An improvised 10-min rapid Lowry’s protein estimation for clinical samples

Lowry’s protein estimation method is widely used with and without modifications in research field. Conventionally, the alkaline-copper-tartrate reagent has been made fresh every time and the total assay time of Lowry’s method is 30-45 min. The objectives of this study were to reduce the assay time (to 10 min) and to validate the practice of stored 5X Lowry reagent at different temperatures up to 30 days. This study was an analytical study. Standards with BSA ranging from 3 to 25 μg/well were used for optimization of assay procedure. Serum (n=25) and CSF (n=15) samples were taken for validation purposes of stored Lowry reagent. Concentrated 5X Lowry reagent (fresh or stored at 0 °C, -20 °C and -80 °C) was added. After 1N Folin or 2N Folin addition, the plates were read after 20 min or at different time points (0, 5, 15 and 20 min) respectively. Comparison of R2 value, precision of predictors (RSE), estimated proteins (Bland Altman plot), total proteins (ANOVA) in biofluids was made between experimental groups. The trendline of 1N and 2N Folin showed similar R2, among which, a linear model was achieved in the latter. The estimated protein did not significantly vary between different time points and hence 0th min was taken for further analysis. The total serum and CSF protein estimated by 5X Lowry reagent stored at 0 °C for up to 30 days were in accordance with fresh reagent. This improvised 10-min Lowry protocol for protein estimation is beneficial to both clinical and research laboratories.