HSS Dysphagia and Dysphonia Inventory (HSS-DDI) Following Anterior Cervical Fusion: Patient-Derived, Validated, Condition-Specific Patient-Reported Outcome Measure Outperforms Existing Indices.

BACKGROUND: Dysphagia and dysphonia are common complications after anterior cervical spine surgery; however, reported prevalences vary greatly due to a lack of reliable clinical standards for measuring postoperative swallowing and speech dysfunction. The Hospital for Special Surgery Dysphagia and Dysphonia Inventory (HSS-DDI) was developed as a patient-derived, patient-reported instrument to measure dysphagia and dysphonia more accurately after anterior cervical spine surgery than existing indices.

METHODS: This multiphase survey-development study implemented a mixed-methods approach. Phase 1 involved qualitative assessment of postoperative patient-reported swallowing or speaking deficiencies to assemble a draft survey. Phase 2 established test-retest reliability and finalized the 31-item HSS-DDI. Phase 3 compared the HSS-DDI with the Swallowing-Quality of Life (SWAL-QOL) questionnaire and the M.D. Anderson Dysphagia Inventory (MDADI) for validity and responsiveness.

RESULTS: Phase 1, performed to formulate the draft survey, included 25 patients who were asked about speech and swallowing dysfunction after anterior cervical spine surgery involving at least 3 vertebral levels. Phase 2 included 49 patients who completed the draft survey twice. The mean scores (and standard deviation) for each administration of the HSS-DDI were 67 ± 24 and 75 ± 22, the Cronbach alpha coefficients were both 0.97, and the intraclass correlation coefficient was 0.80. The 31-item HSS-DDI was finalized with all but 2 items having weighted kappa values of ≥0.40. Phase 3 included 127 patients and established external validity, with most correlation coefficients between the HSS-DDI and the SWAL-QOL and MDADI ranging from 0.5 to 0.7. Internal validity was established by identifying worsening HSS-DDI scores with increases in the number of vertebral levels involved (p = 0.02) and in the Surgical Invasiveness Index (p = 0.006). HSS-DDI responsiveness ascertained by effect size (0.73) was better than that of the SWAL-QOL and MDADI. The average administration time for the HSS-DDI was 2 minutes and 25 seconds.

CONCLUSIONS: The HSS-DDI is efficient, valid, and more responsive to change after anterior cervical spine surgery than existing surveys.

CLINICAL RELEVANCE: The HSS-DDI fills a gap in postoperative assessment by providing a reliable, more clinically sensitive, patient and condition-specific evaluation of dysphagia and dysphonia prospectively and longitudinally.