Developing a PROM to Measure Severity of Chronic Cough

Researchers recently described efforts to create a patient-reported outcome measurement (PROM) tool that specifically identifies the severity of chronic cough symptoms. The meta-analysis appears in the European Respiratory Review.

Existing metrics to measure cough symptoms are not totally comprehensive and have limitations like prohibitive expense, a timeframe limited to 24 hours, and are difficult for patients to use. Patient-reported outcomes (PROs) are limited by focusing on the impact on quality of life, which thus only indirectly tracked cough severity, the authors said.

Other chronic cough measurements include the Visual Analogue Scale (VAS), Cough Symptom Score (CSS), and proprietary Cough Severity Diary (CSD). All have limitations in measuring severity as well, the authors said.

The researchers combed databases for works published from January 2007 to August 2020 and included terms representing cough and PRO measurement. Out of 6425 titles and abstracts and 334 full texts, 61 eligible studies were included.

The taxonomy used to form the categories for cough severity were created using keywords extracted for their content and meaning in a qualitative synthesis of the materials. Vote counting was then used to identify how frequently which authors mentioned the subdomains in order to produce the final conceptual framework.

In the process, the authors also observed that the average patient with chronic cough were women aged 50 years or older, nonsmokers, and were receiving secondary or tertiary care.

The survey identified 82 potential items, of which 43 proved unique and were clearly related to cough severity in unexplained or refractory chronic cough. The 43 items were categorized under 2 broad domains, the urge-to-cough and cough symptom. Subdomains included frequency, duration, control, and intensity.

A few limitations were noted. Most of the studies pulled from the database were published after 2007, though this did not prevent pertinent articles from earlier years being included. Furthermore, the way the domains were gathered was through sorting verbatim quotes, which introduces what the authors admit is an element of subjectivity through interpretation to their categories. The conceptual framework used by the authors does not consider duration of bouts or other quality of life factors, but does identify cough control, frequency, and intensity of the urge-to-cough sensation as subdomains for assessment of cough severity.

Ideally, the development of the PROM may aid in the treatment of the estimated 2% to 18% of adults worldwide who experience a chronic cough lasting greater than 8 weeks, 60% of whom may continue to experience symptoms even after treatment for potential causes.

Overall, the authors felt this gap in information needs to be filled and that along with understanding quality of life issues, “full insight into therapeutic efficacy requires assessment of cough symptom severity itself.” A new PROM developed from this research could complement the use of these scales, they said.

Reference

Kum E, Guyatt G, Devji T, et al. Cough symptom severity in patients with refractory or unexplained chronic cough: a systematic survey and conceptual framework. Eur Respir Rev. Published online July 13, 2021. do: 10.1183/16000617.0104-2021