Diagnosis of Cat Scratch Disease

Diagnosis of Cat Scratch Disease

When a physical examination reveals swollen lymph nodes and a scratch or bite caused by a cat, the doctor may suspect cat scratch disease. A more detailed physical examination may also reveal splenomegaly.

The following are some of the diagnostic tests employed to detect CSD.

  1. Bartonella henselae Indirect Fluorescent Antibody (IFA) test is quite efficient in identifying the presence of the causative bacteria. Test sensitivity is typically quite poor(53%), but this can be effectively improved by concurrent use of both IgG and IgM testing, which are more specific.
  2. Lymph node biopsy is carried out to rule out other diseases
  3. Polymerase chain reaction (PCR) test is carried out on a lymph node sample to detect the presence of the henselae bacteria. This is, by far, the most sensitive of all the diagnostic tests
  4. Routine lab tests are not very useful as they can come up with non-specific results such as leukocytosis and increased sedimentation rate. But they can help to rule out other life -threatening diseases.
  5. Cerebrospinal fluid (CSF) test results are usually normal, but can show elevated protein levels or mild pleocytosis.
  6. Electroencephalogram (EEG) findings may show a diffuse pattern in CSD patients with encephalopathy. This, however is non-specific and resolves by itself, once patient recovers
  7. Histopathological studies such as those using Brown-Hopp tissue Gram stain or Warthin-Starry silver staining reveal small, curved, gram-negative bacilli (image below).

Foot note of pic: Warthin-Starry stained sections of lymph node of CSD affected persons showing chains and clusters of organisms.