Serological Archive

When samples are received at the laboratory the first priority is to separate the sera and store them in such a manner as to facilitate the carrying out of the required tests. Some samples are submitted simply for storage, usually when a flock is being transferred from one farm or owner to another. Serum storage cards (McMullin,1982c) have many advantages when storing sera, even for a short time during which the various tests are completed (Figure 2.3).\par \par Storage of serum samples in such a manner as they can be selectively retrieved, can and should be carried out for varying periods according to the objective which it is intended to achieve :

1. For up to 1 month - to allow the person submitting the samples to receive and digest the significance of the results, leaving open the possibility of repeating some of the tests or requesting new tests.

2. For up to 1 year - This is a reasonable period to retain samples for routine purposes because the flock will have reached the end of its productive life before the samples are discarded in most circumstances.

3. For 5 years or longer - Long term storage of a sub-set of the serum archive may provide useful information with respect to long-term changes in disease patterns. If sera are to be retained in storage cards for a long periods it is important that the cards are carefully sealed to avoid gradual lyophilization of the samples.\par \par Most storage for periods longer than 24 hours will be at -20 C. If large numbers of samples are handled it is very important that sufficient freezer space, and appropriate boxes and shelving is available. For long term storage serum storage cards may be cut to the size of photographic slides and stored in plastic or metal slide trays. A well organized storage system is vital, not just to enable us to locate the required samples with a minimum of effort but also to facilitate the identification of the samples which need to be removed on a regular basis.

One key element to the archival system is the method of identification of samples (usually by a numbering system). An index must be maintained to cross-reference the sample numbers according to birds type and class, company and farm of origin, and the month and year on which the samples are taken. Such a system can be set up in a manually-recorded index book, however it is much more easily maintained and searched using a computer-based system such as that described on page 28.