Lecture 21: Home testing & Monitoring Devices Flashcards
Home diagnostic market is motivated by:
○ Increased public interest in health and preventive medicine
○ Reduced health care costs
○ Reduced access and availability of health care resources
○ Increased number of available tests
○ Important technology advances → simple, accurate tests
Regulation
● FDA requires that tests are as accurate as professional use
equivalent
● CAVEAT: Test must be used correctly
General Considerations with OTC Testing
● Ensure the product is FDA approved: www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfIVD/Search.cfm ● Check the expiration date ● Follow directions for storing ● Consider simplicity of use ● Consider cost
General Counseling Points
● Read all instructions carefully
● Make sure you have enough time and all the supplies to complete the
test
● Use an accurate timing device
● Use an area with good lighting if looking for a color change
Sensitivity
ability to correctly identify people who have the disease
○ Ability to identify TRUE POSITIVE
○ Highly sensitive = low rate of false negatives
○ A nonsensitive test would identify no one as
having the disease
Specificity
ability to correctly rule out those who do NOT have the disease
○ Ability to identify TRUE NEGATIVE
○ Highly specific = low rate of false positives
○ A nonspecific test would identify everyone
as having the disease
Sensitivity and specificity are
they are inversely related
Sensitivity and specificity are valued differently for different tests
○ What would you categorize the following - more specific or more sensitive?
■ Airport bag x-ray screeners?
○ Would you prefer a test be more sensitive or more specific if testing for….
■ COVID antigen test?
■ COVID antibody test?
■ Cancer diagnostic test?
How sensitive is the test
How many actually-pregnant women does it correctly identify as pregnant?
How specific is the test?
How many not-pregnant women does it correctly confirm as not-pregnant?
What is the false-negative rate?
How many women who were pregnant were told they weren’t
What is the false-negative rate?
How many women who weren’t actually pregnant
Pregnancy Test (review)
● Detects human chorionic gonadotropin (HCG) in urine
● May work as early as 3-4 days prior to missed period
● VERY accurate starting at day of missed period
○ If taken too early it may result in a “false negative”
● Highly specific test
○ Low rate of false positives
Pregnancy Test Counseling Points
● Most accurate result comes one week after the expected missed period
● Try to test urine sample immediately after collection
● Unless the directions say otherwise, test with first morning urine (highest
concentration)
Pregnancy Test Counseling Points
● Most accurate result comes one week after the expected missed period
● Try to test urine sample immediately after collection
● Unless the directions say otherwise, test with first morning urine (highest
concentration)
Female Fertility Tests
● Options for determining optimal timing of intercourse to promote or
discourage pregnancy
○ Tests predict ovulation/fertile period
○ Not considered a reliable means of birth control
● Basal thermometer
● Urine tests
Basal Thermometer:● Basal body temperature = BBT
○ Normal = 96.00 - 97.50* F
○ 24-48 hours after ovulation = rises to closer to 98.60*
Basal Thermometer-Instructions
○ Take temperature each morning (orally, rectally, or vaginally)
○ Plot temperatures in a graph
○ When temperatures rise → fertile time!
Basal Thermometer- What type of thermometer?
Use a basal thermometer (0.1 vs. 0.2 increments)
○ Interpreting may be difficult for some individuals
○ Digital basal thermometers are available
Urinary Hormone Test - LH Test (review)
• Designed to predict ovulation to assist in conception
• Identify surge in LH that occurs before ovulation by detecting
urinary excretion of LH
• Generally occurs 8-40 hours before ovulation
• Begin testing 2-4 days before estimated day of ovulation
• Not an effective contraception method
Male Fertility Test
● Sperm count is one factor of many that may impact male fertility
● OTC tests can measure sperm count
○ Positive test does not mean fertility! May be caused by other factors
Causes of low sperm count
○ Epididymitis
○ Hormone imbalance
○ Anabolic steroid use
SpermCheck Directions/Counseling
● Collect semen sample 2-7 days after last ejaculation
● Test within 3 hours of sample collection
● Collect semen sample via masturbation with
ejaculation into the provided cup
● Sample must sit for 20 minutes in order to thin in
consistency
● Withdraw semen sample using provided device and
add to the solution bottle
● Follow directions to mix
● Read results after 7 minutes
● Presence of line = positive test = normal levels
Fecal Occult Blood Test - Colorectal Cancer
● Colorectal cancer is the third leading cause of death in the U.S.
