Making the subjective objective: Are all types of pain equal?

My undergraduate research dealt with two types of pain constructs: chest pain related to cardiac disease and venipuncture pain (pain from an injection). During the analysis I even used ratings of venipuncture pain as a control variable for chest pain. However, I wonder if these two types of pain are really equal?

Venipuncture pain was rated with a visual analog scale in which patients mark on a line how much pain they experienced. Their line is then measured in centimetres to indicate how painful they found the stimulus on the 10 centimetre scale. This can be better than asking someone to rate their pain on a scale from 1 to 10, as subjects can remember what they previously answered. This pain measurement was then used to control for cardiac related pain as determined by scales like a modified version of the McGill Pain Questionnaire.

Intuitively, venipuncture pain & chest pain would be a little different. Venipuncture is probably related to a more pricking kind of pain that is very acute in nature, whereas chest pain, for a cardiac patient, may be something that occurs more chronically, is more of a tightness related pain, and may be more anxiety provoking (am I going to faint versus am I having a life threatening heart attack). Unfortunately, I was unable to find a definitive answer to whether venipuncture pain and chest pain are quantitatively the same.

Perhaps this is not the right question to be asking. Perhaps it doesn’t matter whether the pain is quantitatively the same or different by some “objective” measure (say an fMRI). Maybe what really matters is the person’s subjective, qualitative, interpretations of the pain. How much does the pain cause the specific person distress? This may be a more important predictor of other variables like health seeking behaviours. Maybe it’s the personal attributions and general pain sensitivity that make different types of pain more or less salient.

So maybe venipuncture pain was a good control for chest pain after all. Maybe technology will become more precise so we can measure acute differences in different types of pain. For now, subjective self-report measures of a painful experience more than suffice, and may even be better than future objective methods.

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