the first definition is based on Read codes only, and the second definition includes a subset of children with a Read code between March and July who were also prescribed medication. Ultimately investigators concluded, prescriptions can be useful for asthma case definitions, but less so for eczema and allergic rhinitis, where over-the-counter remedies are widely available.

This article was published by our sister publication HCP Live.

Reference

1. Souza da Cunha, S., Santorelli, G. and Pembrey, L. Defining cases of asthma, eczema and allergic rhinitis using electronic health records in the Born in Bradford birth cohort. Clin Exp Allergy. 2023. doi:10.1111/cea.14291