[Pulmonary activity in sarcoidosis: 67Ga uptake quantification and plasma determination of 1,25-dihydroxyvitamin D)]

The aim of our study was to produce a quantitative determination of Ga-67 pulmonary intake and correlate it with plasma levels of calcitriol.

A prospective study was conducted, and included 65 patients (29 female, 36 male) referred to our section due to suspected sarcoidosis or fibrosis of the lungs. Gammagraphic images were obtained after injecting Ga-67 citrate, and vitamin D was determined by IRMA method. The final diagnosis led to 4 groups of patients: 26 with active sarcoidosis; 5 with inactive sarcoidosis (4 with a previous gammagraphic study, included in the previous group); 8 with fibrosis of the lungs; and 30 patients with no demonstrable pathology following medical/instrumental examination. For the quantitative analysis, areas of interest were drawn around each lung, together with another region in soft tissue of the right shoulder (background). The geometric mean for each region was calculated, as well as the Ga intake rate (InGa = [lung activity-background]/background).

Significant differences were found (p<0.01) when comparing each group's InGa, with the highest values occurring in the active sarcoidosis group. No significant differences were found when comparing plasma levels of calcitriol. No significant correlation was demonstrated between hormone and InGa rates.

InGa would seem to be a useful parameter for assessing inflammatory activity in the parenchyma of the lungs. Perhaps as a result of their variability, plasma concentrations of the active vitamin D metabolite have a limited role in this assessment.