“Fit test” refers to two very different procedures depending on the context: a fecal immunochemical test (FIT) used to screen for colorectal cancer at home, or a respirator fit test required by workplaces to ensure a mask seals properly against your face. Both are straightforward, but each has specific steps that matter for getting an accurate result. Here’s how to do both correctly.
The Fecal Immunochemical Test (FIT)
A FIT is a home stool test that detects tiny amounts of blood in your stool, which can be an early sign of colorectal cancer or precancerous growths. It’s one of the simplest cancer screening tools available: no fasting, no dietary restrictions, no changes to your medications, and no prep liquids or pills. You collect a small sample at home and send it to a lab.
With a single use, FIT picks up about 80% of colorectal cancers. It’s less sensitive for precancerous growths, catching roughly 20% to 30% of advanced cases, which is why repeating it annually matters. A positive result doesn’t mean you have cancer. It means blood was detected, and you’ll need a colonoscopy to find the source.
Step-by-Step Collection
Kits vary slightly by brand, but most follow the same basic process:
- Flush the toilet before your bowel movement so the bowl is clean.
- Set aside used toilet paper in the waste bag provided with the kit. Don’t drop it into the bowl, as it can contaminate the sample.
- Use the brush from the kit to lightly brush the surface of the stool.
- Touch the brush to the indicated spot on the test card.
- Dispose of the brush in the waste bag and throw it away.
- Send the sample to the lab using the provided materials.
Your provider may ask you to test more than one bowel movement before sending the kit in. Follow whatever the instructions specify for your particular kit.
Storing and Returning Your Sample
Timing matters once you’ve collected your sample. Most institutions ask you to return the specimen within seven days of collection, though many kit manufacturers rate samples as stable at room temperature for up to 15 days. Stick with the shorter window when possible. Keep the sample at room temperature (not in the freezer or a hot car) until you return it.
The most common reason labs reject a FIT sample is inadequate specimen, accounting for about 51% of unsatisfactory results. Incomplete labeling causes another 27%, and old specimens account for 13%. A small number are rejected because of broken or leaking containers. So collect enough material, fill out every label on the kit, return it promptly, and handle it carefully.
What Happens After a Positive Result
A positive FIT means blood was detected in your stool. The test can’t tell you why. The next step is a colonoscopy, which lets a doctor visually inspect the colon and remove any polyps found during the procedure. Research from the National Cancer Institute confirms that following up a positive FIT with a colonoscopy significantly reduces the risk of dying from colorectal cancer. If your result is negative, you’ll typically repeat the FIT in one year.
Respirator Fit Testing
A respirator fit test confirms that a specific mask model and size creates a proper seal against your face. OSHA requires an annual fit test for any tight-sealing respirator used in the workplace, and the test must be repeated if you switch to a different respirator model or size, or if changes to your face (significant weight change, dental work, facial surgery) could affect the seal.
There are two types: qualitative and quantitative. Both use the same set of physical exercises, but they measure the seal differently.
Qualitative Fit Testing
A qualitative test is a pass/fail method. You wear the respirator inside a hood or enclosure while a test agent is introduced. If you can taste, smell, or feel the agent, the mask is leaking. Four test agents are accepted:
- Isoamyl acetate: a liquid with a banana-like smell. You pass if you can’t detect the odor.
- Saccharin solution: a sweet-tasting aerosol. You pass if you can’t taste the sweetness.
- Bitrex: an intensely bitter aerosol. You pass if you can’t taste the bitterness.
- Irritant smoke: a chemical smoke that triggers coughing or irritation. You pass if you don’t react.
Before the actual test, the administrator runs a sensitivity check with the agent to confirm you can detect it without the respirator on. If you can’t taste saccharin under normal conditions, for example, that agent won’t work for your test.
Quantitative Fit Testing
A quantitative test uses a machine that measures the actual amount of leakage around the face seal, producing a numerical score called a fit factor. A probe is inserted through the respirator, and the instrument compares particle concentrations inside and outside the mask. This method gives a precise measurement rather than a simple pass/fail, and it’s required for certain higher-protection respirators.
The Seven Test Exercises
Whether your test is qualitative or quantitative, you’ll perform a series of exercises while wearing the respirator. Each exercise lasts one minute and simulates movements you’d make during actual work. Once the exercises begin, you cannot adjust the mask. Any adjustment voids the test and you start over.
- Normal breathing: Stand still and breathe normally without talking.
- Deep breathing: Breathe slowly and deeply while standing. Avoid hyperventilating.
- Turning head side to side: Slowly rotate your head to each extreme, pausing to inhale at each side.
- Moving head up and down: Slowly look up toward the ceiling and then down. Inhale when looking up.
- Talking: Speak out loud, clearly enough for the test conductor to hear. You may be asked to read a passage, count backward from 100, or recite something memorized.
- Bending over: Bend at the waist as if touching your toes. If the test setup doesn’t allow bending, jogging in place is substituted.
- Normal breathing again: Repeat the first exercise to finish the test.
Quantitative tests add one extra step: a grimace exercise where you smile or frown to briefly break the seal, then let the respirator reseat itself. This step is skipped in qualitative testing.
Seal Checks Are Not Fit Tests
A user seal check is something you do every time you put on your respirator. You cover the filter area and inhale (negative pressure check) or exhale (positive pressure check) to feel whether air is leaking around the edges. This is a quick personal check, not a substitute for a formal fit test. NIOSH is explicit that seal checks lack the sensitivity and specificity to replace either qualitative or quantitative fit testing. You should only wear a respirator model that has passed a formal fit test within the past year, and then perform a seal check each time you don it.