The importance of good pipetting techniques for the proper measurement of CD4/CD8 for the management of patients with HIV necessitates regular assessment of pipetting techniques, accuracy and precision checks
Integrity of pipettes and good pipetting techniques are critical for accurate and reproducible results.
Pipette accuracy and precision checks should be peformed monthly and when indicated as part of troubleshooting corrective actions.
Pipetting techniques of new staff should be validated before the staff are certified to process patient samples.
Most techniques for pipette accuracy and precision checks are complex and require sophisticated analytical balances and extra laboratory space.
The Flow Cytometry Centre recommends a technique that does not require analytical balances .
The major advantage of the technique is that it does not require additional equipment and space.
Flow cytometers and pipettes already in use in the flow cytometry laboratory is all that is required.
The technique is peformed using cheap commercial low, medium and high fluorescent beads and 3 or 4 colour CD4/CD8 protocols (CDC/NIH 1998/2008 guidelines).
Pipetting technique, accuracy, precision and performance of single platform 3 and 4 colour protocols can all be assessed using this technique.
Fluorescent low, medium, and high beads are added to normal blood prepared for CD4/CD8 analysis as per CDC/NIH abbreviated 3 or 4 colour panels and analysed on a 3 or 4 colour flow cytometer.
The expected bead counts are compared to actual counts and the results are statistically analysed to aseess accuracy.
CD4 and CD8 counts of the normal blood are used to assess precision.
Pipetting technique, accuracy and precision should be checked monthly.
A simple, user friendly method that is compatible with flow cyometers currently in use at most reference and central hospitals in Zimbabwe can be easily utilized.
Provincial and district hospitals can regularly refer their pipettes to the nearest central or reference laboratory for precision and accuracy checks.
Details of the procedure and training are available from: Flow Cytometry Centre, suite 12A, 1st floor, Medical Centre, 52 Baines Avenue, Harare.
Flow cytometry centre SOP