General Procedures

Quality Control Procedures

Instrumentation Quality Control

Quality control issues are of concern because of the likelihood that flow cytometric data are used to make clinical decisions, especially with respect to the medical management of human immunodeficiency virus type 1 (HIV-1) infected patients. A good quality control program is designed to assess the major instrument parameters that affect the reliability and reproducibility of data. After installation, certain components of the instrument should be tested for minimal performance. In addition, certain parameters require routine evaluation to ensure the proper functioning of the system. The efficiency and performance of optical filters, linear amplifiers, and the PMT responses should be examined. Once a reliable level of performance is established, many instrument problems can be avoided by adherence to the manufacturer's recommended maintenance schedules.

A well-designed monitoring procedure should identify both immediate and potential problems. Results of daily monitoring of instrument performance should be kept in computer logs so that trends and variations can be noted. In addition, the corrective action database is used to track and search daily problems and solutions as well as tracking service calls. For each parameter measured, tolerance limits should be established which define the acceptable range of performance. It is recommended that Levy-Jennings style charts should be used to visually inspect longitudinal data for monitoring instrument performance for precision and trends. Initial limits are derived mathematically with as few as 20 separate data points. Tolerance ranges for each parameter are defined as two standard deviations above and below the geometric mean. New ranges can be calculated periodically from the cumulative database. Tolerance limits are established for daily monitoring of optical alignment, calibration of the fluorescent intensity standard curve, and bi-weekly monitoring of electronic fluorescent compensation.

Three levels of quality control are monitored and maintained to provide an accurate determination of instrument quality assurance. These are alignment, calibration and standardization. Alignment refers to the use of latex beads (1x Rainbow beads) for optically focusing the laser and for the measurement of laser power. Calibration refers to the use of latex particles used for laser delay setting calibration (1x Rainbow beads). Standardization refers to the use of latex particles, which standardize the same fluorescent location on a daily basis. These can be used to adjust detector voltages and to determine the resolution and instrument sensitivity (1x Rainbow beads, 8x Rainbow beads and unstained COMP beads). Ultimately, these particles are linked to actual fluorochromes (e.g. FITC, PE, APC, Cy5PE, etc.) used in the instrument either on cells or on capture particles (e.g. COMP beads).

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