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Occupational Medicine Advance Access originally published online on June 16, 2006
Occupational Medicine 2006 56(6):422-425; doi:10.1093/occmed/kql044
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H. Mason, Health & Safety Laboratory. © Crown Copyright 2006. Reproduced with the permission of the Controller of Her Majesty's Stationery Office.

Modification of the Stockholm Vascular Scale

Kerry Poole, Joanne Elms and Howard Mason

Health and Safety Laboratory, Harpur Hill, Buxton, Derbyshire SK17 9JN, UK

Correspondence to: Kerry Poole, Health and Safety Laboratory, Harpur Hill, Buxton, Derbyshire SK17 9JN, UK. e-mail: kerry.poole{at}hsl.gov.uk


   Abstract
Top
 Abstract
Introduction
 Methods
 Results
 Discussion
 Conflicts of interest
 References
 
Background Staging hand–arm vibration syndrome (HAVS) depends upon accurate reporting of the extent and frequency of blanching attacks. Reporting may not be repeatable and not all individuals classifiable using the Stockholm Workshop Scale (SWS). For Department of Trade and Industry (Dti) coal miners' assessments, the SWS was modified to include a blanching score. Further modifications, which involve splitting Stage 2V into ‘early’ and ‘late’ have been proposed but the impact of this on classification has not been investigated.

Aim To investigate the impact of modifications in the SWS on HAVS classification.

Methods Staging of individuals with HAVS according to the SWS using two modified scales. Two different cut-offs for defining ‘frequent’ blanching attacks (≥3 or ≥7 attacks/week, respectively) were used.

Results One hundred and sixty-five individuals were staged. Using the SWS, 58 and 31% of the population were unclassifiable using the two cut-offs, respectively. The modification splitting Stage 2V reduced the proportions that were unclassifiable to 2 and 9%, respectively, and increased those classified as Stage 2V. The cut-off for frequent attacks used (3 or 7) affected the proportion of individuals falling into the subdivisions of Stage 2 with 17 and 42% being classified as 2Vearly and 45 and 20% as 2Vlate, respectively.

Conclusions Subdividing Stage 2V enables more individuals to be classified, but the proportion falling into each category is susceptible to the cut-off used for defining frequent attacks. Caution may need to be applied if this categorization is used to make decisions regarding fitness to work.

Keywords      HAVS; health surveillance; Stockholm Workshop; vascular


   Introduction
Top
 Abstract
 Introduction
Methods
 Results
 Discussion
 Conflicts of interest
 References
 
Exposure to hand–arm vibration can lead to a combination of neurological, vascular and musculoskeletal symptoms termed hand–arm vibration syndrome (HAVS). The sensorineural component is characterized by tingling and numbness in the affected fingers, and reduced sensitivity to temperature and vibration. The vascular component manifests itself as periodic blanching of the affected fingers provoked by cold, loss of sensitivity and painful throbbing on return of blood circulation (vibration white finger). The Health and Safety Laboratory (HSL) currently undertakes HAVS assessments within the context of health surveillance programmes.

The diagnosis of the vascular component of HAVS relies heavily upon the reporting of extent of blanching and the frequency of attacks, which may be open to misunderstanding and recall bias. A number of tests have been used to confirm the reported symptomatology but have been of limited use in confirming the vascular diagnosis or staging its severity [1–3]. The vascular symptoms have usually been staged according to the severity of reported symptoms according to the Stockholm Workshop Scale (SWS) [4,5]. Concern has been raised about the validity of this scale and the number of individuals who cannot be staged because they do not fit into one of the categories when the SWS is rigidly applied [6]. Categorization is highly dependent upon the number of attacks used to define ‘frequent’ attacks [6], though frequency of blanching episodes appears to be more related to difficulties in using the upper limb than the extent of disease [7,8]. Further clarification of the number of attacks that constitute frequent attacks is required.

A modified version of the SWS, which involves banding the extent of blanching based on the Griffin score [9] in the staging, has been used in the Department of Trade and Industry (Dti) HAVS assessments of coal miners [10] and in our HAVS assessment centre for health surveillance. However, the impact of this modification on the ability of this scale to encompass all HAVS cases has not been assessed.

More recently, a further modification to the original SWS has been proposed by Lawson at an Health & Safety Executive (HSE) expert workshop held in Manchester in October 2003 and in a subsequent HSE guidance document [11]. The main suggestion consists of splitting Stage 2V into an ‘early’ (2Ve) and ‘late’ (2Vl) category based upon the frequency of attacks and the blanching score. In this modified scheme, >3 blanching attacks/week in winter was defined as ‘frequent attacks’.

