We are using haemagglutination inhibition assays to check for IAV antibodies in our sera. For weeks our positive control and positive samples have been giving us the typical result - a "teardrop" of red blood cells when the plate is tipped.
Now all of a sudden we see the RBCs pelleting to the bottom but no "teardrop" forms? We haven't changed our virus or positive sera, we get a new batch of RBCs weekly but this has now happened two weeks in a row.
Any help would be gratefully appreciated!
The disadvantages are that HAI tests are not as sensitive as EIAs or RIAs, the actual reading of results is subjective and the reagents should be fresh or else abnormal agglutination patterns may arise which makes the reading and interpretation of the test very difficult.
Standardization of these testa might be tricky. If you´re intending to keep the methodology but with more precise results it might help to use photographic registratiion.
Incomplete haem agglutination may be observed as buttons that do not tear drop.Incomplete haem agglutination is usually due to unbalanced proportion of RBCs and Virus particles which allows partial settling of RBCs but no tear drop formation under gravity.
you may carry out a laboratory scale investigation and review the data record forms to find out possible deviations from your existing SOP
1. Freshness of virus dilutions and concentration of virus in working virus solution
2. deviations in Buffer or diluent preparation
3. delay in reading plates
4. change in lot of micro titre plates
5.Lot to lot variations in RBC preparations are inherent but the use of fresh and standardized RBC suspension is important for consistent results.
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