● Fecal occult blood tests screen for blood in stool
● These tests can be used as an ADJUNCT to other more invasive tests
● Two tests:
○ Pseudo-peroxidase based toilet test (FOBT)
○ Immunochemical based FOBT (iFOBT)
● Wide range of sensitivities and specificities in available tests
● Tests are more effective at detecting lower (vs. higher) GI abnormalities
FOBT
● Utilizes a pseudo-peroxidase reaction using a
chromagen that turns blue-green when oxidized
by hemoglobin
● Blue green = positive test
● Test relies on fecal blood from stool will be left in
the toilet bowl after a bowel movement
iFOBT
● Uses antibodies to detect human hemoglobin protein in stool
● Test reacts to part of hemoglobin protein found in red blood cells
● Stool is sampled from toilet tissue after a bowel movement
False Positives
● Other GI conditions that cause bleeding:
○ Ulcers, Crohn’s disease, colitis, diverticulitis, anal fissures, hemorrhoids
● Menstruation → wait to take the test
● Certain medications: ASA, NSAIDs, steroids, rectally administered
○ Ideally meds should be avoided for 2-3 days before
● Toilet bowl cleaners?
FOBT Patient Counseling
● Increase dietary fiber intake for several days before testing
○ Roughage may stimulate bleeding from lesions
● Perform the test on 3 consecutive bowel movements
○ Cancerous lesions may bleed intermittently
● Some prescription medications may cause bleeding; consult with a healthcare
provider before discontinuing
Toilet Test Procedure
● Remove toilet tank cleansers or deodorizers, and flush toilet twice before testing.
● Keep test pads in original foil pouch until time of testing.
● Before testing, use one test pad to perform a water quality check. Hold the pad by its corners
and drop it into the toilet bowl. If any trace of blue appears in the cross-shaped area when the
pad is placed in the toilet water, use another toilet to complete the testing. Perform this water
quality check on the second toilet as well.
● Immediately after a bowel movement, place a pad in the toilet bowl, printed side up. After 2
minutes, check for the appearance of a blue cross on the test pad (positive result).
● If color changes differ from the blue cross, discard the pad and repeat the test after the next
bowel movement.
● Repeat the test on the next two bowel movements
Stool Application Product
● After a bowel movement, wipe the anal area as normal, and retain a small amount of stool on
toilet paper.
● Unscrew cap/wand from buffer tube.
● Collect a small sample of stool onto the grooves of the buffer tube cap/wand.
● Return cap to tube and screw tightly. Shake tube for 3 seconds. Unscrew smaller clear cap at
top of tube.
● Apply 3 drops from tube to sample well.
● Read results after 5 minutes. There should be a red line at “C,” which indicates the test is working. A positive test will also have a line at “T.” Do not read results if 10 minutes has
elapsed
FOBT as a Screening Test
● Screening Recommendations
○ Start screening for colon cancer at 50 years old and screen every 5-10 years (high risk start at age 40-45)
○ USPSTF recommends FOBT, sigmoidoscopy, or colonoscopy
○ American College of Gastroenterology recommends colonoscopy (more sensitive)
○ American Cancer society recommends FOBT annually, colonoscopy every 10 years
FOBT as a Screening Test
Testing is a SCREENING method -
does not diagnose a specific disease
○ Test indicates that there is any bleeding in the GI tract
○ If positive → visit healthcare provider for full workup
