A new index to assess the severity of Lichen planus in clinical practice

Purpose. Development and validation of the severity index of lichen planus (LP).

Materials and methods. At the first stage, by means of theoretical substantiation, the main parameters and signs were identified that affect the severity of the disease and the quality of life of patients, which culminated in the derivation of the final index formula, which was called the lichen area and severity index (LPASI). At the second stage, LPASI was validated during the examination of 45 LP patients who were treated in the clinic of skin and venereal diseases of the Military Medical Academy in 2018—2019. Determination of LPASI was carried out by five dermatovenerologists independently of each other twice with an interval of one week.

The analysis of the results was carried out using STATISTICA 10.0 programs and SPSS Statistics 17.0. The Spearman — Brown and Pearson correlation coefficients were used to evaluate the intra-expert and inter-expert reliability of the index, and the Cronbach's alpha coefficient was calculated to assess the internal consistency of the scale.

Results. The final formula for calculating LPASI is as follows: 0.2 × A + 2 × B + 5 × С + D, where A is the area of skin lesions in percentage, B is the severity of clinical manifestations on the skin, C is the severity of clinical manifestations on the oral mucosa and D is the severity of subjective sensations. The index can range from 0 to 82.

The LPASI values for the whole group (n = 45) were characterized by a normal distribution of the trait (p > 0.05), the minimum and maximum values varied from 7.2 to 42 points, the median was 22 points, the interquartile span from 14 to 27 points. The values of the Spearman — Brown and Pearson coefficients were equal to 0.91 (95% CI — 0.89—0.99) and 0,87 (95% CI — 0.86—0.93), which indicates the reproducibility of the results and the reliability of the index. In this case, a high consistency between the selected features within the scale (Cronbach's alpha criterion — 0.93) was established.

Conclusion. Objectification of the severity of the disease using LPASI should become an integral part of the clinical examination of patients. The use of LPASI will allow to control the effectiveness of prescribed therapy, as well as to compare the results of scientific research.