Lab Medicine Flashcards
Accuracy
how closely the test results correspond to the true value or “gold standard.”
Precision
How reproduce-able the results are with repeat testing of the same specimen
Specificity
measures TN–> the percentage of persons WITHOUT the disease of interest with negative test results–>higher specificity of the test, the more likely it is that persons without the disease of interest will be excluded from consideration of having the disease
What kind of test is used to clinically rule IN the disease?
Specificity (SPIN)
T/F: The lower the specificity, the higher the chance of a false positive result
TRUE
Sensitivity
measures TP –> higher the sensitivity, the more likely to detect people WITH the dz
What is used to clinically to rule OUT the presence of the disease in an individual
Sensitivity (SNOUT)
Predictive value
Measures concerning to estimation of the probability of the presence or absence of disease.
Positive PV
percent of persons with a positive test result who DO HAVE the disease in question
Negative PV
percentage of persons with a negative test result who DO NOT HAVE the disease in question
False positive
lab testing that identifies abnormalities that are NOT present.
False negative
lab testing that fails to identify abnormalities that ARE present.
Prevalence
the proportion of a population found to have a condition (typically a disease or risk factor) at a particular time.
Likelihood Ratio
Probability of a result in a patient with or without disease
Negative LR
Probability of negative test in non-diseased person/ Probability of negative test in a diseased person
Pretest probability
the probability of the target disorder before a diagnostic test result is `known
Posttest probability
the probability of the presence of a condition (disease) after a diagnostic test.
Gold Standard
most accurate measure
Narrative result
descriptive values (ie: path report/ Chest Xray report)
five major reasons for ordering a laboratory measurement
1) Discover occult (not accompanied by readily discernible signs or symptoms) disease or recurrent disease
2) Confirm a suspected diagnosis
3) Differentiate among possible diagnoses
4) Determine the stage, activity, or severity of disease
5) Assess and monitor the effectiveness of therapy or treatment
Qualitative result
Yes/No or Positive/Negative (ie: pregnancy test, rapid strep)
Quantitative
Numerical
Reference Interval
range of “normal” values
T/F: 1 in 20 “normal” tests will have test results outside of the reference range.
TRUE
Basic Metabolic Profile (BMP):
common serum electrolytes (Na+, K+, Cl-), carbon dioxide content, blood urea nitrogen, Ca++, creatinine, and glucose
Complete Metabolic Profile (CMP):
all BMP components plus albumin, alanine aminotransferease (ALT), aspartate aminotransferease (AST), total bilirubin, and total protein
erythrocyte sedimentation test
non-specific test; increases in ESR (erythrocyte sedimentation rate) = infection, inflammation, and plasma cell dyscrasias
spun hematocrit
percentage volume of blood that is composed of erythrocytes (RBCs)
STAT laboratory tests
needed immediately; given highest priority
pinworm prep
Test for the presence of pinworm eggs on the anus
Firmly press the sticky side of a strip of tape over the anal area for a few seconds. The eggs stick to the tape. The tape is then transferred to a glass slide, sticky side down, where it can be examined
dipstick urinalysis
tests urine for protein; pH; specific gravity; bilirubin, bile, and urobilinogen; blood and hemoglobin; leukocyte esterase; nitrite; glucose; and ketones
fecal occult blood testing (FOBT):
simple screening test, detects presence of blood in stool
common sources of error that can affect the quality and variation of laboratory tests
patient variables (ie: BMI, age, gender, meds, pregnant, smoker, etc)
speciment collection variables (ie: posture, time of collection, fastings, presence of IV, etc)
specimen handling variables (ie: sunlight, temp, evaporation, hemolysis, lipemia, etc).
urine pregnancy test
detects the presence of a hormone called human chorionic gonadotropin (hCG) in urine
wet mount
vaginal discharge is placed on a slide in a salt solution to help detect the cause of vaginitis or vulvitis. The slide is looked at under a microscope for bacteria, yeast cells, trichomoniasis (trichomonads), white blood cells that show an infection, or clue cells that show bacterial vaginosis.
potassium hydroxide (KOH) mount
tests for yeast infection – A sample of the vaginal discharge is placed on a slide and mixed with a solution of potassium hydroxide (KOH). The KOH kills bacteria and cells from the vagina, leaving only yeast for easier detection of a yeast infection
capillary blood glucose (CBG):
measures blood glucose level, performed by piercing the skin (typically, on the finger) to draw blood, then applying the blood to a chemically active disposable test-strip.
ovulation test
helps determine expected ovulation by picking up the luteinizing hormone (LH), LH is always present in urine and increases 24-48 hours prior to ovulation
what is the strongest predictor of risk?
age
