Dispatch of specimens to a reference laboratory

The peripheral laboratory sends specimens to reference laboratories or more specialized laboratories for examinations that cannot be carried out locally. For example, serological examinations for treponemal infection or typhoid; culture of stools for detection of cholera vibrio; and histological examination of biopsy material.

Table 3.2 shows, for each type of specimen and each examination:

— which container and preservative (where necessary) to use;

— how much of the specimen to send;

— how long the specimen will keep.

1. Packing specimens for dispatch 

Always observe the regulations in force in your country. 

Double pack specimens. Place the specimen in the bottle or tube and seal her- metically (fixing the stopper with sticking-plaster; see Fig. 3.73). 

Check that the bottle is labelled with the patient’s name and the date of collection of the specimen. Then place the sealed bottle in an aluminium tube with a screw cap. Wedge it in the tube with absorbent cotton wool. 

Wrap the request form around the metal tube (Fig. 3.74). It should show: 

— the patient’s name (written in capital letters) and date of birth; 

— the nature of the specimen; 

— the date of collection of the specimen;

Fig. 3.73 Packing specimens for transport

— the address of the health facility where the specimen was collected;

— the examinations required (with the physician ’s diagnosis, where appropriate).

It should also be signed by the physician.

Place the metal tube in a strong cardboard or wooden box for dispatch. Wedge the tube in tightly with non-absorbent cotton wool. Label the outside of the box: URGENT, FRAGILE and, if appropriate, INFECTIOUS MATERIAL (Fig. 3.75).

Fig. 3.74 Wrap the request form around the metal tube containing the specimen

Fig. 3.75 Label the box containing the specimen

2. Fixation and dispatch of biopsy specimens for histopathological examination 

Biopsy specimens 

To diagnose certain diseases of the organs, the physician removes a piece of tissue with forceps or a special scalpel. This piece of tissue is called a biopsy specimen. It is examined under the microscope after a thin section has been cut and treated with a special stain. 

Histopathology 

The cells of biopsy specimens from tissues and organs can be studied under the microscope. This type of examination is called histopathology and can be most important, particularly for the diagnosis of cancer. 

The laboratory technician must be able to fix the biopsy specimen and to ensure that it is properly dispatched and arrives at the pathology laboratory in a good state of preservation. 

Fixation of biopsy specimens 

The piece of tissue is immersed in a fixative fluid. This procedure should preserve the tissue in a state as close to the living state as possible, by protecting it against bacterial action, autolysis, shrinkage, etc. 

The most suitable type of bottle for biopsy specimens is a plastic-capped bottle with a wide mouth (pill bottle). Such bottles are obtainable in 60-ml, 45-ml, 30-ml and 15-ml sizes.

Fixatives 

Fixatives that are simple to prepare are: 

— formaldehyde saline (reagent no. 27); 

— Zenker fixative (reagent no. 66). Just before use, add 5 ml of glacial acetic acid per 100 ml of Zenker solution. 

Technique 

Amount of fixative 

The volume of fixative required is about 50 times the volume of the biopsy tissue. Biopsy tissue is normally 3–5 mm thick (if it is thicker, fixation is difficult or impossible). The area of the specimen, however, can vary and this is what determines the amount of fixative to be used (see Table 3.3).

Table  3.3 Calculating the  amount of fixative to use for biopsy material

Preparation 

It is essential to act quickly on receipt of a biopsy specimen. Never leave it until later. First pour the fixative into the bottle. Then pick up the biopsy specimen on a piece of stiff paper (do not use forceps, which may damage the tissue).

Drop the specimen into the bottle. 

Labelling 

Cut out a small rectangle (about 3 cm x 1 cm) of stiff paper. Using a lead pencil, write on it the name of the patient, the nature of the specimen and the date of collection. Place the slip of paper in the bottle with the fixative. 

Fixation time 

This will vary according to the fixative used.With the two fixatives mentioned above, the specimen can be left in the liquid for at least a week before it is cut and stained. Fixed material should be dispatched to the pathology laboratory without delay, but a long transit period will not result in the deterioration of specimens.

Dispatch of biopsy specimens 

Secure the cap or stopper of the bottle with adhesive plaster. Place the bottle in an aluminium tube with a screw cap, together with the request form (see section 3.7.1). Then place the tube and the request form in a small wooden or cardboard box and dispatch immediately.