Predicting phenotypes at risk of chronic obstructive pulmonary disease (COPD) exacerbation is extremely important. Dysphagia is becoming recognized as one of these phenotypes. A convenient method of screening for dysphagia and COPD exacerbation risk is desired. The repetitive saliva swallowing test (RSST) is one of the least invasive dysphagia screening methods. We previously reported the possible relation between the RSST result and COPD exacerbation in a retrospective study. Based on this, we performed a prospective study to evaluate the efficacy of RSST as a predictor of COPD exacerbation and to determine its optimal cut-off value for COPD.
Seventy patients with COPD were recruited. Patients underwent the following dysphagia screening tests: the 10-item Eating Assessment Tool, Frequency Scale for the Symptoms of Gastroesophageal Reflux Disease, RSST, water swallowing test, and simple swallow provocation test. After one year, they were classified into two groups according to the presence of COPD exacerbation during the follow-up period.
Twenty-seven patients had one or more exacerbations in the past year. During the follow-up period, 28 patients had one or more exacerbations (E group), and 42 had none (non-E group). There were no significant differences between the groups except for the presence of past exacerbations and the results of the RSST, when the cut-off value was set at 2, 3, 4, or 5 swallows. The number of swallows in the RSST was significantly lower in the E group than in the Non-E group. A cut-off value of 5 was the most effective. The time to first exacerbation was significantly longer in those with an RSST value of >5. The RSST was more reliable for differentiating the E group and non-E group than the presence of exacerbation in the past year (hazard ratios: 13.78 and 2.70, respectively).