Objective Markers to Evaluate Pain in Sickle Cell Disease

Background: Sickle cell disease is a genetic disorder resulting in rigidity of red blood cells during times of stress. This causes occlusion of blood flow through the vasculature, resulting in ischemic type pain and subsequent organ damage, ultimately leading to a significantly decreased life expectancy in these patients. The hallmark of sickle cell disease is episodic pain episodes that often need acute management in the emergency room. This pain is difficult to assess as there are no known objective pain markers. Currently, the assessment relies solely on the subjective statement by the patient. Unfortunately, in this population of chronic pain medication users, the subjective statement of having pain is often underestimated and patients suffer unnecessarily. It is the hypothesis of this study, that there are objective assessment and laboratory parameters that correlate with the subjective statement of pain.

Methods: This study was initiated as part of the 2008 Minority Medical Student Award Program. IRB approval was obtained through the Tulane University IRB. Adult sickle cell patients were recruited through the Sickle Cell Day Hospital (SCDH) at Tulane University. Upon entering the SCDH they were educated about the study, offered participation and consented as appropriate. Patients were assessed upon admission to the Sickle Cell Day Hospital during acute pain crises. Patients then returned for a follow up appointment when they were pain-free, 10–30 days after their pain crises. The assessment includes the Care Provider Pain Assessment (CaPPA – an observational tool to capture the care providers assessment of the patient’s behavior) questionnaire, routine lab work, vital sign measurement, and ESAS Score (a subjective symptom assessment scome) evaluation. The CaPPA captures an assessment of the patient’s facial expression, eye contact, verbalization of pain, body movements, interpersonal interactions, changes in activity patterns and changes in mental status. The lab assessments include the following parameters: WBC count, platelet count, reticulocyte count, levels of ferritin, LDH, bilirubin, hemoglobin, hematocrit, d-dimer, erythrocyte sedimentation rate, C-reactive protein and hemoglobin electrophoresis assessing the relative levels of Hemoglobin A1, F, S, and A2. The vital signs including blood pressure, pulse, temperature, O2 saturation, and respiration rate were measured.

Results: Thus far, there are 18 patients enrolled and 11 have completed the study. Data was retrieved from the initial visit during pain crises and follow-up visit when the patient was pain-free and was analyzed to note any increases or decreases in the values. The target enrollment for this study is 50 patients. Preliminary results are not sufficient to draw conclusions from the laboratory evaluations in this study. However, vital sign measurements show a consistent elevation in systolic blood pressure of 10 to 20 mmHg during pain from pain-free states. Scoring of pain, fatigue, anxiety and depression were also higher during pain than at follow-up. Patients were found to have a tendency to frown, have wrinkled foreheads and appear distressed when compared to non-pain states. Their body posture was more tense and rigid with overall restricted movement and gait changes, while in pain.

Conclusion: In conclusion, this study has started to identify some objective measures to support the subjective assessment of pain. This was a summer project initiated by a medical student as part of the 2008 Minority Medical Student Award Program. In addition to providing paramount exposure to clinical research, this was a tremendous learning experience. The study is ongoing and will continue to assess various parameters for their value in the objective evaluation of pain. We are planning full analysis after our target accrual of 50 patients has been met.