These authors reviewed consecutive patients undergoing primary RTSA between 2018 and 2019 who received preoperative baseline and follow-up PROMIS UE assessments at 12 months after surgery.
Domain-specific anchor questions pertaining to pain and function assessed at 12 months after surgery were used to determine minimal clinically important difference (MCID), substantial clinical benefit (SCB), and patient acceptable symptomatic state (PASS) values for the PROMIS UE.
Notably, all patients were distributed PROMIS UE assessments by trained research personnel at baseline before surgery. At 1 year after surgery, patients were contacted by e-mail every 5 days to complete follow-up assessments. At the end of the 1-month period, those who did not respond were recorded as lost to follow-up and excluded from this investigation.
They identified a total of 141 patients undergoing primary RTSA with completed preoperative PROMIS UE assessments in the study period, of whom only 95 (67.3%) completed 12-month assessments. There was a significantly greater proportion of male patients in the included cohort when compared with those lost to follow-up.
Among patients who completed both assessments, the average PROMIS UE score improved from 28.6 at baseline to 40.78 at 12 months. The visual analog scale score and American Shoulder and Elbow Surgeons (ASES) shoulder score also improved from 6.56 to 2.99 and from 38.58 to 77.89, respectively.
By use of an anchor-based method, the PASS value was 36.68 and the SCB value was 11.62. By use of a distribution-based method, the MCID value was calculated to be 4.27.
Higher preoperative PROMIS UE scores were a positive predictor in achievement of the PASS. This is an intuitive result - higher scores before surgery are likely to correlate with higher scores after surgery. 69.5% of the responding patients achieved the PASS.
Lower preoperative PROMIS UE scores were associated with obtaining SCB. This is an intuitive result - higher scores before surgery are likely to correlate with less improvement (benefit). 47.4% of the responding patients achieved the SCB.
Greater baseline forward flexion was negatively associated with achievement of the PASS and MCID. This result is not explained.
Comment: As noted above, all patients were distributed PROMIS UE assessments by trained research personnel at baseline before surgery. At 1 year after surgery, patients were contacted by e-mail every 5 days to complete follow-up assessments. Thus the methods for data collection after surgery (email) were not the same as the staff intensive data collection before surgery. At the end of the 1-month period, those who did not respond (one out of three) were recorded as lost to follow-up and excluded from the investigation.
This study demonstrates that non-response bias (see this link) may be associated with the use of the PROMIS: one third of the eligible patients did not provide a 12-month response. Even though the preoperative characteristics of the responders and non-responders were similar, there is no way to know if the outcomes of the missing 1/3 were similar to those of the responders. It appears that the characteristics of the PROMIS system has the potential for excluding a substantial number of them - possibly those with inferior results or those from less advantaged socio-economic situations (see this link).
For contrast compare the response rate from the above study with that in What is a Successful Outcome Following Reverse Total Shoulder Arthroplasty?, a study in which the more easily accessible Simple Shoulder Test enabled 87% of the patients in the original sample to provide two year followup.
While there have been many studies evaluating the characteristics of different outcome measures (see this link), there clearly needs to be further study of the response rates and the risk of non-response bias for each metric.
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