Diagnostic properties of nerve conduction tests in population-based carpal tunnel syndrome

Table 3 Diagnostic test properties of digit-wrist median-ulnar sensory latency difference (0.8 ms cutoff value for abnormal result) in population-based carpal tunnel syndrome (CTS) with the clinical diagnosis as criterion standard

Test property*	Symptomatic persons with clinically certain CTS	Asymptomatic control persons	Asymptomatic and symptomatic control persons
Sensitivity	70.2 (61.0–79.5) (n 66/94)
Specificity		81.6 (74.8–88.4)	73.7 (68.7–78.8)
		(n 102/125)	(n 216/293)
Positive predictive value (PPV)		18.7 (15.0–22.3)	16.2 (13.0–19.4)
		(n 83/445)	(n 83/551)
Negative predictive value (NPV)		97.9 (97.2–98.6)	98.0 (97.4–98.7)
		(n 1608/1643)	(n 1755/1790)

*shown as % (95% confidence interval), number of persons from which the rate was derived shown in italic; Sensitivity = true positives/(true positives + false negatives); Specificity = true negatives/(true negatives + false positives); PPV = true positives/(true positives + false positives); NPV = true negatives/(true negatives + false negatives); PPV and NPV were calculated based on the assumption that the same rates of disease or test abnormality found among the samples examined applied to the corresponding groups among all survey responders as described in the text and previously [8].

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