Adapted from Wiki: Positive Predictive Value
Condition (predetermined) 

Condition Positive  Condition Negative  
Test Outcome 
Test Outcome Positive 
True Positive  False Positive (Type I error) 
Positive predictive value = Σ True Positive Σ Test Outcome Positive

Test Outcome Negative 
False Negative (Type II error) 
True Negative  Negative predictive value = Σ True Negative Σ Test Outcome Negative


Sensitivity = Σ True Positive Σ Condition Positive

Specificity = Σ True Negative Σ Condition Negative

Patients with concussion 

Condition Positive  Condition Negative  
ImPACT Test Outcome 
Test Outcome Positive 
True Positive (TP) = 59 
False Positive (FP) = 7 
Positive predictive value
= TP / (TP + FP)
= 59 / (59 + 7) = 89.4% 
Test Outcome Negative 
False Negative (FN) = 13 
True Negative (TN) = 59 
Negative predictive value
= TN / (FN + TN)
= 59 / (13 + 59) = 81.9% 

Sensitivity
= TP / (TP + FN)
= 59 / (59 + 13) = 81.9% 
Specificity
= TN / (FP + TN)
= 59 / (7 + 59) = 89.4% 