29 Aug Reading skin thickness using two-hands

The current OV instructions for measurement of skin thickness on day one of the TB test describe in great detail how the skin thickness must be measured. Currently the instructions state: “Raise a fold of skin between a finger and thumb, using one hand, at each clipped test site, measure the thickness of the fold with the callipers using your other hand, and record the measurements in millimetres in the testing record.”
This technique is closely scrutinised at audit and the technique has been widely and loudly criticised by some vets. The APHA have recently indicated that there is a willingness to review the existing wording in the OV instructions and to then see if the senior policy makers might be prepared to accept some adjustments in wording. The APHA were keen to base their discussions on some solid information alongside the anecdotal reports of dissatisfaction and concern that has been fed back to the Authority by the Veterinary Delivery Partners (VDP) in both England and Wales. In order to help get some objective reports and to measure how much of an issue this subject really is, XL Farmcare prepared a brief online survey on the topic. 411 OVs responded to the survey, representing around 30% of all OVs currently holding the OCQ(V)TT.
Many thanks to all those of you who kindly took the time and trouble to respond. How much of an issue is this topic? While the response rate to the survey was very good, which might indicate a high interest in the topic, one of the questions asked respondents how much the issues surrounding twohanded measurement troubled the respondents on a scale of one to ten (ten being: “it troubles me a lot” and zero being: “I’m perfectly content with the whole matter as it stands”). On average this issue scored just over six in this scale. How commonly is the two-handed technique used? We encouraged participants to be honest and to ‘tell us how it is’. However, we recognise that XL Farmcare is involved in audit of OV technique and
7XL Farmcare Newsletter Summer 2018
there were probably some cautious responses made. The survey asked respondents two questions regarding their existing technique for skin measurement on day one of the test. Six out of ten OVs use ball-ended callipers for measurement while the majority of the remainder use the Vernier style callipers to measure the skin. In terms of use of the two-handed technique, one third of all OVs say that they already use the two-handed technique either all the time or in all but very exceptional circumstances. A further third of OVs almost never use the two-handed technique or only occasionally do so on day one of the skin test. Almost half of the remaining OVs use the two-handed technique on more than three out of four occasions. So why is the obligation to use the two-handed technique an issue? Only one in ten respondents stated that they had no concerns regarding this technique. For the majority of the remainder, health and safety featured as their principal concern. A quarter said that they considered the technique to be impractical in certain cattle handling situations and a further quarter felt that measurement of skin thickness could be accurate and consistent without use of the two-handed technique. Should the testing instructions be improved? Only one in twenty respondents felt that the instructions were fine as they are. A third of the remainder felt
that references to the two-handed technique should be completely removed while the remaining two thirds selected an option stating that while the two-handed technique may be preferred, allowances should be made for circumstances when it cannot be applied. When asked why the instructions should be modified, health and safety was, once again, the dominant message. Several OVs suggested that the decision regarding the most appropriate technique for the circumstances should be left to the attending OV. Several others questioned the evidence for whether the two-handed technique yielded an improvement in the overall test sensitivity and specificity over and above allowing the attending OV to determine the most appropriate technique for the circumstances. This information, along with the results of a small pilot study where the use of differing techniques was compared at an XL Farmcare audit event, have now been shared with the decision makers within the APHA. It will be interesting to see whether any changes will come about but at least the survey results will allow some more objective reasoning.