Introduction
A clinical diagnosis is the determination of the nature of a disease from the study of the presenting signs and symptoms.

A differential diagnosis is the recognition of one disease among several presenting similar problems.

Diagnostic aids are often necessary to confirm a diagnosis. These range from simple in-house tests on blood and urine to specialist assays sent to external laboratories.

The RCVS's Guide to Professional conduct states that the practice must:

Either provide laboratory facilities or have access to one or more other laboratories which are adequately equipped to perform routine clinical pathology rapidly and effectively.

A veterinary nurse must be competent in the management of the practice laboratory and the submission of samples to external laboratories. In addition a good working knowledge of common diagnostic tests on blood, urine, faeces and skin are essential since they form an integral part of the Veterinary Nursing syllabus.

It may also be prudent to refer to Book II - Chapter 4 - Microbiology & Parasitology.

Learning Objectives
The learning objectives of this chapter are:

1. To appreciate the importance of health and safety in the practice laboratory.
2. To gain a good working knowledge of the various equipment and accessories commonly used in the practice laboratory.
3. To correctly dispatch samples to external laboratories.
4. To achieve a good knowledge of the morphology of blood cells, and the terminology commonly used to describe them.
5. To gain a good working knowledge of the procedure of blood sample collection and the various tests performed upon blood in the practice laboratory.
6. To gain a good working knowledge of the procedure of faecal sample collection and the various tests performed upon faeces in the practice laboratory.
7. To gain a good working knowledge of the procedure of urine sample collection and the various tests performed upon urine in the practice laboratory.
8. To correctly identify different types of crystals and uroliths associated with crystalluria and urolithiasis.
9. To gain a basic understanding of the procedures involved in skin examination and biopsies.

NB. Bacteriological and parasitic examination are covered in Book II - Chapter 4.