The aim of the present study was to quantify the number of individuals who could not be categorized applying the criteria for these scales and the impact of using the original and modified SWS upon the proportion of individuals falling into each staging category. Furthermore, we investigated the cut-off value for defining frequent blanching attacks and what effect changing this would have on the categorization according to the SWS. This study used data from workers referred to the HSL within the context of health surveillance programmes rather than medico-legal cases.


   Methods
Top
 Abstract
 Introduction
 Methods
Results
 Discussion
 Conflicts of interest
 References
 
The study population had attended the HSL between November 1999 and August 2003 for HAVS assessments as part of their health surveillance. All individuals attending the HSL HAVS referral centre undergo physical examination and medical interview by an experienced physician using a structured questionnaire. This questionnaire inquired about the frequency of blanching symptoms in the winter, and extent of blanching using the Griffin scoring system [9]. The volunteers in this study had individually consented to information from their assessments to be used for research purposes as part of a study approved by HSE's Ethics Committee. Arbitrarily, those consenting subjects who had vascular staging in their dominant hand were used for data analysis.

The frequency distribution of the number of blanching attacks per week in winter was investigated and the median used as a cut-off for defining ‘occasional’ or frequent attacks. In addition, the previously suggested cut-off value of 3 was also applied [11].

Volunteers reporting vascular symptoms in their dominant hand were staged according to the SWS (Table 1) [5] using the two different cut-offs for frequent attacks and the two modified scales (Tables 2 and 3).


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  		Table 1. The SWS

 

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  		Table 2. Modified SWS used in Dti assessments

 

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  		Table 3. Modified SWS suggested by Lawson (HSE expert workshop October 2003 and [9])

 

   Results
Top
 Abstract
 Introduction
 Methods
 Results
Discussion
 Conflicts of interest
 References
 
Of the 365 individuals who agreed to participate in the study, 185 had vascular symptoms in the dominant hand. Twenty of these individuals could not recall either the number of blanching attacks they had in the winter or the distribution of blanching, and were excluded from the study. None of the volunteers who were included in the study were thought to have primary Raynaud's disease.

The frequency of blanching attacks in the cold during the winter ranged from 1 to 60 attacks/week with a median value of 7 and was used as an alternate means of defining the frequency of attacks as occasional (≤7 per week) or frequent (>7 per week).

When the original SWS (Table 1) and the modified scale used for the Dti assessment of coal miners (Table 2) were applied with a blanching frequency cut-off of 3 per week, it was found that 58 and 46% of individuals with a history of cold-induced whiteness could not be staged, respectively (Figure 1). When a cut-off of 7 attacks/week was used, the relative proportion of individuals classified as 2V increased and the percentage of individuals who could not be staged fell to 31 and 27%, respectively. In those individuals who could not be staged, the majority had frequent attacks affecting the distal and middle phalanges of the fingers, which are not included in the SWS or Dti scales. The most recent modified scale [11] includes an additional category of frequent attacks affecting the distal and middle phalanges (2Vl) and therefore when this was applied using a cut-off of 3 the proportion of individuals who could not be staged fell to 2% and the proportion of individuals staged as 2V increased to 62%. In this study, using a cut-off of 3 attacks of blanching per week to distinguish occasional from frequent attacks, 17% of individuals would be classified as 2Ve and 45% as 2Vl using this scale. Changing the cut-off to 7 blanching attacks/week changed the proportion of individuals falling into the 2Ve and 2Vl categories to 42 and 15%, respectively. The SWS assume that there is a general relationship between blanching score and frequency of attacks such that they increase together. However, although we found a statistically significant relationship between the two parameters (Figure 2), it can only be described as poor (correlation coefficient = 0.24; P = 0.001).


Figure 1
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  		Figure 1. Proportions of individuals in each staging category depending on scoring scale used SWS 3 and SWS 7 refer to the SWSs with cut-offs for frequency of attacks of 3 and 7, respectively. Dti3 and Dti7 refer to the modified SWS used in the Dti assessment of coal miners and L3 and L7 refer to the modified scale proposed by Lawson (HSE expert workshop October 2003 and [9]) with a cut-off of 3 and 7, respectively.

 

Figure 2
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  		Figure 2. Relationship between blanching score and number of attacks in winter.

