Every week, I have to fill out two forms for my doctor. The first one is a line across the page. I make a mark to show how much back pain I'm having this week. The second is just a list of words from no pain to very severe pain. There's about five choices and I have to pick the one that best matches how I'm feeling. What's the point of using both of these tests? They look pretty much the same to me.
There are many different ways to measure pain. The simplest is asking a scale from zero (no pain) to 10 (worst pain) and ask the patient to give an objective (measurable) number to their subjective pain. This type of scale is called a numerical rating scale (NRS) or verbal rating scale (VRS). Another example of a verbal rating scale is the Likert-type scale. This is one of the scales your physician is using. You pinpoint the pain intensity or severity using word descriptors such as no pain, mild pain, moderate pain, severe pain, or very severe pain. Each of these pain categories is divided into five separate levels of pain with equal distance between each pain item on the scale. Another type of pain rating scale is the Visual Analog Scale (VAS). The VAS is made up of a straight line drawn on paper. The line can be drawn up and down (vertical) for patients who can't sit up or straight across (horizontal) for those who can be seated. In either case, the line is always 100 mm long (about four inches). For a horizontal line (straight across), the left end represents "no pain" and the right end represents "pain as bad as it could possibly be" or "worst possible pain." When the line is presented in a vertical orientation (up and down) for the client who is lying in bed and cannot sit up for the assessment, "no pain" is placed at the bottom and "worst pain" is put at the top. Any of these rating scales can be used to assess current pain, worst pain in the preceding 24 hours, least pain in the past 24 hours, or any combination the clinician finds useful. Both the Visual Analog Scale (VAS) and the Five-Item Verbal Rating Scale (VRS) have been tested and shown to be reliable and valid. In other words, each time the VAS or the VRS scale is used by itself, it really does measure pain in the same way from patient to patient and from one time period to another for each individual patient. Many health care professionals use these two tests interchangeably as if they measure exactly the same thing. We know from other studies that the two tests are highly correlated. That means if someone has a high (or low) pain score on one test, they will also have a high (or low) score when given the other test. But a recent study showed that the data collected from one test really isn't the same as the other. Basically, what this means is that using five-items on the Verbal Rating Scale (none to very severe) isn't the same as marking the 100 mm Visual Analog Scale (VAS) into five equidistant values. A VAS between zero and three doesn't really mean the patient's pain level is "mild" as measured by the same distance on the Verbal Rating Scale. A VAS between three and six doesn't correlate to "moderate pain" on the VRS. And more than seven (severe pain) on the VAS doesn't match up with the higher categories of the VRS. There is too much overlap of scores from one tool to the other to use them interchangeably as if they are measuring exactly the same pain levels. That could be why your physician is having you complete both forms -- to give as much useful information each week that can be compared from week to week.