[Classification of chronic pain. Quantification and grading with the Mainz Pain Staging System].

INTRODUCTION: Chronic pain is an individually variable experience, incorporating physical, psychological and social dimensions. Chronic pain occurs in a broad spectrum of severity; therefore, a grading procedure is of crucial importance in clinical research and in epidemiologic studies. The Mainz Pain Staging System is an interview-administered, multi-dimensional measure of chronic pain severity. The system suggests grading chronic pain in terms of 4 axes: time (persistence), spreading of pain site, medication use, and health care utilization. The whole scale consist of 10 items. The resulting score is used to classify the pain problem in three stages (I, II, III). Analysing the broader validity and parametric properties of the staging system is the purpose of the present study.
METHODS: The staging system and psychosocial data were administered to 542 consecutive patients of different diagnoses who attended one of six pain clinics in the year 1995/96. In a time period of 3 months since first contact, treatment procedures were registered. Three months after first contact patients rated the effectiveness of treatment concerning reduction of pain intensity.
RESULTS: According to the criteria of the staging system 25% of the sample belonged to each stage I and stage III, whereas 50% were classified to stage II. As a measure of validity, chronic pain status demonstrated significant correlation with psychological impairment, disability and time off work, whereas there was no correlation to pain intensity and persistence of pain. Surprisingly we found no difference in amount and quality of treatment between patients who were graded as severe pain patients (stage III) and the other stages. Furthermore, effectiveness of treatment also did not differ between the three stages. We made several proposals for optimizing the staging system.
CONCLUSION: Given the high prevalence of recurrent and chronic pain as well as the broadness of severity, an important issue on further research is identification of factors which influence the chronification process. For this purpose improved measures of graded classification of pain status are needed.