 

   Discussion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
Conflicts of interest
 References
 
This study shows that application of the modified SWS as published in recent HSE guidance [11] significantly reduces the level of HAVS cases that are problematic to stage when strictly applying definitions within the original SWS. This is evident whether a definition of 3 or 7 blanching attacks/week is used to distinguish the terms occasional from frequent. In agreement with Palmer and Griffin [7], we have also found that the number of individuals who can be categorized according to the original SWS is dependent upon the cut-off used to define frequent blanching attacks. We also highlight that frequency and extent of blanching are not closely related.

Individuals with frequent blanching attacks affecting the distal and middle phalanges constituted the majority of those who could not be staged using strict application of the original Stockholm Workshop and modified Dti scales. The recent modified scale [11] splits the 2V category and allows those reporting frequent attacks affecting the distal and middle phalanges to fall mainly into the 2Vl category. This modification [11] has also suggested that 3 attacks/week be used as the cut-off for differentiating frequent and occasional blanching attacks. However, we have found that the proportions of cases falling within the two subdivisions of 2V is sensitive to the cut-off used. This potential for misclassification may be important with regard to fitness-to-work decisions.

Staging the vascular aspect of HAVS relies upon accurate self-reporting of the number of fingers and phalanges affected and the frequency of attacks. An unpublished HSL study investigating the repeatability of reported blanching frequency in winter and the blanching score over an average follow-up time of 0.7 years (range 0.1–1.8 years) showed that recall of these symptoms varied with 95% limits of agreement of –9 to +12 blanching attacks/week. For the blanching score, the 95% limits of agreement were also wide (–9.2 to 13.9). This potential lack of repeatability in recall of extent and frequency of blanching could mean that an individual's staging may change as a result of recall uncertainty rather than genuine change in severity.

The SWS assumes that there is a positive relationship between the frequency of attacks and extent of blanching. Our data question the validity of this assumption. Thus, it may be necessary to consider which of the two factors is more important and weighted more heavily when classifying individuals. Some research suggests it is the frequency of attacks that is more disabling than the extent of blanching [7,8].

In conclusion, a significant proportion of individuals are not classifiable by strict application of the original, vascular SWS. Modifications to the scales improve the proportion that can be classified, but subdivision within Stage 2V is susceptible to the cut-off used to define frequent attacks. This may have important employment consequences. Therefore, because of this and the lack of repeatability in reporting of vascular symptoms, the identification of a reliable objective test remains an important consideration.


   Conflicts of interest
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conflicts of interest
References
 
None declared.


   References
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conflicts of interest
 References
 

  1. Proud G et al. Cold provocation testing and hand-arm vibration syndrome—an audit of the results of the Department of Trade & Industry scheme for the evaluation of miners. Br J Hand Surg 2003;90:1076–1079.

  2. Mason H, Poole K, Saxton JM. A critique of a UK standardised test of finger rewarming after cold provocation in the diagnosis and staging of hand-arm vibration. Occup Med (Lond) 2003;53:325–330.

  3. Poole K, Elms J, Mason H. The diagnostic value of finger systolic blood pressure and cold provocation testing for the vascular component of hand-arm vibration syndrome in health surveillance. Occup Med (Lond) 2004;54:520–527.

  4. Health & Safety Executive. Hand-Arm Vibration, vol. 88. Sudbury, Suffolk: HSE Books, 2001.

  5. Health & Safety Executive. Hand-Arm Vibration, vol. 88. Sudbury, Suffolk: HSE Books, 1994; 1–64.

  6. Palmer K, Coggon D. Deficiencies of the Stockholm vascular grading scale for hand-arm vibration. Scand J Work Environ Health 1997;23:435–439.[ISI][Medline]

  7. Palmer K, Griffin M. The clinical grading of Raynaud's phenomenon and vibration-induced white finger: relationship between finger blanching and difficulties in using the upper limb. Int Arch Occup Environ Health 2002;75:29–36.[ISI][Medline]

  8. Mason H, Poole K, Elms J. Upper limb disability in HAVS cases-how does it relate to the neurosensory or vascular element of HAVS. Occup Med (Lond) 2005;55:389–392.

  9. Griffin M. Handbook of Human Vibration. London: Academic Press, 1990; 1–988.

  10. Lawson I, McGeoch K. A medical assessment process for a large volume of medico-legal compensation claims for hand-arm vibration. Occup Med (Lond) 2003;53:302–308.

  11. Health & Safety Executive. Guidance on Regulations: Hand-Arm Vibration. The Control of Vibration at Work Regulations L140. Sudbury, Suffolk: HSE Books, 2005; 1–144.


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This Article
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