Over a two week period, the reactions of your QC antibody show a gradual decrease from 2+ to a very weak positive with your antibody detection cells (screening cells). These results most likely indicate

Over a two week period, the reactions of your QC antibody show a gradual decrease from 2+ to a very weak positive with your antibody detection cells (screening cells). These results most likely indicate

• A. Deterioration of QC antibody
• B. Contamination
• C. Instrument calibration
• D. Increased antibody titer

Answer: (A)

Antibody potency and stability over time is being tested. A QC antibody should keep a consistent level of reactivity in the screening cell assay, so a gradual drop from a strong reaction to a very weak one over days to weeks indicates loss of antibody activity, i.e., deterioration. Contamination would more likely cause inconsistent or unexpected results rather than a steady, monotonic decline. Instrument calibration issues would affect many tests and produce a broader shift, not a specific decline in this QC antibody’s reactivity. An increased antibody titer would yield stronger, not weaker, reactions. So the pattern most aligns with deterioration of the QC antibody.

Antibody potency and stability over time is being tested. A QC antibody should keep a consistent level of reactivity in the screening cell assay, so a gradual drop from a strong reaction to a very weak one over days to weeks indicates loss of antibody activity, i.e., deterioration. Contamination would more likely cause inconsistent or unexpected results rather than a steady, monotonic decline. Instrument calibration issues would affect many tests and produce a broader shift, not a specific decline in this QC antibody’s reactivity. An increased antibody titer would yield stronger, not weaker, reactions. So the pattern most aligns with deterioration of the QC antibody.