Original Article
Validation of the analytical performance of Lumipulse G BRAHMS procalcitonin immunoassay on low sample volume
Abstract
Background: The measurement of procalcitonin (PCT) is currently considered a cornerstone in the diagnostic approach of patients with severe bacterial infections and for monitoring antimicrobial therapy. However, since low volume samples represent a challenge for PCT measurement, this study was aimed to investigate the analytical recovery of Lumipulse G BRAHMS PCT immunoassay using serially diluted lithium-heparin plasma samples.
Methods: Fifteen fresh lithium-heparin plasma samples were arbitrarily selected to cover clinically significant measuring ranges of PCT values (low PCT, 0.034–0.085 ng/mL; medium PCT, 0.092–0.638 ng/mL; high PCT, 2.022–9.187 ng/mL). The samples were diluted with Lumipulse sample diluent, to obtain 5 progressive dilutions (1:2; 1:5; 1:10; 1:20 and 1:32). The original samples and each serial dilution were then measured with Lumipulse G BRAHMS PCT immunoassay, and PCT data obtained on dilutions were compared to their theoretical values. An additional measurement of original plasma samples was performed with automatic 1:10 sample dilution set in the analyzer.
Results: The correlation between measured and theoretical PCT values was always excellent (i.e., r=0.999–1.000), whilst slopes and intercepts were also satisfactory. The mean recovery between theoretical and measured PCT values was ±14%, ±7% and ±1% for low, mean and high sets of samples, respectively. The mean recovery of 1:10 diluted specimens was comprised within ±20% with manual dilution and ±21% with automatic dilution for low PCT values, within ±5% with manual dilution and ±7% with automatic dilution for medium PCT values, within ±2% with manual dilution and ±1% with automatic dilution for high PCT values.
Conclusions: The results of our study suggest that measuring PCT with Lumipulse G BRAHMS immunoassay using diluted (e.g., 1:10) plasma samples is a viable option to obtained accurate data and consume a much lower volume of plasma.
Methods: Fifteen fresh lithium-heparin plasma samples were arbitrarily selected to cover clinically significant measuring ranges of PCT values (low PCT, 0.034–0.085 ng/mL; medium PCT, 0.092–0.638 ng/mL; high PCT, 2.022–9.187 ng/mL). The samples were diluted with Lumipulse sample diluent, to obtain 5 progressive dilutions (1:2; 1:5; 1:10; 1:20 and 1:32). The original samples and each serial dilution were then measured with Lumipulse G BRAHMS PCT immunoassay, and PCT data obtained on dilutions were compared to their theoretical values. An additional measurement of original plasma samples was performed with automatic 1:10 sample dilution set in the analyzer.
Results: The correlation between measured and theoretical PCT values was always excellent (i.e., r=0.999–1.000), whilst slopes and intercepts were also satisfactory. The mean recovery between theoretical and measured PCT values was ±14%, ±7% and ±1% for low, mean and high sets of samples, respectively. The mean recovery of 1:10 diluted specimens was comprised within ±20% with manual dilution and ±21% with automatic dilution for low PCT values, within ±5% with manual dilution and ±7% with automatic dilution for medium PCT values, within ±2% with manual dilution and ±1% with automatic dilution for high PCT values.
Conclusions: The results of our study suggest that measuring PCT with Lumipulse G BRAHMS immunoassay using diluted (e.g., 1:10) plasma samples is a viable option to obtained accurate data and consume a much lower volume of plasma.
