Occult Heartworm Test Information

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Occult Heartworm Test Information

Test Code: OH
Test Name: Occult Heartworm Test

Contact Name: Dr. Mani Lejeune
Contact Telephone: 607-253-3581
E-mail: ml872@cornell.edu

Test Method: Antigen capture enzyme-linked immunosorbent assay
Sample Required: 1 ml of serum or plasma
Collection container: red-top tube
Transport: Ship on cold packs
Test Day: Tuesday and Friday
Lag Time: 1-7 days
Species: Dog and Cat
Results Format: Positive or Negative


The Synbiotics DiroCHEK heartworm test is an indirect enzyme-linked immunosorbent assay (ELISA) used for the detection of adult female Dirofilaria immitis antigen in canine and feline serum or plasma. This test is validated for use in dogs and cats only. Other animals may be tested by this method, but reactivity in other species is not clearly defined. This test method can be used to detect Dirofilaria immitis five to six months after infection in dogs, and seven to eight months after infection in cats. Because of the nature of this disease in cats, veterinarians may want to consider including feline heartworm antibody testing for a more accurate assessment of a cat’s true infection status.

Results of the DiroCHEK test may be interpreted as follows:

Antigen Positive

  • single sex infection (female)
  • immature adult worms (5-6 months postinfection)
  • immune mediated clearance of microfilariae

Antigen Negative

  • heartworm antigen not present, or present in levels too low to detect
  • adult worms dead and antigen cleared, but microfilariae still present
  • immune mediated clearance of antigen-antibody complexes
  • antigen destroyed due to improper storage or treatment of sample