title: Response monitoring and action limits: use of ADC numbers in understanding the operational characteristics of the Beckman ASTRA chemistry system.
abstract: The Beckman ASTRA is a microprocessor-controlled multichannel chemistry analyzer. The output of each module is available to the operator as analog-to-digital conversion (ADC) numbers, which we record during each calibration (Response Monitoring). After so studying three instruments for a total of 33 months, we have established limits for Calibrator ADC numbers that indicate possible operator action (Action Limits). These Action Limits are tighter than the microprocessor's programmed limits, and alert the operator to short- and long-term drift. These tighter limits warn of (a) impending failure of the instrument to calibrate or (b) possible inaccuracies in results for patients. We have instituted changes in preventive maintenance based on our studies of each module's operational characteristics, and have replaced electrodes that failed to meet our Response Monitoring specifications. Response Monitoring and Action Limits based upon ADC numbers have significantly enhanced our understanding of the ASTRA system and thus improved its operational efficiency and analytical reliability. Estimates of precision and accuracy (true value) were satisfactory in comparison to our prior single-channel continuous-flow and flame photometry analytical measurement systems.
mesh_terms: D001322:Autoanalysis / Q000379:methods*; D001774:Blood Chemical Analysis; D001786:Blood Glucose / Q000032:analysis; D003201:Computers; D003404:Creatinine / Q000097:blood; D004573:Electrolytes / Q000097:blood; D005949:Glucose Oxidase; D006801:Humans; D014508:Urea / Q000097:blood
chemical_list: D001786:Blood Glucose; D004573:Electrolytes; D014508:Urea; D003404:Creatinine; D005949:Glucose Oxidase