Positive Likelihood Ratio Calculator
Calculates the positive likelihood ratio for a diagnostic result. The form displays sensitivity/(1−specificity) beside positive likelihood ratio, using a worked condition that can be recalculated with the labeled inputs.
Set the labeled inputs
Positive Likelihood Ratio
Scope of the positive likelihood ratio method
The positive likelihood ratio page calculates the positive likelihood ratio for a diagnostic result.
Positive Likelihood Ratio is limited to the statistical quantity named by the result panel. The positive likelihood ratio calculation does not silently add a population, time horizon, causal direction, or decision threshold that is absent from the fields.
Before entering the positive likelihood ratio data
- True positives: For positive likelihood ratio, the worked value for true positives is 80 cases. Treat the true positives entry (80 cases) explicitly as a count, proportion, rate, estimate, or model parameter before comparing positive likelihood ratio conditions. The form enforces minimum 0.
- False negatives: For positive likelihood ratio, the worked value for false negatives is 20 cases. Treat the false negatives entry (20 cases) explicitly as a count, proportion, rate, estimate, or model parameter before comparing positive likelihood ratio conditions. The form enforces minimum 0.
- False positives: For positive likelihood ratio, the worked value for false positives is 10 cases. Treat the false positives entry (10 cases) explicitly as a count, proportion, rate, estimate, or model parameter before comparing positive likelihood ratio conditions. The form enforces minimum 0.
- True negatives: For positive likelihood ratio, the worked value for true negatives is 90 cases. Treat the true negatives entry (90 cases) explicitly as a count, proportion, rate, estimate, or model parameter before comparing positive likelihood ratio conditions. The form enforces minimum 0.
The entries used for positive likelihood ratio must refer to one coherent analysis condition. Combining incompatible populations, periods, or measurement definitions can produce valid positive likelihood ratio arithmetic for a nonexistent study.
The surrounding workflow may also require negative likelihood ratio.
From inputs to positive likelihood ratio
For positive likelihood ratio, match every symbol in the relationship to a labeled field before substituting numbers. Positive Likelihood Ratio is reported in the scale implied by the inputs and formula.
While checking positive likelihood ratio, inspect every denominator in sensitivity/(1−specificity). For positive likelihood ratio, a zero or near-zero denominator can make positive likelihood ratio undefined or unstable.
A fixed case for comparison
The default positive likelihood ratio condition is True positives = 80 cases, False negatives = 20 cases, False positives = 10 cases, True negatives = 90 cases.
Sensitivity .80 and specificity .90 give a positive likelihood ratio of 8.
The live calculator reports Positive likelihood ratio 8. Repeating one intermediate step from sensitivity/(1−specificity) provides a fixed positive likelihood ratio reference check for later code changes.
Statistical context for positive likelihood ratio
Likelihood ratios update odds; they are not probabilities of disease by themselves.
For positive likelihood ratio, diagnostic and risk measures are conditional on named denominators, reference definitions, population prevalence, and follow-up time.
A second check on positive likelihood ratio
When interpreting positive likelihood ratio, keep the two-by-two counts or source risks with the result; a ratio alone can hide very different absolute event frequencies.
As a second check for positive likelihood ratio, reversing the numerator and denominator answers a different question, so retain the direction printed in sensitivity/(1−specificity).
Varying a single positive likelihood ratio input at a time
Change true positives while holding the remaining entries fixed, then state why the direction and size of the positive likelihood ratio change are plausible from sensitivity/(1−specificity).
Repeat the positive likelihood ratio exercise with true negatives. If a modest defensible change materially alters the interpretation, report both conditions rather than presenting that positive likelihood ratio scenario as exact.
Input and rounding traps
Before accepting positive likelihood ratio, compare every entered value with its label, unit, and allowed domain after reading the printed relationship from left to right.
For positive likelihood ratio, do not move a number between fields merely because the units look compatible; each label gives the number a different statistical role.
Another positive likelihood ratio failure occurs when a rounded output is reused as though it were the original measurement. Carry guard digits through calculations that depend on positive likelihood ratio, then round only the reported value.
Documenting the positive likelihood ratio result
Report positive likelihood ratio using sensitivity/(1−specificity), followed by the entered values, units, exclusions, and analysis date. Name the positive likelihood ratio population or dataset boundary instead of leaving it implicit.
Keep the full calculator output with the record, including Positive likelihood ratio 8. A later positive likelihood ratio review can then distinguish a changed input from a different convention or software implementation.
Questions about positive likelihood ratio
Why could another program report a different positive likelihood ratio?
A different convention for rounding, tails, ties, interpolation, parameterization, or missing values can change positive likelihood ratio. Compare the printed positive likelihood ratio formula and its input definitions before treating either output as wrong.
What does positive likelihood ratio represent on this page?
It is the quantity produced by sensitivity/(1−specificity) from the displayed true positives, false negatives, false positives, true negatives. This page calculates the positive likelihood ratio for a diagnostic result.