Patient-reported allergies predict postoperative outcomes and psychosomatic markers after spine surgery.

Background Context: Prior studies have shown that patient-reported allergies can be prognostic of poorer postoperative outcomes.

Purpose: The objective of this study was to investigate the correlation between self-reported allergies and outcomes after cervical or lumbar spine surgery.

Study Design/setting: This is a retrospective cohort study at a single tertiary care institution.

Patient Sample: The patient sample included all patients undergoing cervical or lumbar spine surgery from 2009 to 2014.

Outcome Measures: The primary outcome measure was change in the EuroQol-5 Dimensions (EQ-5D) after surgery. Secondary outcomes included changes in the Pain Disability Questionnaire (PDQ) and in the Patient Health Questionnaire-9 (PHQ-9), achievement of the minimal clinically important difference (MCID) in these measures, and cost of admission.

Methods: Before and after surgery, EQ-5D, PDQ, and PHQ-9 were recorded for patients with available data. Paired Student t tests were used to compare changes in these measures after surgery. Multivariable linear and logistic regressions were used to assess the relationship between the log transformation of the total number of allergies and outcomes.

Results: A total of 592 cervical patients and 4,465 lumbar patients were included. The median number of reported allergies was two. The EQ-5D index increased from 0.539 to 0.703 for cervical patients and from 0.530 to 0.676 for lumbar patients (p<.01 for both). Patients experienced significant pain improvement by the PDQ (80.1-58.2 for cervical patients and 79.4-58.1 for lumbar patients, p<.01). Using multivariable logistic regression, the log transformation of the number of allergies predicted significantly higher odds of achieving the PDQ MCID (odds ratio [OR]=2.09, 95% confidence interval [CI] 1.05-4.15, p=.02, for cervical patients; OR=1.30, 95% CI 1.03-1.68, p=.03, for lumbar patients). However, this relationship was not durable for patients with follow-up exceeding 1 year. The log transformation of the number of allergies for lumbar patients predicted a significantly increased cost of admission (β=$3,597, p<.01) and trended toward significance among cervical patients (β=$1,842, p=.10).

Conclusions: Patient-reported allergies correlate with subjective improvement in pain and disability after spine surgery and may serve as a marker of postoperative outcomes. The relationship between allergies and PDQ improvement may be secondary to the short-term expectation-actuality discrepancy, as this relationship was not durable beyond 1 year.