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.