N-NAIL Score Demonstrates Greater Accuracy than NAPSI in Diagnosing Nail Psoriasis

Recent research published in the International Journal of Dermatology highlights the superior diagnostic performance of the Nijmegen-Nail Psoriasis Activity Index Tool (N-NAIL) compared to the Nail Psoriasis Severity Index (NAPSI) for identifying nail psoriasis. Both scoring systems are used to evaluate the severity of nail involvement in psoriasis patients, but findings show that N-NAIL offers improved accuracy and simplicity.

The study, led by Dr. Evi C.C. Rikken from Radboud University Medical Center in Nijmegen, involved a cohort of 104 patients with psoriasis, of whom 68 had confirmed nail psoriasis. Researchers established optimal cutoff points for each scoring tool to determine their diagnostic efficacy. The N-NAIL, with a cutoff value of 2, achieved a sensitivity of 83.8% and specificity of 83.3% in diagnosing nail psoriasis among the psoriasis population. Similarly, in the general population, this cutoff maintained high sensitivity (83.8%) but a slightly lower specificity (67.3%).

In comparison, the NAPSI showed its best performance at a cutoff of 7 for patients with psoriasis, with a sensitivity of 80.9% and specificity of 69.4%. In the broader population, a cutoff of 10 was optimal, yielding a sensitivity of 72.1% and specificity of 70.2%.

The authors emphasized that the N-NAIL’s streamlined single-version scoring system makes it easier and quicker for dermatologists and researchers to apply, reducing confusion and facilitating more efficient diagnosis. The study underlines that the N-NAIL's higher accuracy and ease of use make it a preferable choice over NAPSI for clinical and research purposes.

For more details, refer to the original study: Evi C. C. Rikken et al., "What Is the Diagnostic Capacity of Existing Severity Scoring Tools for Nail Psoriasis?", International Journal of Dermatology (2025). [DOI: 10.1111/ijd.70024]

Source: https://medicalxpress.com/news/2025-08-score-accurate-napsi-psoriasis.html