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Chronic exposure of hands to vibration is now a well described cause of Raynaud's phenomenon. According to Palmeret al , it is estimated that 220 000 cases of Raynaud's phenomenon are attributable to exposure to vibration in Great Britain.1 These epidemiological data, based on a questionnaire, are considered to be reasonably accurate.2About 4.2 million workers are exposed to hand transmitted vibration but the real impact on health and the economy is unknown.3More precise clinical data are therefore necessary before implementing a large preventive programme.
The hand-arm vibration syndrome encompasses a wide range of disorders as it is responsible for digital blanching and paraesthesias.4 Different vascular problems—such as a pure vasospastic phenomenon, a digital organic microangiopathy, or an occlusive arterial thrombosis—can be found. A diffuse vibration neuropathy with involvement of mechanical skin receptors or carpal tunnel syndrome are also often associated.5 The relation between these neurovascular disorders is not clear but autonomic dysfunction in carpal tunnel syndrome can induce a Raynaud's phenomenon which is curable with surgery.6 The prognosis of these neurovascular troubles depends on the underlying problem and cannot be evaluated with a simple questionnaire. As no single test can reliably stage the vascular and neurological component, the use of a battery of tests is necessary. Digital capillaroscopy and plethysmography with nerve conduction studies are recommended as the basic tests. Cold provocation tests are effective for grading a pure vasospastic Raynaud's phenomenon but are less reliable in other forms of vibration-induced white finger, explaining why this test is not always well correlated with the vascular symptoms.7 8Doppler and duplex studies are useful to assess the severity of an occlusive arterial disease.
Workers who use hand held vibrating tools are also exposed to diverse environmental and occupational factors accounting for the wide clinical spectra of the disease. Epidemiological studies have pointed out that the prevalence of vibration induced white finger is very wide, ranging from 0%–5% in warm climates to 80%–100% in northern climates.9 In the pure vasospastic Raynaud's phenomenon, exposure to cold is probably the most important triggering factor and cold protection the most effective preventive measure. In the case of digital blanching associated with carpal tunnel syndrome, other ergonomic factors—such as repetitive forceful use of the hands—are likely to play a dominant part and a workplace ergonomic modification is indicated.10 Hypothenar hammer syndrome is often associated with digital blanching in mechanics and carpenters, who need to stop repetitive hand trauma.11 12 For digital organic microangiopathy and diffuse vibration neuropathy, exposure to vibration is the only identified factor and this has to be stopped. In consequence, a detailed and precise clinical diagnosis with objective tests is important to find the real cause of the vascular symptoms. Then the impact of exposure to vibration on health will be more precisely evaluated and prevention will be more effective.
Palmer et al reply
We are grateful to Noel for his comments. Our study was undertaken in a community sample of over 22 000 subjects who were contacted by post to assess the public health impact of exposures to hand transmitted vibration (HTV).1-1 We could not conduct detailed investigations about this, but postal questions on digital finger blanching are considered to diagnose Raynaud's phenomenon with an acceptable degree of validity, as judged by follow up medical interview.1-2 1-3 None the less, in the management of individual patients, the case for taking a more detailed clinical and occupational history and conducting a rigorous examination is well made.
We agree that it would be useful to supplement this community investigation with a more direct assessment of exposure and health effects in occupations found to be at particular risk according to our data.1-4 In some, such as professional gardeners, the risk of hand-arm vibration syndrome has been suspected, but research reports are sparse; and so the extra information would be useful in its own right, as well as serving as a further check on the validity of our findings.
We are less certain, however, about many supplementary routine clinical investigations. Our data imply that vibration induced white finger (VWF) is a common disorder in British industry. Our enquiries, which extended to numbness and tingling in the digits and upper limb (including symptoms that disturb sleep or cause difficulty with buttons), indicate that the attributable burden of sensorineural disease is also high.1-5 By contrast, centres with the expertise to conduct batteries of tests are few in Britain. Moreover, many experts regard the clinical history to represent a gold standard for VWF outside legal situations,1-6 a view reiterated at the recent international workshop on diagnosis of injuries caused by hand transmitted vibration (Southampton, 11–13 September 2000, Palmer KT, Griffin MJ, personal communication). If so, in many day to day situations, clinical assessment should be sufficient to determine clinical management, with detailed investigations reserved for medicolegal adjudication and research (where they play an important part).
The view that VWF encompasses several discrete vascular abnormalities—such as vasospasm, thrombosis, and microangiopathy—is consistent with views expressed at the Southampton workshop. Epidemiological evidence is lacking on the relative importance of these disorders in populations exposed to HTV, and on their prognostic importance; but it may help to distinguish between them if it leads to a better understanding of risk factors or if it prompts different approaches to case management. We know of no rigorous evidence—such as randomised controlled trials—which supports this. Noel correctly states that further research is appropriate. But control of vibration at source remains the current mainstay of management for exposed workers at risk of finger blanching. Our data indicate that significant exposures to HTV (A(8)>2.8 ms-2 rms) are common in British men1-6, as are relevant symptoms,1-1 1-4 1-5 and highlight the occupations and industries which may be priorities for preventive action.1-7