A Valley Fever test, Cocci test, or Cocci titer checks the blood to see if your dog is making antibodies against the Valley Fever fungus. If the test is positive, it means your dog has been infected with the fungus.
If the Valley Fever test is positive, the laboratory then performs a titer. The titer measures how much antibody your dog is making against the fungus. A titer is obtained by doubling dilutions of the positive blood (1:4, 1:8, 1:16, 1:32 . . .) until the test becomes negative. The titer that is reported to your veterinarian is the last positive dilution. The laboratories typically stop the titer at 1:256 and report the result as ≥1:256 if the dog's blood is still positive.
In broad terms, a higher titer is equated with more severe disease. However, some very sick animals have low titers, or even negative Valley Fever tests. For these dogs, other diagnostic tests are necessary for diagnosing the illness. X-rays, blood cell counts, biopsies, and microscopic examination of cellular specimens are a few of the tests your veterinarian may need to run.
Asymptomatic dogs (infected but not showing any illness) may also have low titers, such as 1:4 or 1:8, sometimes 1:16. The titer is helpful in diagnosing Valley Fever in sick dogs, but other tests are usually needed to confirm the diagnosis.
Titers usually reduce over time as the animal's disease heals. Dogs that start with low titers (1:4 or less than 1:4) may undergo little change in the titer. Monitoring your dog's symptoms and other tests, such as blood counts and x-rays, will be better determinants of improvement in cases with low titers.
Some dogs will remain Valley Fever positive with a low titer for life. Continued treatment and monitoring of these animals needs to be determined by your veterinarian on a case by case basis.