To evaluate the interference of pre-analytic factors as storage time and temperature in pleural fluid adenosine deaminase (ADA) measurement in pleural effusions.
27 pleural effusions obtained from patients with neoplasm (20) or tuberculosis (07) were analyzed. The pleural effusions were collected into tubes containing EDTA. The ADA determination was realized 1, 3, 7, 10 and 28 days after the toracocentesis and the samples were stored at 4°C (refrigerator) or -20°C (freezer). The ADA determined immediately after the pleural collection (T1) was used as gold standart to the comparison with the results obtained from the other times. The ADA activity was determined by the modified Giusti method. Statistical analysis: The Wilcoxon test was used to compare T1 with the resuts obtained at 1, 3, 7, 10 and 28 days, for both temperatures. We used the Pearson coefficient to evaluate the correlation between T1 and the other times evaluated.
Pleural ADA from T1 was 36.45 U/L (23.2 ± 55.1). We do not observe differences statistically significant between this measurement with those obtained from 1, 3, 7, 10 and 28 days, for both temperatures (4°C or -20°C). The correlations between T1 and the other times were superior to 0.90 until the tenth day for both temperatures, with a tendency of decreasing around the 28th for the temperature of 4°C (r= 0.86) or -20°C(r=0.83).
ADA levels are stable for at least 28 days in samples of pleural fluids if they were maintained refrigerated (4°C) or freezed (20°C).
Considering that samples of pleural effusion can be sended to ADA determination many hours after the toracocentesis or that frequently we have to confirm ADA results, we consider safe to quantify this enzyme until at least 28 days after the collection, if the samples were maintained at refrigerator or freezer.
Leila Antonangelo, None.