Purpose: Identify patients who likely have carpal tunnel syndrome based on specific patient characteristics.
Rule:
1. Shaking hands for symptom relief
2. Wrist-ratio index greater than .67
3. Symptom Severity Scale score greater than 1.9
4. Reduced median sensory field of digit 1
5. Age greater than 45 years
| Item | 3+ variable | 4+ variables | 5 variables |
| SN | 0.98 | 0.77 | 0.18 |
| SP | 0.54 | 0.83 | 0.99 |
| +LR | 2.1 | 4.6 | 18.3 |
| -LR | |||
| PPV | 52% | 70% | 90% |
| NPV |
SN = sensitivity – ‘SnOut’ helps rule out a disease (higher number is better – >0.9 is excellent)
SP = Specificity – ‘SpIn’ helps rule in a disease (higher number is better – greater than 0.90 is excellent))
+LR = positive likelihood ratio – ratio of positive test results in a patients with the pathology (true positives) higher number is better (> 10 is excellent)
-LR = negative likelihood ratio – ratio of negative test results in a patients with the pathology (false negatives) lower number is better (< 0.1 is excellent)
PPV = positive predictive value – percentage of patients who both test positive & have the disease (true positives)
NPV = negative predictive value – percentage of patients who both test negative & do not have disease (true negatives)
References:
1. Wainner RS, et al. Development of a clinical prediction rule for the diagnosis of carpal tunnel syndrome. Arch Phys Med Rehabil. 2005; 86(4): 609-18.
