N-NAIL Score More Accurate Than NAPSI for Diagnosing Nail Psoriasis
Both NAPSI and N-NAIL provide accurate cutoffs, but better accuracy seen with N-NAIL, with cutoff value of 2
By Elana Gotkine (HealthDay News) | September 03, 2025
WEDNESDAY, Aug. 27, 2025 (HealthDay News) -- Both the Nail Psoriasis Severity Index (NAPSI) and the Nijmegen-Nail Psoriasis Activity Index Tool (N-NAIL) provide accurate cutoffs for diagnosing nail psoriasis, with better accuracy seen for the N-NAIL, according to a study published online Aug. 24 in the International Journal of Dermatology.
Evi C.C. Rikken, M.D., from the Radboud University Medical Center in Nijmegen, Netherlands, and colleagues conducted a cohort study among patients with psoriasis and matching controls to examine the diagnostic performance of two severity scoring tools: the NAPSI and the N-NAIL, which were used to score fingernails. Cutoff values were established to determine their diagnostic properties. Receiver operating characteristic curves were constructed; for various cutoff points, sensitivity and specificity were calculated.
A total of 104 patients with psoriasis were included, and of these patients, 68 were diagnosed with nail psoriasis. The researchers found that a cutoff value of 2 showed the best accuracy for N-NAIL in the psoriasis population (sensitivity, 83.8 percent; specificity, 83.3 percent) and in the general population (sensitivity, 83.8 percent; specificity, 67.3 percent). A cutoff value of 7 showed the best accuracy for the NAPSI in the psoriasis population (sensitivity, 80.9 percent; specificity, 69.4 percent), while in the general population, a cutoff of 10 was optimal (sensitivity, 72.1 percent; specificity, 70.2 percent).
"This study shows better accuracy for the N-NAIL, with a cutoff value of 2, for the inclusion of nail psoriasis patients in a study from a pool of plaque psoriasis patients than the NAPSI," the authors write. "Another advantage of the use of the N-NAIL as a scoring tool is that it only has one version, so no confusion exists about the utilization of the exact scoring tool, and it is easier and faster to apply for dermatologists, researchers, and other specialists working with nail psoriasis compared to other scoring systems."
Several authors disclosed ties to the pharmaceutical industry.