. 2019 Jul 9;10:829. doi: 10.3389/fphys.2019.00829

TABLE 1.

A summary of the steps involved in calculating the post-test probability of an injury occurring given a history of injury.

Step	Statistic	Value	Calculation	Description
1. Pre-test	Odds (as a decimal)	0.25	$\frac{T P + F N}{F P + T N}$	The decimal odds of sustaining a future injury for all athletes, prior to accounting for previous injury. This can also be calculated using the pre-test probability (see section “Pre-test and Post-test Probabilities”).
	Odds (as a ratio)	1:4	As above, calculated as a fraction	The likelihood of a future injury occurring (1) compared to the likelihood of a future injury not occurring (4) for all athletes.
	Probability	20%	$\frac{T P + F N}{T P + F P + F N + T N} \times 100$	The percentage of athletes likely to sustain a future injury (prior to accounting for previous injury).
	Explanation	2 in 10 chance	−	This can simplified to a 1 in 5 chance.
2. Likelihood ratio	Positive likelihood ratio	6	$\frac{S e n s i t i v i t y}{1 - s p e c i f i c i t y}$	The magnitude by which having a previous injury increases the odds of sustaining a future injury. This is calculated using sensitivity and specificity (see section “Sensitivity and Specificity”).
3. Post-test	Odds (as a decimal)	1.5	Pre−testodds×positivelikelihoodratio	The decimal odds of athletes with a previous injury sustaining a future injury.
	Odds (as a ratio)	6:4	As above, calculated as a fraction	The likelihood of a future injury occurring (6) compared to the likelihood of a future injury not occurring (4) for athletes with a previous injury.
	Probability	60%	$\frac{P o s t - t e s t o d d s}{P o s t - t e s t o d d s + 1} \times 100$	The percentage of previously injured athletes likely to sustain a future injury. This is calculated using the post-test odds.
	Explanation	6 in 10 chance	−	This can be simplified to a 3 in 5 chance.

The derived values have been calculated using the example and mock dataset illustrated in Figure 2. For a detailed outline of the steps involved, see section “Pre-test and Post-test Probabilities.” TP, true positive; TN, true negative; FP, false positive; FN, false negative.