NO! That's not true. That's impossible
The measure of the ability of a test to detect a condition
Sensitivity
The measure of the ability to determine that a disease is not present.
Specificity
The probability that a positive test result represents a true positive.
Positive predictive value
The probability that a Negative test result represents a true negative.
Negative predictive value
These 2 probabilities are affected by the prevalence of the condition being tested for.
Positive and negative predictive values
The decreased likelihood of something happening based on population likelihood.
Absolute risk reduction
The number of people who have a negative test and in fact have the condition.
False negative
Number of people you need to treat to cause 1 undesired outcome.
Number needed to harm
The number of people who need to receive a treatment to prevent 1 undesired outcome.
Number needed to treat
May also see number needed to screen
The number of people who have a positive test and truly don't have the condition.
False positives
The decreased likelihood of something happening compared to the base likelihood of that thing happening.
Relative risk reduction
The number of people who have a positive test and truly have the condition.
True positives
These 2 innate measures of a test are not affect by disease prevalence.
Sensitivity and Specificty
The likelihood of something happening after an exposure relative to it happening without the exposure
Odds ratio
The number of people who have a negative test and truly don't have the condition.
True negatives
1
absolute risk reduction
Number needed to treat
TN
TN+FP
Specificity
Results of a clinical study show a relative risk reduction (RR 0.67) of 33% and an absolute risk reduction (AR = 0.8) of 20%. There are 1000 patient each in the treatment and control groups. To help determine the potential benefit of the treatment, it is necessary to identify the number needed to treat (NNT).
1/20% = 5
The negative predictive value of the following situation:
A home urine test is designed to detect a type of cancer. The gold standard for this cancer is a biopsy. The biopsy is more costly, invasive, and associated with lots of adverse side effects.
To test the effectiveness of the home urine test, 104 people took the test and then agreed to a biopsy. When the study was concluded, 77 people tested negative and 27 tested positive on the urine test. Biopsies were positive in 18 individuals, 8 of whom tested negative on the urine test.
90%
TP(FN+TN)
FN(TP+FP)
Relative risk reduction
TP
TP+FN
Sensitivity
TP/FP
FN/TN
Odds ratio
TP
TP+FP
Positive predictive value
TN
TN+FN
Negative predictive value
The specificity of the following scenario:
In a study to evaluate a test as a screen for the presence of a disease, 235 of the 250 people with the disease had a positive test and 600 of the 680 people without the disease had a negative test.
600/680
88%