14 samples were positive on extended incubation CDC but negative on anti-human globulin CDC, with positivity on the former ranging from 10-15%.
Comparison of anti-human globulin CDC with routine incubation CDC also showed a significant difference (p=0.
These include the anti-human globulin technique, and extended incubation (6,7).
In our study, as expected, both enhancement methods produced a significant and comparable increase in positivity over routine incubation CDC with a mean increase in reactivity of 7% for both extended incubation CDC and anti-human globulin CDC over routine incubation CDC.
The use of anti-human globulin enhances the detection of weak or low titred antibodies as well as non-complement fixing antibodies, including cytotoxicity negative adsorption positive (CYNAP) antibodies (8-11).
first introduced the anti-human globulin technique, and observed that it had higher sensitivity and enhanced the reaction as compared to extended incubation CDC.
Cross and others have demonstrated enhancement of the reaction, detection of antibody in higher dilutions, and enhanced binding of complement when using anti-human globulin even when direct CDC was positive (6,10).
This suggests that weakly bound antibodies may be lost during the wash steps in the anti-human globulin CDC technique.
This case showed strong positivity with anti-human globulin which was not evident on extended incubation CDC.
As has been previously reported, anti-human globulin CDC and extended incubation CDC enhance the positivity of the routine incubation CDC.
We also found that both anti-human globulin CDC as well as extended incubation CDC used in isolation could potentially miss some positive samples.
B) Routine incubation CDC (x axis) versus anti-human globulin CDC.