Fact-checked by Dr. Christine Traxler, MD
There are 6 commonly used parasite tests. By comparing all 6, there is 1 parasite test that is most accurate for diagnosing parasitic infections.
Here are the 4 things you want to look for when evaluating your parasite test:
Now we’ll go through each of the 6 tests – ranking them from worst to best:
An endoscopy/colonoscopy involves sticking a small camera down your throat or up through your colon. Your gastroenterologist can look at a live video of your colon, or your stomach and small intestine.
If your doctor spots a parasitic worm (helminth) in your intestines, then your doctor can diagnose a parasite infection.
Range of parasites:
Your doctor can only see large parasites with this method of diagnosis. Many species of parasites are microscopic and can’t be seen without magnification. Parasite eggs are a reliable way to diagnose worm infections. But eggs need need up to 1000x magnification, which is not achievable with endoscopy tests.
Accuracy:
If your doctor can visually see a parasite wriggling around in your intestines, then you definitely have a parasite infection. If the doctor misses the worm, you might have a false negative test, even for the few large parasites detectable by this test.
What does a positive test mean for you?
A positive test usually means you DO have a species of worm. Worms are only one of a much greater variety of parasites, so it doesn’t mean much in the greater span of parasite infections.
What does a negative test mean for you?
A negative test is almost meaningless. It could easily mean you DO have a parasite, but the test did not detect it.
Differentiating Old and New Infections:
Your doctor will only be able to see current infections.
Convenience:
A colonscopy/endoscopy can only be performed with special equipment in a doctors office. Additionally, patients have to undergo uncomfortable bowel prep by taking a strong laxative.
I would personally not rely on a colonoscopy or endoscopy for complete diagnosis of parasite infections. Many parasites are invisible without staining and magnification, so it won’t reliably diagnose parasites except the largest ones.
Click here to read our more in-depth analysis of the endoscopy/colonoscopy parasite test.
The blood smear tests are very important for diagnosing blood-borne parasites. With the rise of Lyme disease in the USA, Babesia is a blood parasite coinfection of Lyme disease. There are other rare USA blood parasites, but I would not bet on being infected by them…even if a blood smear can find USA blood parasites like Trypanosoma cruz (causing Chagas disease).
A blood smear parasite test may be vital if you’ve fallen ill after spending time in a place with blood borne parasites (like malaria).
Overall, the accuracy of this test is very high, but the range of parasites is too limited for it to be useful for most people reading this website [one notable exception is if Lyme disease is suspected]. Therefore I would not rate this as useful for most people. Be sure to refer to the CDC website to see if you’re travelling to a place that is endemic with blood borne parasites.
What does a positive test mean for you?
It means you DO have a parasite that shows up in the blood. Most parasites, however, DO NOT show up on a blood smear.
What does a negative test mean for you?
It doesn’t mean much. You could still have one of many parasites that can’t be detected in a blood smear.
In this test, blood is drawn (or saliva collected) and then tested for antigens and antibodies that are specific to certain parasites. While this is a relatively painless procedure, it has some serious drawbacks.
Here are the drawbacks:
Saliva has only one of several types of antibodies you make when you have an infection. This means that the quantity of antibody is less in saliva, which makes many antibody-based saliva tests far less sensitive than blood testing for antibodies to parasites. That could mean that you had or are infected by a parasite, but your saliva may not show that.
The saliva test is convenient, but it has the same limitations as the blood test. Worse still, since saliva has just one type of antibody, it may show you aren’t infected with a parasite, even if you currently are infected.
What does a positive saliva/blood serology test mean for you?
Both blood and saliva testing are good at saying you have once had an infection. They are terrible, however, at telling you if you just got infected or had an infection in the past.
What does a negative saliva/blood serology test mean for you?
Blood tests will be fairly accurate in saying you never had a parasite infection if the test is negative. Saliva tests are less accurate. On the other hand, if you got infected in the last few days, you will not have built up antibodies to fight that parasite infection, so the test can also be negative when you DO have an infection.
