Citation:
Primary guides:
Was there an independent, blind comparison with a reference standard?
Did interpreters assess independently?
Were they blinded?
Gold standard = ____________________________________________
Did the patient sample include an appropriate spectrum of patients to whom the diagnostic test will be applied in clinical practice?
Did they include those with a mild form of the disease?
Did they include those with different but potentially confused disorders? Which ones?
Secondary guides:
Did the results of the test being evaluated influence the decision to perform the reference standard?
Is there verification bias (also called workup bias)? In other words, do the results influence whether patients undergo confirmation with the gold standard?
Were the methods for performing the test described in sufficient detail to permit replication ?
Do they tell you how to:
Q prepare the patient (diet, drugs to avoid, precautions after test)?
Q perform the test (technique, possibility of pain)?
Q store/transport the specimen?
Q analyze and interpret the results?

Results can be presented as Sensitivity, Specificity or as Likelihood ratios (positive or negative). Are the results reported in one of these formats, or are the data available for you to perform the calculation?
If LR not given : form a 2 x 2 table sensitivity = True Positive Rate (TPR)
= a/(a+c)=_______ specificity = True Negative Rate
=d/(b+d) = _______
False Negative Rate (FNR)
FNR = 1-TPR =_______
False Positive Rate (FPR)
FPR = 1-TNR =_______
LR(+) = TPR/FPR = ________
TEST (+)
(-) gold
(+) a c standard
(-) b d
Positive Predictive Value
(PPV)
PPV= TPR/(TPR+FPR)
= _____________
NPV= TNR/(TNR+FNR)
= _____________
To use LR, one must convert probability into Odds. To do this decide what the pretest probability is (let's say it's 20%). Visualize a stick that represents the probability of disease:
20% 80%
So the odds are 20:80, or 1:4. Take all the LR's from the data and multiply it times the left hand value: LR x 1 : 4 (let's say the LR is 8.7), that'd be 8.7 x 1 : 4 resulting in post test odds of 8.7 : 4. To convert this back to probability take the part that's the odds of having disease divided by the total amount of odds, or 8.7 / (8.7+4) = 8.7 / 12.7 = 69%.

An alternative to converting to odds is to use the following nomogram.
Starting with a pretest probability of 50%, the line drawn through the LR of 4 gives you a posttest probability of 80%.
Most of us have a program on our PDA which can perform the above operation for you. All you have to have is a pre-test probability and a likelihood ratio.
Will the reproducibility of the test result (precision) and its interpretation be satisfactory in my setting?
Is the test reagent-dependent, variable amongst laboratories, or technician-dependent?
Is there inter-observer agreement?
Are the results applicable to my patient?
What is the study site?
What are the inclusion criteria?
What are the exclusion criteria?
Were the diseased and non-diseased patients similar with respect to factors unrelated to disease that may affect test results (e.g. age, sex, diet, mobility)?
Will the results change my management?
At what level of suspicion would you treat the patient? Does the posttest probability surpass this level?

Will patients be better off as a result of the test?
Was the "utility" of the test determined?
Is the target disorder, if undiagnosed, dangerous?
Does the test have acceptable risks?
Is there treatment available?
What happens to patients with true positive results?
What happens to those with false positive results? with false negative results?
What are the consequences if the test causes a delay in therapy?