(709) Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP) as Measures of Inflammation in Chronic Cough

Introduction: Chronic cough has been associated with inflammatory states that result in excitation of the P2X3 ATP channel receptor. Given that elevated ESR and CRP are seen in inflammation, we hypothesize that elevated ESR and CRP are seen in patients with chronic cough and may serve as a tool for monitoring disease.

Methods: In this retrospective case-control study performed within the Geisinger Health System, patient data including demographics, cough encounter data, and laboratory values from patients with a diagnosis of cough between January 1, 2021, and December 31, 2023 were extracted.

Results: 101,644 patients had a visit for cough in the study period. 15,326 patients had at least one ESR drawn, and 19,741 had at least one CRP drawn. Of those, 10,319 patients were classified as having a chronic cough, with chronicity defined as having two or more visits more than 8 weeks apart. In those patients who had either ESR or CRP data, chronic cough patients were more likely to be female (mean difference: 3.7%, 95% CI: 2.4%, 6.1%; p-value: < 0.001) and slightly older (mean difference: 0.84 years; 95% CI: 0.17, 1.51; p-value = 0.014) compared to patients without chronic cough. As the number of encounters for evaluation of cough increased to 6 or greater, the CRP levels were found to increase, with a peak CRP level of 22.8 mg/dL (SD 37.5).

Conclusions: Increasing CRP with number of encounters suggests that worse or prolonged refractory chronic cough is associated with a generalized inflammatory state. An inflammatory state is consistent with our current understanding of ATP driven P2X3 receptor proliferation in seen in refractory chronic cough.