Platelet derived growth factor : a potential indicator of pulmonary affection in systemic sclerosis

الملخص EN

Aim of study: To determine serum levels of platelet-derived growth factor (PDGF A/B) in systemic sclerosis (SSc) patients and to correlate these levels with the extent of skin sclerosis and the presence of pulmonary affection.

Moreover, the efficiency of PDGF and skin score in early detection of pulmonary affection was assessed.

Patients & Methods: The study included 22 female SSc patients (diagnosed according to the American College Of Rheumatology criteria) and 15 age-matched healthy control females.

The extent of skin sclerosis was assessed with the total skin score.

According to LeRoy et al.

(1988), there were 10 patients (45.5%) with localized SSc and 12 patients (54.5%) with diffuse SSc.

In our study patients with localized SSc had a skin score <25% while those with diffuse SSc had skin score >25%.

Five diffuse SSc patients had associated pulmonary affection diagnosed by full history taking, clinical examination, chest x-ray, arterial blood gases, spirometry and the diffusing capacity of the lung for carbon monoxide (DLCO).

Serum levels of PDGF were determined in SSc patients and healthy controls using the quantitative sandwich ELISA technique.

Results: Serum PDGF mean and standard deviation in healthy subjects was 5.2+2.466 ng/ml.

PDGF values showed a continuous significant increment with progression of the disease.

The mean PDGF serum levels in localized SSc, diffuse SSc without pulmonary affection and with pulmonary affection were 15.8+2.3, 20.86+2.41 and 32+3.08 ng/ml, respectively.

Furthermore, the results revealed that PDGF value <10 ng/ml tend to exclude the diagnosis of SSc with 100% sensitivity and specificity, respectively.

Moreover, all patients with diffuse SSc and having pulmonary affection had PDGF values >25ng/ml.

This value provided a diagnostic sensitivity and specificity of 100 %, respectively.

As regards the total skin score, it did not show a statistical significant difference between SSc patients with (32.2+4.49%) and without (29.71+3.25%) pulmonary affection (p>0.05).

However, in patients with diffuse SSc, PDGF levels tended to correlate positively with the skin score (p=0.05).

ROC plot showed that skin score at a value of 29% was the best cut-off level to diagnose pulmonary affection in diffuse SSc patients with a diagnostic sensitivity of 80% and specificity of 71.4%.

Conclusion: PDGF is a simple and easy laboratory test that tends to exclude the presence of SSc at a cut-off value of 10 ng/ml with 100% sensitivity and specificity.

Similarly, it highly suggests the presence of pulmonary affection in patients with diffuse SSc at a cut-off level of 25 ng/ml with a diagnostic sensitivity and specificity of 100%.

However, further studies are recommended on a larger population of patients to ensure the diagnostic efficiency of PDGF and to test the applicability of our obtained cut-off values.