Do Patients Accurately Recall Pain Levels Following Sacroiliac Joint Steroid Injection? A Cohort Study of Recall Bias in Patient-reported Outcomes.

BACKGROUND: Sacroiliac joint (SIJ) injections are crucial in the diagnostic toolkit for evaluating SIJ pathology. Recall bias is an important component in patient-reported outcomes that has not been well studied in SIJ injection.

OBJECTIVE: The purpose of this study was to characterize the accuracy, direction, and magnitude of pain level recall bias following SIJ steroid injection and study the factors that affect patient recollection.

STUDY DESIGN: Prospective cohort study.

SETTING: Level 1 academic medical center.

METHODS: Using standardized questionnaires, baseline Numeric Rating Scale (NRS-11) scores were recorded for patients undergoing SIJ steroid injections at preinjection, at 4 hours postinjection, and at 24 hours postinjection. At a minimum of 2 weeks postinjection, patients were asked to recall their preinjection, 4-hour, and 24-hour postinjection NRS-11 scores. Actual and recalled NRS-11 scores were compared using paired t tests for each time interval. Multivariable linear regression was used to identify factors that correlated with consistent recall.

RESULTS: Sixty patients with a mean age of 66 years (65% women) were included. Compared to their preinjection pain score, patients showed considerable improvement at both 4 hours (mean difference [MD] = 3.28; 95% CI, 2.68 - 3.89), and 24 hours (MD = 3.23; 95% CI, 2.44 - 4.03) postinjection. Patient recollection of preinjection symptoms was more severe than actual (MD = 0.65; 95% CI, 0.31 - 0.99). Patient recollection of symptoms was also more severe than actual at 4 hours (MD = 0.50; 95% CI .04 - 1.04) as well as at 24 hours postinjection (MD = 0.80; 95% CI, 0.16 - 1.44). The magnitude of recall bias was mild and did not exceed the minimal clinically important difference. There was a moderate correlation between actual and recalled pain levels when comparing preinjection with the 4-hour postinjection NRS-11 score (correlation coefficient [r] =0.64; P < 0.001) and moderate correlation when comparing preinjection with the 24-hour postinjection NRS-11 score (r = 0.62; P < 0.001). Linear regression models showed that at preinjection, patients with a lower body mass index and the presence of coexisting psychiatric diagnoses were better at recalling their pain (P < 0.05). Patients with a higher body mass index also experienced less pain relief when comparing preinjection with the 4-hour postinjection NRS-11 score (P < 0.05).

LIMITATIONS: Recall pain scores were obtained via telephone surveys, which can lead to interview bias. One patient died, and 3 were lost to follow-up. We did not control for patient use of adjunctive pain relief modalities, which may modulate the overall response to injection. SIJ injections can also be diagnostic, so some patients may not have shared the same indication for injection or pain-generating diagnosis.

CONCLUSIONS: Patients had favorable pain level responses to their SIJ steroid injection for both actual and recall surveys. Although patients demonstrated poor recall of absolute pain scores at preinjection, 4-hour postinjection, and 24-hour postinjection, they demonstrated robust recall of their net pain score improvement at both 4- and 24-hours postinjection. These findings suggest that there is utility in using patient recollection to describe the magnitude of pain relief following treatment for sacroiliac joint dysfunction.