This test is quite amazing and can give testing results very quickly (as fast as 24 hours). Essentially the technician takes a stool sample, puts it into a machine, and it tells you which parasite DNA it has found.
According to my teacher Emma Lane of Integrative Health in the UK, PCR has a strong future in parasite testing. But, she also says that it isn’t the ideal way to test for parasites today.
There are serious drawbacks to using PCR technology in its current state:
What does a positive test mean for you?
PCR tests are very sensitive in detecting parasites, but they do not help you decide if the symptoms you have now are from the parasite the test detects. Recently treated infections will still be positive for parasite DNA.
What does a negative test mean for you?
The range of parasites detected with PCR testing is too small. A negative test does not mean you do not have a parasite the test is not able to pick up on.
Click to read in depth article about PCR parasite testing.
This test, also known as microscopy, takes some feces, processes it, concentrates it, stains it, and then places it onto a microscope slide.
The technician then looks at the feces through a microscope and visually inspects and records what parasites, and parasite eggs (called ova) they observe.
In our high tech world, this “manual” method of parasite detection seems out of place. But when it comes to real world parasite infections, this is typically the most effective and reliable test for the following reasons:
What does a positive test mean for you?
When performed correctly, a positive test means you DO have a parasite infection. The range is wide, and it can tell you about a wide range of possible infections you could have – even microscopic infections.
What does a negative test mean for you?
This is a fairly accurate test. It could miss a mild infection but, because the specimen Is concentrated, stained, and microscopically examined, the “miss rate” is very low.
While this test is by far my favorite, it can also be very misleading if the technicians are inexperienced or trained poorly. Since my teacher Emma Lane works with many people with parasite infections, she needed to find the best laboratory that would give her:
In summary, here’s how I would rate each of the tests:
Unless you’ve been travelling to a place that has malaria or other blood borne parasitic diseases, the stool test (Parasite and Ova) stool test is the best.
If the lab tech is skilled and experienced, the parasite and ova test:
Click here to learn about the best home parasite stool test kit
1. Khan MQ, Gentile N, Zhou Y, Smith BA, Thomson RB, Yen EF. An audit of inpatient stool ova and parasite (O&P) testing in a multi-hospital health system. J Community Hosp Intern Med Perspect. 2020;10(3):204-209. Published 2020 Jun 14. doi:10.1080/20009666.2020.1760422.
2. John A. Branda, Tai-Yuan David Lin, Eric S. Rosenberg, Elkan F. Halpern, Mary Jane Ferraro, A Rational Approach to the Stool Ova and Parasite Examination, Clinical Infectious Diseases, Volume 42, Issue 7, 1 April 2006, Pages 972–978, https://doi.org/10.1086/500937.
3. A Case of Parasite Invasion of the Intestinal Tract: A Missed Diagnosis in Irritable Bowel Syndrome. Clin Endosc. 2013;46 (6): 671-674.
4. Alessandra Ricciardi, Momar Ndao. Diagnosis of Parasitic Infections: What’s Going On? Journal of Biomolecular Screening, Volume: 20 issue: 1, page(s): 6-21. Article first published online: August 28, 2014.
5. Sow D, Parola P, Sylla K, et al. Performance of Real-Time Polymerase Chain Reaction Assays for the Detection of 20 Gastrointestinal Parasites in Clinical Samples from Senegal. Am J Trop Med Hyg. 2017;97(1):173-182. doi:10.4269/ajtmh.16-0781.
6. Jon E. Rosenblatt, L. Barth Reller, Melvin P. Weinstein, Laboratory Diagnosis of Infections Due to Blood and Tissue Parasites, Clinical Infectious Diseases, Volume 49, Issue 7, 1 October 2009, Pages 1103–1108, https://doi.org/10.1086/605574.
7. Ndao M. Diagnosis of parasitic diseases: old and new approaches. Interdiscip Perspect Infect Dis. 2009;2009:278246. doi:10.1155/2009/278246.
Evan Jerkunica, Parasites.org's founder is happy to help. To get your questions answered, you can:
Email Support@parasites.org