The sensitivity and specificity of thermometry and plethysmography in the assessment of hand-arm vibration syndrome

Background Finger plethysmography and thermometry are objectivemeasures used to assess the vascular aspect of hand–armvibration syndrome (HAVS). Research to date shows poor correlationbetween these tests and Stockholm Workshop Scale (SWS) vascularstage. Clinicians, researchers and compensation boards requireobjective means to diagnose and quantify HAVS. Aims To define the specificity and sensitivity of thermometryand plethysmography using the SWS as the reference criterion.A secondary goal was to consider cut points for the tests optimizingsensitivity and specificity. Methods A cross-sectional analysis was conducted on HAVS patientsseen at an occupational medicine specialty clinic. Plethysmographyand thermometry were analyzed using SWS vascular stage as theoutcome variable. Logistic regression controlled for age, smokingand time since last vibration exposure and use of vasoactivemedications. The sensitivity and specificity of the combinedtests were calculated using varying cut points. Results A total of 139 patients consented to participate inthe study. Plethysmography stage 1 or greater showed the highestsensitivity (sensitivity 94% and specificity 15%). Specificitywas optimized combining plethysmography stage 3 and thermometrystage 3 (specificity 98% and sensitivity 23%). Maximal diagnosticaccuracy was achieved by plethysmography alone setting the criteriafor a positive test as being stage 1 or greater (70%). Conclusions Neither plethysmography nor thermometry either aloneor in combination demonstrated sufficient sensitivity and specificityto serve as an objective correlate for SWS vascular stage. Allcombinations of plethysmography and thermometry showed a lowerspecificity than sensitivity indicating that the SWS may beless sensitive in detecting vascular pathology than the objectivetests.