Predictive value of serum III procollagen for diagnosis of pulmonary involvement in patients with scleroderma

High resolution computed tomography (HRCT) was recently demonstrated to be as good as open lung biopsy for the diagnosis of pulmonary involvement in patients with scleroderma. Nevertheless, in view of its price and related irradiation, HRCT cannot be recommended as a screening test. Serum III procollagen (sPIIINP) is an aminopropeptide of type III collagen, which is released during conversion into collagen by specific proteases. Increased levels of sPIIINP have been observed in patients with scleroderma. The aim of the present study was to assess the relationship between sPIIINP measurement and pulmonary involvement defined according to HRCT and pulmonary function tests (PFT) with single-breath carbon monoxide transfer capacity (TL,CO) in 28 patients suffering from scleroderma. Patients were divided into two groups for analysis, Group A comprising 16 patients without pulmonary scleroderma and Group B comprising 12 patients with pulmonary scleroderma. All patients had stable cutaneous disease and normal renal and hepatic function. The level of sPIIINP was determined by radioimmunoassay (RIA-gnost P-III-P, Prod. Nr. ODMT; Behring, Marburg, Germany). Mean +/- SD sPIIINP level in Group A was 0.85 +/- 0.21 U.mL-1. Individual values ranged 0.6-1.3 U.mL-1. Mean +/- SD sPIIINP value was 1.30 +/- 0.40 U.mL-1 in Group B and individual values ranged 0.7-1.9 U.mL-1. The difference in mean sPIIINP level between Group A and Group B was significant. Using a cut-off at 1.1 U.mL-1, sensitivity of sPIIINP was 0.66, specificity 0.94, positive predictive value 0.89, negative predictive value 0.79, false positive rate 0.06, and false negative rate 0.33. The value of sPIIINP correlated with HRCT score but not with PFT. This study confirms the relationship between sPIIINP and scleroderma with interstitial lung disease. We suggest that sPIIINP could be measured in patients with scleroderma to screen those patients requiring HRCT. Further studies are necessary to determine the value of sPIIINP in terms of prognosis and follow-up of patients under treatment.