Sonographic Analysis of Nails in Psoriatic Arthritis and Healthy Controls

The sonographic normal nail plate term indicates a trilaminar band of the nail plate with two hyperechoic layers separated by a hypoechoic one. The "nail plate impairment score" means the number of nails with impaired trilaminar band (plate) among the 12 nails (all hand nails and toenails). The score ranges between 0-12, with 0 indicating no plate impairments (better) and 12 reflecting the maximal prevalence of impairment (worse).

The plate thickness of each nail was measured (in millimeters) by greyscale USG, then, the sum of 12 nails evaluated (all hand nails and toenails) was calculated as "nail plate thickness score" for a participant (in millimeters). Higher scores were expected to mean worse outcome.

The sonographic nail bed is the dark area below the nail plate to the cortical bone. The nail bed thickness of each nail was measured (in millimeters) by greyscale USG, then, the sum of 12 nails evaluated (all hand nails and toenails) was calculated as "nail bed thickness score" (in millimeters) for a participant. Higher scores were expected to mean worse outcome.

The total nail thickness (including the plate and bed) of each nail was measured (in millimeters) by greyscale USG, then, the sum of 12 nails evaluated (all hand nails and toenails) was calculated as "nail thickness score" (in millimeters) for a participant. Higher scores were expected to mean worse outcome.

Doppler activity of the nail bed and matrix was measured by power Doppler USG. The power Doppler signal for each nail was graded from 0 to 3: 1 point for a signal in less than 25 percent of the nail bed area, 2 points for a signal 25 to 50 percent, 3 points for a confluent signal in more than 50 percent of the nail bed area, and 0 point for no signal. Then, the sum of 12 nails evaluated (all hand nails and toenails) was calculated as "Doppler activity score". The score ranges between 0-36, with 0 indicating no activity (better) and 36 reflecting the maximal activity (worse).

Patients with PsA were evaluated twice in order to assess interobserver reliability. For this purpose, another investigator experienced in musculoskeletal USG performed the ultrasonographic evaluations with the same device but separately from the one who made the first assessment. Then, the consistency between the observers was calculated for each scoring by intraclass correlation coefficient (range 0-1).

Patients with PsA were evaluated again in order to assess intraobserver reliability. For this purpose, the same rheumatologist experienced in musculoskeletal USG performed the ultrasonographic evaluations again, after 2 weeks. Then, the consistency between the observers was calculated for each scoring by intraclass correlation coefficient (range 0-1).

"Minimal Disease Activity" is used for remission criteria in patients with PsA. It is defined as 5 out of 7 of the following criteria: tender joint count ≤1, swollen joint count ≤1, PASI ≤1, patient pain visual analog score (VAS) ≤15 mm, patient global disease activity VAS ≤20 mm, health assessment questionnaire ≤0.5, and tender entheseal points ≤1

"Disease Activity index for Psoriatic Arthritis" is used for disease activity states and response criteria in patients with PsA. It is simply calculated by summing swollen + tender joint counts + VAS pain + VAS patient global assessments + C reactive protein.

"Psoriasis Area and Severity Index" is used for the measurement of severity of psoriasis. It combines the assessment of the severity of lesions and the area affected into a single score in the range 0 (no disease) to 72 (maximal disease). The body is divided into four sections: head 10 percent, arms 20 percent, trunk 30 percent, legs 40 percent. Each of these areas is scored by itself, and then the four scores are combined into the final score. For each section, the percent of area of skin involved, is estimated and then transformed into a grade from 0 to 6 (0: 0 percent of involved area, 1: < 10 percent of involved area, 2: 10-29 percent of involved area, 3: 30-49 percent of involved area, 4: 50-69 percent of involved area, 5: 70-89 percent of involved area, 6: 90-100 percent of involved area) Within each area, the severity is estimated by three clinical signs: erythema, induration and desquamation.

"Nail Psoriasis Severity Index" is used to measure the severity of inspectional nail psoriasis by area of involvement in the nail unit: Each nail is divided into four quadrants and any nail plate or bed changes found are accounted for, generating a score that varies from 1-80. Higher scores mean a worse outcome.