Transepidermal water loss (TEWL) and transonychial water loss (TOWL) measurements in healthy nail apparatus.

BACKGROUND: Although non-invasive diagnostic methods are widely used to examine the nail apparatus (NA), studies in healthy ones are scarce, and analyzes were often conducted in small groups. In the literature, there are only a few reports on TOWL measurements. The results of TEWL studies in the proximal nailfold have not been published so far. MATERIALS AND METHODS: Based on a detailed interview and physical examination, 81 volunteers (40 women and 41 men) aged from 22 to 65 years were qualified for the study. In this study, the overall examination of the NA in relation to water loss was performed for the first time, regarding the hand (d, dominant; n, non-dominant) and finger types (number, start of count from thumbs) as well as sex and age. RESULTS: The average TEWL value in the entire group ranged from 7.53 c.u. in the finger nd4 to 11.09 c.u. in nd1. Both in the dominant and non-dominant hand, in the entire analyzed group, and taking into account gender, weak statistically significant relationships were observed between the finger type value and TEWL (p < 0.05).The TEWL values were lower moving away from the thumb, The average TOWL value in the entire group ranged from 5.01 c.u. in d1 to 7.34 c.u. in d5. Both in the dominant and non-dominant hand, in the entire analyzed group and considering gender, statistically significant relationships were observed between the type of finger and TOWL values (p < 0.05). The TOWL values were higher moving away from the thumb. Subsequently, the values of TOWL and TEWL did not depend on type of hand (dominant or non-dominant), sex and age. Weak and moderate statistically significant correlations were found between TEWL and TOWL values in the entire study group and in females, as well as in selected fingers in males (d2, nd2, d3, nd3, d5, nd5) (p < 0.05, r < 0.27). CONCLUSION: Non-invasive diagnostics such TEWL and TOWL measurements are useful to assess differences in structure and function between types of fingers. However, obtained results demand further studies.

High-Frequency Ultrasonography and Evaporimetry in Non-invasive Evaluation of the Nail Unit.

Background: The nail unit (NU) is a complex structure that performs a number of functions, including protection, defense, manipulation, and palpation. Non-invasive research methods can facilitate the recognition of NU structure and function. Evaporimetry and HF-USG due to their availability of equipment and low research costs seem to be particularly noteworthy, but so far have been assessed to a limited extent. The aim of the presented study was to check the usefulness of TOWL and HF-USG in examination of NU. Materials and Methods: A total of 58 volunteers aged 25-65 years (mean age: 41 ± 10.16 years) were qualified for the study. The subjects did not present symptoms of clinically evident onychopathy and did not suffer from any dermatoses associated with lesions occurring within the NU. Additionally, the patients did not suffer from systemic diseases that could affect NU (including heart, lung, and endocrine diseases). In all volunteers, the measurement of TOWL and 20 MHz ultrasonography [high-frequency ultrasonography (HF-USG)] with the special emphasis on determination of nail plate thickness were performed. Results: Analysis of 464 HF-USG images revealed that the nail plate presented as two hyperechoic, parallel streaks (railway sign) with a linear hypoechoic middle layer between them. Matrix was visualized as a hypoechoic structure with blurred boundaries, mostly within the fourth and fifth fingers and more often in women. We found statistically significant correlations between the type of a finger and the thickness of the nail plate both in the entire study group and taking into account gender. In the dominant hand, the results were r = -0.341; p < 0.001; r = -0.417, p < 0.001; and r = 0.337; p = 0.001 (for the whole group, for women, and for men, respectively). In the non-dominant hand, the results were r = -0.465; p < 0.001; r = -0.493, p < 0.01; and r = -0.503; p < 0.01 (for the whole group, for women, and for men, respectively). There were statistically significant differences in the thickness of the nail plates of the corresponding types of fingers between female and male NUs. Statistically significant correlations were found between the type of a finger and the TOWL value in the whole group and taking into account gender (p < 0.05), except for the non-dominant hand in men. There were no statistically significant differences in the TOWL values of the corresponding types of fingers between male and female NUs (p > 0.05). There was no statistically significant correlation between the TOWL value and the nail plate thickness in any of the tested NUs, apart from the one statistically significant correlation in nd5 (r = 0.390, p = 0.021). Conclusions: To sum up, non-invasive methods, such as HF-USG and TOWL, enable assessment of the NU and are useful in examination of its structure and function. HF-USG shows characteristic elements of NUs that can be distinguished because of differences in their echogenicity. The thickness of the nail plate and TOWL depend on the type of finger, and show a relationship with gender.