Preoperative Disability Influences Effectiveness of MCID and PASS in Predicting Patient Improvement Following Cervical Spine Surgery

Thursday, June 1, 2023

8:30 AM – 6:15 PM

Location: Salons 7-8

Co-Author(s)

PS

Pratyush Shahi, MBBS

Hospital for Special Surgery
New York, New York, United States

Co-Author(s)

OM

Omri Maayan, BS

Hospital for Special Surgery, United States

Presenting Author (Person doing the Podium Present(s)

TS

Tejas Subramanian, BS

Hospital for Special Surgery, United States

View E-Poster

Co-Author(s)

NS

Nishtha Singh, MBBS

hospital for special surgery, United States
SS

Sumedha Singh, MD, MBBS

Hospital for Special Surgery, United States
KA

Kasra Araghi, BS

Research Fellow
Hospital for Special Surgery
Scottsdale, Arizona, United States
OT

Olivia Tuma, BS

Hospital for Special Surgery
New York, New York, United States
MK

Maximillian Korsun, BS

Hospital for Special Surgery, United States
TA

Tomoyuki Asada, MD

Hospital for Special Surgery, United States
ES

Evan Sheha, MD

Hospital for Special Surgery, United States
JD

James E. Dowdell, MD

Spine Fellow
Hospital for Special Surgery
New York, New York, United States
SQ

Sheeraz A. Qureshi, MD, MBA

Attending Surgeon
Hospital for Special Surgery
York, New York, United States
SI

Sravisht Iyer, MD

Assistant Attending, Spine Surgery
Hospital for Special Surgery
New York, New York, United States

Submitter(s)

ES

Evan Sheha, MD

Hospital for Special Surgery, United States

Disclosure(s):

Omri Maayan, BS: No financial relationships to disclose

Tejas Subramanian, BS: No financial relationships to disclose

Nishtha Singh, MBBS: No financial relationships to disclose

Tomoyuki Asada, MD: No financial relationships to disclose

Sravisht Iyer, MD: No financial relationships to disclose

Introduction
There are two metrics for the interpretation of Neck Disability Index (NDI) - minimal clinically important difference(MCID) and patient acceptable symptom state(PASS). MCID is defined as the smallest change in NDI following surgery that would be clinically significant for the patient. PASS is an absolute postoperative NDI score, unlike MCID which is a change score, below which patients are expected to achieve an acceptable symptom state. It is unclear if there is a clear better metric between the two or which metric should be utilized when. Answering these questions can help substantiate our understanding regarding the clinical interpretation of NDI as an outcome measure.

Aims/Objectives
To compare the characteristics and predictive power of MCID and PASS when interpreting NDI following cervical spine surgery.

Methods
This retrospective cohort study included patients who underwent primary anterior cervical discectomy and fusion(ACDF), cervical disc replacement(CDR), or laminectomy and had >6 months of follow-up data. The global rating change(GRC) and NDI data at 6 months/1 year/2 years were analyzed. The response on GRC was used as the anchor to assess the improvement status - “Compared to preoperative, you feel 1) much better, 2) slightly better, 3) same, 4) slightly worse, or 5) much worse.” It was collapsed to a dichotomous outcome variable – a) improved (response of 1 or 2), b) not improved (response of 3,4, or 5). MCID was said to be achieved if the difference between preoperative and 1-year NDI was >10.5. PASS was said to be achieved if the 1-year NDI was < 21. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of MCID and PASS in terms of predicting improvement on GRC were calculated for the overall cohort and separately for patients with minimal (NDI < 30), moderate (NDI 30 – 49), and severe (NDI >50) preoperative disability. Two groups with patients who achieved PASS but not MCID and patients who achieved MCID but not PASS were also analyzed.

Results
141 patients (206 data points) were included. PASS had significantly greater sensitivity for the overall cohort (85% vs. 73% with MCID, p=0.02) (Table 1) and patients with minimal disability (96% vs. 53% with MCID, p< 0.001). Contrastingly, MCID had greater sensitivity for patients with severe disability (78% vs. 57% with PASS, p=0.05). Sensitivity was not significantly different for PASS and MCID in patients with moderate preoperative disability (83% vs. 92%, p=0.1). 17% of patients achieved PASS but not MCID and 9% of patients achieved MCID but not PASS, with the preoperative NDI being significantly greater in the latter. Most of these patients still reported improvement with no significant difference between the two groups (89% vs. 72%, p=0.13).

Conclusions
PASS is a better metric for patients with minimal preoperative disability and MCID is a better metric for patients with severe preoperative disability. Both metrics are equally effective for patients with moderate preoperative disability. Adequate interpretation of NDI using the PASS and MCID metrics warrants individualized application as their utility is highly dependent on the degree of preoperative disability.