infections
Cat Scratch Disease
Diagnosis of Cat Scratch Disease
Blood tests Sometimes blood culture Sometimes lymph node fluid aspiration or biopsy To diagnose cat-scratch disease, doctors measure antibodies to the bacteria in the blood. ( Antibodies are proteins produced by the immune system to help defend the body against a particular attacker, such as the bacteria that cause cat-scratch disease.) In very sick people or people with a weakened immune system, doctors may also take a sample of blood and send it to a laboratory to grow (culture) and identify the bacteria. Or doctors may insert a needle in an infected lymph node to remove a sample of fluid. Doctors then use the polymerase chain reaction (PCR) technique on this sample to increase the amount of the bacteria's DNA so that the bacteria can be detected quickly. If the diagnosis is unclear, particularly if cancer is suspected, doctors take a sample of tissue from a swollen lymph node and analyze it (lymph node biopsy). 