Abstract #2 : Skin Thickness Progression Rate in Systemic Sclerosis with Diffuse Cutaneous Involvement: A Predictor of Outcome
Authors:
Robyn T. Domsic, Tatiana S. Rodriguez-Reyna, Noreen Fertig, Mary Lucas, Molly T. Vogt, Thomas A. Medsger, Jr.
Background
This study examined the rate of skin thickness progression as a predictor of poor outcome in patients with diffuse scleroderma in the University of Pittsburgh database.
Methods:
The Skin Thickness Progression Rate (STPR) is defined as the modified Rodnan skin score at first visit/duration of skin thickening by patient report. Criteria for inclusion were first evaluation between 1980 and 2004, diffuse skin involvement at first visit, less than 2 years of skin thickening by history, antibodies positive to a scleroderma-specific antibody (anti-topo, anti-RNA polymerase III or other). The baseline levels of STPR were divided into tertiles for analysis (<25, 25-45, >45 per year). Outcome measures of interest were development of internal organ involvement (renal crisis, interstitial lung disease, cardiac involvement) and 5 year survival. Co-variates in the model included age of onset, gender, race, antibody status and baseline skin score.
Results:
The 689 subjects were mostly Caucasian and female with a mean age of 46 years at symptom onset. The STPR was an independent predictor of organ involvement (OR of 2.03), as were male gender, age at onset and antibodies to topo. The 5 year survival for the 3 STPR groups were 82%, 81% and 72% in the <25, 25-45 and>45 groups respectively. Rapid STPR (>45) was also an independent predictor of 5 year mortality with an OR of 1.63 (1.10-2.42) as were scleroderma renal crisis, African-American race, cardiac disease and age at onset. RNA-polymerase III antibodies seemed to have a protective effect (OR 0.44, 0.29-0.66).
Editorial Comment:
This study observes that a relatively simple estimate of reported skin thickness progression is an independent predictor of bad outcomes (mortality and major organ involvement) in scleroderma. This measure does rely on patient report of skin tightness onset, but is easy to obtain and may be a valuable tool in the clinical setting to identify a subset of patients at risk. It is interesting to note that they also evaluated mRSS at first visit and did not find an association, suggesting that there may be something about the rapidity of change that is associated with outcome. Other predictors or mortality in this study have been previously shown to associate with poor outcome such as cardiac disease, renal crisis and African-American race. It was interesting to note that the presence of interstitial lung disease was not a predictor of increased mortality (since lung disease is the leading cause of mortality in scleroderma), but this may be a matter of classification. Most patients with scleroderma will have some interstitial lung disease, but only a small subset with have progressive decline in lung function. So how this was defined is key. In the future, this may be a better parameter for an inclusion criterion than an absolute value for skin thickness for clinical trials.
