Clinical Signs and Laboratory Tests for the Differential Diagnosis ofAndrogenic and Post-COVID-19 Alopecia in Women

Background: Pathological hair loss in women has emerged as a prevalent cause for seeking specialized dermatological and cosmetic services. The most common type of this condition is androgenetic alopecia, which arises due to hormonal and micronutrient imbalances.Furthermore, during the COVID-19 epidemic, there has been a notable increase in the number of female patients with pathological hair loss as a complication of the disease, with some individualsexperiencing alopecia the sole indication of asymptomatic COVID-19. Aims: The aim of the study wassearch for objective criteria for the differential diagnosis of androgenetic alopecia and post-COVID alopecia in women based on informative trichological and laboratory markers. Materials and methods: The including criteria for androgenetic alopecia (AGA) group were elevated dihydrotestosterone (DHT) levels, clinical indications of alopecia corresponding to initial stages of the condition, and a past experience of continuous observation untilFebruary 2020. For the post-COVID alopecia (COVID) group, inclusion criteria were a confirmed diagnosis of COVID-19 using RT-PCR and the presence of alopecia symptoms emerging within a year post-infection. Evaluation of quantitative characteristics of hairs was conducted was carried out based on trichogram and phototrichogram data, followed by image processing using a computer diagnostic program. Key indicators for hair growth were identified in patients' plasma, including DHT, vitamins B9 (folic acid), B12, D (25(OH)-D3 form), E, as well as calcium (Ca), iron (Fe), magnesium (Mg), selenium (Se), copper (Cu), and zinc (Zn). CART algorithm (Classification and Regression Trees) based on recursive partitioning of available data with selection of informative predictors and formation of a tree-like hierarchical structurewas applied to determine criteria to differentiate between patients with androgenetic and post-COVID alopecia. Results: Analysis of trichograms and phototrichograms revealed that unlike androgenetic alopecia, which primarily impacts hair follicles in the telogen and anagen phases in the androgen-dependent zone, post-COVID hair loss presents as a diffuse telogen effluvium pattern, involving the androgen-dependent (parietal) area of the scalp. Notably, patients with post-COVID alopecia exhibited elevated dihydrotestosterone levels compared to reference values, with no significant differencein comparison to AGA. While there were no variations in vitamin and certain trace element levels (Fe, Ca, Mg, Zn), individuals in COVID group have demonstrated a statistically significant reduction in copper content (46.4% lower than AGA; p=0.006) alongside an increase in selenium levels (24.7% higher than AGA; p=0.003). Conclusions: The performed study for the first time presents objective criteria for the differential diagnosis of androgenetic and post-COVID alopecia in women. The data obtained show a diffuse pattern of telogen effluvium after recovering from COVID-19, linked to an imbalance in trace elements - specifically, a decrease in copper (Cu) and an increase in selenium (Se). Based on this fact, the algorithm CART used allows for a highly effective differentiation of the compared variants of pathological hair loss in studied patients and forms the basis for pathogenetically justified conservative therapy.