The modified Nail Psoriasis Severity Index: validation of an instrument to assess psoriatic nail involvement in patients with psoriatic arthritis.
OBJECTIVE
Patients with psoriasis and psoriatic arthritis (PsA) commonly have nail involvement. There is no validated psoriatic nail assessment tool. Recently, investigators developed the Nail Psoriasis Severity Index (NAPSI). Beginning with NAPSI, our goal was to validate a psoriatic nail assessment tool for use in clinical trials, and investigate correlations between nail and other PsA features.


METHODS
Fingernails of 29 patients with PsA were photographed and scored. Clinical data were collected. Using the original NAPSI, analysis revealed high interrater variability of nail scores. Twenty patients' photographs were regraded using the modified NAPSI (mNAPSI).


RESULTS
The mNAPSI scores had excellent interrater reliability (Cronbach's alpha 0.98). Nail scores and physicians' global nail severity visual analog scores showed good inter- and intrarater correlations (Spearman's rho 0.85 and 0.90-0.99, respectively; p < 0.01). Several clinical measures correlated with nail scores.


CONCLUSIONS
The mNAPSI demonstrated excellent interrater reliability and construct validity, and may be a valuable tool.
Cassell
Sarah E
SE
Division of Rheumatology, Allergy and Immunology, University of California, San Diego, San Diego, California, USA.
Bieber
Jeffry D
JD
Rich
Phoebe
P
Tutuncu
Zuhre N
ZN
Lee
Susan J
SJ
Kalunian
Kenneth C
KC
Wu
Christopher W
CW
Kavanaugh
Arthur
A
D000328:Adult; D000368:Aged; D015535:Arthritis, Psoriatic / Q000150:complications* / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009260:Nail Diseases / Q000209:etiology* / Q000473:pathology*; D015588:Observer Variation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index