Page 343 - The Veterinary Laboratory and Field Manual 3rd Edition

312 Susan C. Cork, M. Faizal Abdul Careem and M. Sarjoon Abdul-Cader

repeated and/or an alternative test should be If samples are positive on the slide agglutination
used). test it is often advisable to determine the titre of
the response using the tube agglutination test
As with most diagnostic tests, positive and nega- (for example, for Brucellosis).
tive controls should be run with every test, or
batch of tests, performed. In this case, the posi-
tive control will be a known positive antiserum. tube agglutination
A negative control will be serum from a known
sero-negative animal. Agglutination or clumping can be visualized in
test tubes by using relatively large volumes of
suspension. Agglutination is seen as a clearing
Recording the results
of the suspension due to the aggregated clumps
+++: rough agglutination (large quanti- falling to the bottom of the tube resulting in
ties) with clear fluid cleaner supernatant. In veterinary laboratories
this test is used to titrate serum antibody lev-
++: smooth agglutination with obvious
border and the fluid a little turbid els for Brucella abortus against a standard strain
and strength of B. abortus antigen. The principles
Negative: no agglutination, comparable to of the tube agglutination tests are outlined in
the negative control. Figures 6.7a and b.

Figure 6.7(a) Tube agglutination test with doubling dilutions beginning at 1 in 5. The prozone is the ‘zone’
in which the amount of antibody present is very high and does not form a complex with the antigen pres-
ent. Agglutination appears where levels of antibody and antigen form complexes which can be readily
visualized when the concentrations are within an optimal range (see also Figure 6.7b). Source: M. Sarjoon
Abdul-Cader, University of Calgary, Canada.

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