Effect of skin phototype on quantitative nailfold capillaroscopy

Abstract

Objectives: To determine the impact of Fitzpatrick scale-based skin phototype on visualization of capillary density using nailfold capillaroscopy in healthy Indian adults. Methods: In this cross-sectional study, healthy adults were examined for nailfold capillaroscopy findings utilizing a portable capillary microscope at 800× magnification. Photographs of two contiguous areas measuring 1 mm2 each of the distal row of capillaries were captured. Images were captured from the central area of all fingers except thumb in both hands. Capillary density and morphology of nailfold capillaroscopies were assessed by two blinded assessors. The nailfold capillaroscopy parameters were compared between the Standard Fitzpatrick scale-based skin phototypes. Results: A total of 118 healthy adults were enrolled in the study. Type III, IV, V, and VI skin phototypes were seen in 27 (22.90%), 32 (27.19%), 29 (24.58%), and 30 (25.42%) participants, respectively. All participants (100%) had normal nailfold capillaroscopy morphology and architecture. Zero capillaries were visible in 11 fingers among 5 patients (4.24%) and all of them had Type VI phototype. The median capillary density per mm was 5.19 (interquartile range = 4.37–6.75) with 90 (76.27%) participants having less than seven capillaries. The median average capillary density was significantly different ( p-value < 0.0001) across Type III (8.13, interquartile range = 6.44–8.88), Type IV (5.67, interquartile range = 4.41–6.98), Type V (4.94, interquartile range = 4.19–5.38), and Type VI (4.53, interquartile range = 3.72–4.91) phototypes ( p < 0.05). Conclusion: The number of capillaries visualized during nailfold capillaroscopy decreases as the skin pigmentation increases. There is a need to redefine the nailfold capillaroscopy density and avascularity by taking skin phototype as one of the determinants before labeling a nailfold capillaroscopy finding with less visualized capillaries as abnormal.

Correlations between capillary density and degree of skin pigmentation in healthy children analysed by nailfold video capillaroscopy

“…To evaluate this, nailfold capillaroscopy examinations in healthy adults are first needed. Recently, a study in healthy adults was performed in India by Bairwa et al ( 27 ) In line with our results, they found that the density of capillaries visualized by nailfold capillaroscopy decreases as the skin pigmentation increases. Of note, they included 118 healthy adults with Type III, IV, V, and VI skin phototypes (classified by Standard Fitzpatrick classification of skin phototype).…”