Moving Beyond Responders: A Post Hoc Analysis Identifying Criteria for Chronic Cough Control.

BACKGROUND

Minimally important differences (MIDs) often define treatment response in refractory chronic cough (RCC). However, MIDs represent the smallest change in an outcome that patients perceive as important and do not indicate whether cough has improved to a level that would be considered adequately controlled. Therefore, defining criteria for cough control may provide a complementary benchmark for evaluating treatment success.

RESEARCH QUESTION: How can cough control be defined using thresholds anchored to patient-perceived sufficiency, and what proportion of patients achieve this state after treatment?

STUDY DESIGN AND

METHODS

The Prospective Study to Evaluate the Effectiveness of Guideline-Based Therapy for Chronic Cough and Refractory Chronic Cough (PROCOUGH) was a prospective, single-center observational cohort study conducted at McMaster University. Patients were treated according to European Respiratory Society guidelines with pretreatment and posttreatment assessments. Post hoc analyses based on the 90% upper limit of scores among patients reporting Global Rating of Change Scale scores of 6 or 7 and a treatment response question-"Is your cough sufficiently controlled that no additional treatment is required?"-were used to derive criteria for cough control. Patients not meeting cough control criteria were classified as having RCC.

RESULTS

One hundred patients completed follow-up (mean [SD] age, 58 [14] years; 58% female; median cough duration, 7 years). Controlled chronic cough (ConCC) was defined as post-treatment 24-hour cough frequency (CF) of ≤ 10 coughs/h, cough severity visual analog scale (CS-VAS) score of ≤ 30 mm, and Leicester Cough Questionnaire (LCQ) score of ≥ 16. After treatment, 26% of patients met all 3 criteria, whereas 74% met the definition of RCC. Using 2 patient-reported outcomes alone, 32% met ConCC criteria. Individually, LCQ, CS-VAS, and CF criteria were met by 36%, 44%, and 50% or patients, respectively.

INTERPRETATION: Our results show that we derived the following patient-anchored criteria for cough control incorporating objective and subjective outcomes: 24-hour CF of ≤ 10 coughs/h, CS-VAS of ≤ 30 mm, and LCQ score of ≥ 16. When these composite thresholds were applied to define ConCC, only 26% of patients achieved cough control, despite substantially higher proportions meeting individual responder criteria. This discrepancy underscores the need for improved treatments and outcome definitions that capture patient-perceived cough control.

CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov; No.: NCT04758351; URL: www.

CLINICALTRIALS: gov.