MONTREAL--A new instrument for measuring pain intensity--the visual analogue thermometer (VAT)--developed to overcome some of the disadvantages of the conventional visual analogue scale (VAS)--has proved "valid, accurate, and clinically useful" in two studies, say Manon Choinière, PhD, of the Burn Centre, Hotel-Dieu Hospital of Montreal and the University of Montreal, and Rhonda Amsel, MSc, of the Department of Psychology, McGill University.
MONTREAL--A new instrument for measuring pain intensity--the visualanalogue thermometer (VAT)--developed to overcome some of thedisadvantages of the conventional visual analogue scale (VAS)--hasproved "valid, accurate, and clinically useful" in twostudies, say Manon Choinière, PhD, of the Burn Centre,Hotel-Dieu Hospital of Montreal and the University of Montreal,and Rhonda Amsel, MSc, of the Department of Psychology, McGillUniversity.
With the VAS, patients must make a mark along a 10-cm line thathas "no pain" and "unbearable pain" as thetwo extremes. The scale is then scored by measuring the distancein millimeters from "no pain" to the patient's mark.
Dr. Choinière describes the potential disadvantages ofthis scale as follows: (1) It may be physically awkward to completefor burn patients who have difficulty holding a pen or for thosewith perceptual or motor problems; (2) it does not provide animmediate result since the line has to be measured; and (3) itmay be difficult for some patients to understand.
The VAT, an adaptation of the VAS, was developed at the Burn Centre,Hotel-Dieu Hospital of Montreal. It does not require any writingor use of the hands by the patient.
The VAT consists of a rigid white cardboard strip with a horizontalblack opening through which a red band can be moved from leftto right using a tab on the back of the device.
The left and right extremities of the opening are labeled "nopain" (or "aucune douleur") and "unbearablepain" ("dou-leur insupportable"). The patient istold that the device works like a thermometer except that it ismeasuring pain intensity in millimeters rather than body temperaturein degrees.
The patient or an assistant slowly moves the red band to a positionindicating the patient's pain intensity. "The more intensethe pain, the more the red band lengthens toward the limit ofunbearable," Dr. Choinière explains. This can thenbe read as a numerical value by using the 10-cm ruler printedon the reverse side of the device.
"The design of the VAT makes it suitable and effective forclinical use and as an outcome measure in clinical trials,"Dr. Choinière says.
The first of the two studies of the new device was carried outin a group of 65 chronic pain patients who rated their pain intensityusing the VAT, a standard VAS, and the McGill Pain Questionnaire,which consists of 20 categories of adjectives from which patientschoose those that best describe their pain.
In the second study, 243 healthy adult volunteers quantified theintensity of a set of descriptive pain terms with the VAT, a numericalscale (with pain rated 0 to 10), and a VAS.
There were no major differences in the relative sensitivity ofthe VAT, compared with the standard VAS, with both scales givingcomparable pain estimates, and there were no major problems insubjects' understanding or using either scale (J Pain SymptomManage 11:299-311, 1996).
A substantial number of study participants (37%) said they preferredthe VAT, while 26% favored the standard VAS, and 37% had no preference.
Although the VAT measures only the intensity component of thepain experience, Dr. Choinière points out that it couldeasily be adapted for measuring others aspects of pain, such aspatient's mood and pain relief, by simply adding a slider to changethe anchor words at either end of the scale.