Heterogeneity of outcome measures used in randomized controlled trials for the treatment of oral lichen planus: a methodological study

Introduction
Oral lichen planus (OLP) is a chronic inflammatory immune disease, recognized as an oral potentially malignant disorder by the World Health Organization (WHO). There is considerable controversy over the standardized treatment of OLP, with great diversities in the outcome measures in clinical trials.

Objective
This methodological study aimed to estimate the degree of consensus on outcome measures in randomized controlled trials (RCTs) for OLP treatment.

Materials and Methods
PubMed, Embase, and Cochrane databases were searched to identify RCTs published from 2004 to 2018 about OLP treatment. All the outcome measures and measurement methods mentioned in the trials were extracted and analyzed.

Results
After identification of 1087 articles, 88 RCTs were included. A total of 193 single outcome measures and 119 composite outcome measures were classified into 11 different domains, the chief of which consisted of clinical symptom (78 trials; 88.6%) and clinical score (58 trials; 65.9%). Visual analog scale (65 trials; 73.9%) and Thongprasom scoring system (38 trials; 43.2%) were the predominant measurement methods. Oral health-related quality of life (except for clinical symptoms) accounted for 4.8% of all the outcome measures.

Conclusions
There was high heterogeneity in outcome measures of RCTs for OLP treatment, making it difficult to make valid comparisons between different clinical trials. A core outcome set should be developed and adopted in future trials for OLP treatment.