Recent studies about the use of Traditional Chinese Medicine (TCM) to treat cough variant asthma (CVA) , a common respiratory disease, are increasing. TCM has proven to be effective in improving symptoms and the overall treatment efficacy of CVA, but relevant research is still in the exploratory stage, and there are no unified and standardized diagnostic criteria for CVA.

To explore the common syndromes and symptom characteristics of CVA.

The literature related to CVA syndromes or symptoms treated by TCM was searched in CNKI, Wanfang Data, VIP, and SinoMed databases from inception to October 2, 2021. SPSS 25.0 software was used to support the input of extracted information to establish a database, and the statistical treatment of the frequencies of CVA-related syndromes and symptoms. The symptoms with a frequency over 5% were selected for factor analysis, and the common factors were extracted for further hierarchical cluster analysis, and the potential syndromes were inferred from the results. Using Lantern 5.0 software, based on the LTM-EAST (Latent Tree Model-Extension Adjustment Simplification until Termination algorithm) , a latent structure model was constructed and a comprehensive cluster analysis was performed to infer potential syndromes. Then the common syndromes and symptom characteristics of CVA were obtained by combining the results of frequency statistics, hierarchical clustering, and latent structure analysis.

A total of 621 studies were included, involving 115 symptoms, including cough, pharyngeal itching, low sputum volume, etc. Thirty-nine syndromes were involved, among which the highly frequent syndromes were pathogenic wind invading the lung, wind and cold invading the lung, and lung yin deficiency. Six potential syndromes were derived from hierarchical cluster analysis, including wind and heat invading the lung, liver fire invading the lung, lung qi deficiency and so on. The latent structure analysis was performed on the symptoms with frequency over 3%, by which 21 latent variables, and 42 latent classes were obtained, and 12 potential syndromes were further inferred by comprehensive clustering, including pathogenic wind invading the lung, wind and cold invading the lung, wind and heat invading the lung, and so on. Based on the above analyses, 11 common syndromes were finally identified. Each syndrome has specific symptom characteristics, for example, the syndrome of pathogenic wind invading the lung manifests itself as cough, sneezing, running nose, and nasal congestion.

We identified 11 common syndromes of CVA with typical symptom characteristics, which are pathogenic wind invading the lung, wind and cold invading the lung, wind and heat invading the lung, wind and dryness damaging the lung, phlegm and heat congesting in the lung, phlegm and dampness accumulating in the lung, liver fire invading the lung, cold fluid retention in the lung, lung qi deficiency, lung yin deficiency, and lung-spleen qi deficiency. Our analysis will provide a basis for clinical syndrome differentiation and clinical investigation of CVA.