Reliability of the Neck Disability Index and Japanese Orthopedic Association questionnaires in adult cervical radiculopathy and myelopathy patients when administered by telephone or via online format

Background: The internal validity of long-term studies is significantly affected by the high loss to follow-up in the spine surgery population (>20%). Phone and email-based administration of patient-reported outcomes instruments is a less cumbersome approach for increasing response rates and assessment frequency while potentially decreasing follow-up burden on patients and physicians. Purpose: This study sought to validate simultaneous administration of the Neck Disability Index (NDI) and Japanese Orthopedic Association (JOA) questionnaires in patients with either cervical myelopathy and/or radiculopathy. Study Design/Setting: This is a single-center, randomized crossover phone and email validation of legacy outcome measures for cervical myelopathy and/or radiculopathy patients. Patient Sample: The study included nonsurgical along with pre- and postsurgical cervical myelopathy and/or radiculopathy patients presenting to a tertiary spine care center. Outcome Measures: NDI and JOA. Methods: Two-hundred and six patients (mean age: 58.5 years) were randomized in a 1:4 ratio to either email completion of the NDI and JOA before or after in-office completion, or to phone completion before or after in-office completion. An interval of 1 to 4 weeks was established between the administration of questionnaires. The difference between written in-office and corresponding email and phone versions was assessed with a paired t test. Homogeneity was assessed using intraclass correlation coefficients. Test-retest reliabilities were independently examined for postoperative patients (n=145). Recall bias was assessed in postoperative patients by calculating intraclass correlation coefficients for those with days between assessments lesser than the mean and for those greater. Differences in response rates between phone and email versions were assessed with McNemar's and Cochran-Mantel-Haenszel tests. Results: There was no significant difference between email and in-office versions (n=85) of the NDI (p=.17, Mean Paired Difference=1.34) and JOA (p=.64, Mean Paired Difference=0.11). No significant difference was seen between phone followed by in-office administration (n=32) of the NDI (p=.88, Mean Paired Difference=0.22) and JOA (p=.38, Mean Paired Difference=-0.22), nor between in-office administration followed by phone (n=44) for the NDI (p=.10, Mean Paired Difference=2.79) and JOA (p=.37, Mean Paired Difference=0.27). Intraclass coefficients (ICCs) of the email versions of the NDI and JOA were 0.88 and 0.78, respectively; of the phone-before-office versions of the NDI and JOA were 0.91 and 0.82; of the office-before-phone versions were 0.86 and 0.78. Similarly, strong intraclass correlation coefficients indicative of a lack of recall bias were found for “In-Office” and external assessments completed by postsurgical patients with days between assessments lesser and greater than the mean (ICC range 0.63–0.92). No significant difference was seen in completion rates between email and in-office questionnaire completion (p=.13) and phone-before-office and in-office questionnaire completion (p=.31). However, a significant difference was found in completion rates for phone-after-office questionnaires (p<.001). Conclusions: Administration of the NDI and JOA over phone and email in patients with cervical myelopathy or radiculopathy is valid with strong test-retest reliability and internal consistency. Phone and email administration of the NDI and JOA can reduce nonresponse rates and decrease the burden of follow-up and data acquisition. Follow-up phone reminders increase the response rate for administration of these patient-reported outcomes (PROs) via email.