The 'Just 9 Questions' to Accurately Measure SCS Efficacy: A Revolutionary Outcome Assessment Method Demonstrated by an International Multicenter Study

Measuring the therapeutic efficacy of chronic pain treatment is difficult.

Saying 'my pain went from 10 to 6' is not enough.
Has your sleep improved? Have you returned to work? Do you feel more at ease?

However, asking patients to answer 30 or 40 questions every time is not realistic.
Patients get tired.

That is where this study comes in.

Using data from the international multicenter REALITY study (53 centers, 509 patients),
we statistically derived a 'minimum question set with accuracy equivalent to the full-length questionnaire.'
The conclusion was surprisingly simple.

What did this study do?

For 509 patients who received SCS or DRG (dorsal root ganglion) stimulation therapy,
the following four types of standard questionnaires were administered:

| Questionnaire Name | Content | Number of Questions |

| PROMIS-29 | Pain, physical function, mental state | 29 questions |
| ODI | Oswestry Disability Index | 10 questions |
| PCS | Pain Catastrophizing Scale | 13 questions |
| NRS | Numerical Rating Scale for pain | 1 question |

By applying principal component analysis (PCA), Pearson correlation, and
confirmatory factor analysis (CFA) to this data, we identified
'questions that do not lose accuracy even when removed.'

Surprising result: Just 9 questions were enough

The 5 major clusters of chronic pain revealed by PCA analysis:

1. 感情的苦痛（破局化・無力感・反芻）
2. 身体機能と障害（日常活動・社会参加）
3. 精神的健康（不安・うつ・疲労）
4. 睡眠障害
5. 疼痛強度

The questions needed to cover these are only 9 questions from PROMIS-29.

The 9 questions of the PROMIS-29 short form:

1. Physical Function: 'Are you able to go shopping?'

2. Anxiety: 'Did you feel restless?'

3. Depression: 'Did you feel hopeless?'

4. Fatigue: 'On average, how tired were you?'

5. Sleep ①: 'My sleep was refreshing'

6. Sleep ②: 'I had a problem with my sleep'

7. Social Roles: 'Did you have any trouble doing the things you wanted to do with your friends?'

8. Pain Interference: 'How much did pain interfere with your work at home?'

9. Pain Intensity: 'How would you rate your pain?'

Furthermore, it was possible to shorten the PCS (Pain Catastrophizing Scale) to 6 questions.

Comparison of Classification Accuracy

Results of comparing AUC (accuracy index) in ROC analysis:

| Index | Full Version AUC | Shortened Version AUC |

| Pain Intensity (NRS) | 0.744 | 0.744 (perfect match) |
| Pain Interference | 0.753 | 0.728 |
| Pain Intensity (PROMIS) | 0.750 | 0.750 (perfect match) |
| PCS Total Score | 0.701 | 0.704 |

For almost all indices, the shortened version maintained classification accuracy equivalent to the full version.

Important Finding: ODI can be replaced by PROMIS

Another important finding of this study is that
most of the information from the ODI (Oswestry Disability Index) can be replaced by PROMIS-29
.

• PROMIS-29 Physical Function and ODI: R=-0.73

• PROMIS-29 Social Roles and ODI: R=-0.72

• PROMIS-29 Pain Interference and ODI: R=+0.78

With such a high correlation, there is little need to collect ODI separately.
You can reduce the number of questionnaires.

Why were 2 questions needed for 'Sleep'?

While many other domains could be represented by 1 question, only sleep was selected for 2 questions.

The reason is simple.

Because the correlation between the 4 sleep questions in PROMIS-29 was lower than in other domains.
In other words, sleep quality is multifaceted and cannot be captured by a single question.

This is a clinically important implication.
Chronic pain and sleep are intricately intertwined.
It means that sleep, at the very least, should be evaluated thoroughly.

Clinical Application

Ready to use today for measuring the efficacy of SCS therapy

The shortened PRO demonstrated by this study can be used in the following situations:

Confirming efficacy during regular follow-ups

• Completing a questionnaire of 30+ questions every time is a heavy burden on patients

• If equivalent information can be obtained with a 9-question short version, more frequent measurement becomes possible

• 'How has your sleep been since last time? What about social activities?'—this can now be tracked

Application to digital health

• Regular 9-question surveys via smartphone apps

• Combining with wearable device data for more objective efficacy determination

Standardization of Patient-Reported Outcomes

• Covers five dimensions, not just pain intensity (NRS)

• Allows for a multifaceted evaluation of the 'true effect' of treatment

The 5 Dimensions to Evaluate

For patients who have undergone SCS treatment,
we recommend regular evaluation of these five areas:

| Dimension | Why it is important |

| Pain Intensity | The most fundamental indicator |
| Physical Function | Returning to daily activities is the treatment goal |
| Mental Health | Chronic pain and depression are closely linked |
| Sleep | Pain and sleep influence each other bidirectionally |
| Social Role | The core of QOL improvement |

Don't Forget 'Catastrophizing'

Although the PCS (Pain Catastrophizing Scale) has also been shortened,
you should not stop the evaluation itself.

'This pain will never go away,' 'The worst-case scenario will happen'—
these thought patterns are closely related to the intensity and disability of chronic pain.

Confirming catastrophizing thoughts during pre-SCS implantation psychological evaluation,
and performing cognitive behavioral therapy in parallel if necessary, leads to long-term success.

Summary

The therapeutic efficacy of SCS cannot be measured by pain scores alone.

However, long questionnaires place a burden on patients.

This study demonstrated with international multicenter data that '9 questions can provide the information of 29 questions.'

The implications for clinical practice are clear.
Frequently monitor the five dimensions of pain intensity, physical function, mental health, sleep, and social roles with fewer questions.

This is the best way to grasp the true efficacy of SCS therapy
and respond early.

As integration with digital health progresses,
this shortened PRO has the potential to become the standard
for next-generation chronic pain management.

Thank you for reading this far.

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Reference

Huygen F, Hagedorn JM, Falowski S, et al. Core patient-reported outcome measures for chronic pain patients treated with spinal cord stimulation or dorsal root ganglia stimulation. Health and Quality of Life Outcomes 2023;21:77. DOI: 10.1186/s12955-023-02158-2

Key References:

• Martinez-Calderon J, et al. Pain catastrophizing and function in chronic musculoskeletal pain. Clin J Pain. 2019;35(3):279-93.

• Dworkin RH, et al. Core outcome measures for chronic pain clinical trials: IMMPACT recommendations. Pain. 2005;113(1-2):9-19.