Introduction and Objectives Current understanding of IPF proposes repetitive pulmonary epithelial injury with aberrant healing as a principal mechanism. Gastro-oesophageal reflux (GOR) and micro-aspiration of gastric contents may cause lung injury with subsequent fibrosis, and GOR is known to be prevalent in IPF patients. We assessed the feasibility of salivary pepsin measurement in IPF patients and investigated the temporal variability and relationship between salivary pepsin and symptoms.
Methods IPF patients collected saliva samples at multiple time points over the course of one day. Early morning, lunch- and dinner-time samples were analysed and compared with results from a historical control group of 100 healthy volunteers. Samples were analysed for the presence of pepsin using Peptest™ (RD Biomed Ltd). Patients were defined as pepsin positive if they had pepsin detectable in at least 1 saliva sample. The St George’s Respiratory Questionnaire (SQRQ), Hull Airways Reflux Questionnaire (HARQ), and the REFLUX questionnaire were used to assess the relationship between pepsin positivity and symptoms.
Results All 21 IPF patients successfully provided saliva samples, of which 17 patients (81%) were pepsin positive compared to 36 of 100 healthy volunteers (36%), p = 0.0004. The proportion of subjects with 1, 2 and 3 positive samples during a 24 hour period were 52%, 14% and 14% respectively in IPF patients and 20%, 12% and 4% in control subjects. There was no significant difference in reflux-related quality of life or respiratory quality of life between pepsin positive and pepsin negative patients measured using the REFLUX questionnaire (mean 93.6 ± 2.6 SEM vs 97.8 ± 2.3, p = 0.47) and SGRQ (49.5 ± 3.5 vs 34 ± 11.9, p = 0.1). The HARQ score was significantly higher in pepsin positive patients (23.8 ± 3.3 vs 7.5 ± 3.3, p = 0.03).
Conclusion Salivary pepsin measurement is simple, convenient and acceptable to patients. Our results confirm an increased prevalence of positive salivary pepsin in IPF patients compared to healthy volunteers but demonstrate a marked temporal variability. Therefore, more than one sample or repeated sample collection is required for optimal sensitivity.