There are two major methods of diagnosis for rabies. They are called reference method and the method of differential diagnosis. The two methods are based on examining the symptoms and conducting tests on the patient. However the accuracy of diagnosis depends upon the accuracy of the test results produced. The accuracy of treatment depends upon the accuracy of diagnosis. For effective diagnosis the infection or a possibility of infection has to be reported as soon as possible to the concerned medical practitioner.

The extent of diagnosis also depends upon the extent of the infection. Very mild infection may not give satisfactory test results however it may spread within days causing a setback in disease discovery. This is where the differential method of diagnosis has a leading edge over other diagnosis methods. It has the ability to pin point to even a mild trace of the virus in the blood stream.

The reference method of diagnosis makes use of the PCR or viral culture to detect the disease. Skin and brain samples are taken and then examined for the possibility of an infection. While the brain samples are taken from the dead, the skin samples are taken from those suffering from the disease too.

In this method the alternate source of diagnosis is urine, saliva and cerebrospinal fluid taken from the infected. However this test is not as effective as its latter counterpart. The basic diagnosis in this method depends upon the finding of negri bodies. Negri bodies are sharp outlined structures that are only few micro meters in length. They are found on the cytoplasm of the nerve cells if the particular person is infected by rabies. This is mainly found in the brain of the person who passed away due to rabies. The amount of negri body in the nerve cell may act as a deciding factor to detect the extent up to which the disease has infected the person. But the setback comes in this method because only 20% of the infected patients were found to have the negri body in their nerve cells. Hence 100% diagnosis cannot be ensured. If necessary the saliva of the animal necessary for the infection is also to be examined.

The differential diagnosis method is very sequential and systematic of diagnosing diseases. It clearly indicates the unknowns by method of elimination of non feasible possibilities. It depends on sheer probability. This method is used widely used by medical practitioners to diagnose a disease. This method also makes use of the technique called as "light microscopy". In this technique the samples (saliva, cerebrospinal fluid) are placed on a transparent medium and are examined under ambient and targeted light conditions. The resulting image is 1000 times bigger than the actual size and hence the constituents of the sample can be visually seen on the digital picture. The images are preliminarily captured on digital plates. This "light microscopy" costs only one tenth of the actual cost required in diagnosing the disease by traditional method.