We demonstrate and evaluate a method for modeling acute pain resolution in individual patients over 6 days following an emergency department visit for an acutely painful condition. Five hundred and thirteen patients presenting with acutely painful conditions provided 11-point numerical ratings of pain intensity at discharge from an emergency department and daily thereafter for a total of 6 days. Latent growth curve modeling with a linear fit yielded measures of initial pain intensity (intercept) and rate of pain resolution (slope) for each individual patient. The linear fits provided good approximations of individual pain trajectories. The average patient had intercept of 6.57 with a slope of -.61. On Day 4, 54.6% of patients reported a pain level equal to or greater than 4. Classification of individual patients by slope revealed that 79% of the sample had the expected negative slope for acute pain resolution while 21% had flat or positive slopes, indicating lack of pain resolution or worsening of pain over time following discharge. The standard errors of measurement for the acute pain trajectories were markedly smaller than those for conventional pain ratings, indicating that the trajectory approach to pain measurement improves measurement precision.
Perspective: The acute pain trajectory provides more information than conventional pain measurement and increases measurement precision. It provides a means of determining the efficacy of acute pain management in the emergency department. The rate of pain resolution is a potentially valuable outcome measure for controlled clinical trials.
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