Properties of the SLANSS tool for assessment and prognosis in whiplash

Ashley Smith PT, PhD(c), FCAMPT

Dave Walton PT, PhD, FCAMPT

Michele Sterling PT, PhD

Outline

Introduction – why the SLANSS?

Hypotheses

Concurrent validity

Predictive validity

Methods

Results

Conclusions/Recommendations

Introduction

S-LANSS

Self-report version of the Leeds Assessment of Neuropathic Signs and Symptoms

7-item paper-and-pencil form

Intended to capture signs and symptoms of “neuropathic” pain

For screening: each item weighted, score ≥ 12 best indicator of Pain of Predominantly Neuropathic Origin (POPNO)

Screening Properties

Validated (construct, convergent, internal consistency) against expert opinion with no ‘Gold Standard’ available

Unaided: 74% Sensitivity; 76% Specificity Bennett, 2005

Validated in single body regions of pain

Bouhassira, 2011

Fails to identify 25% of pain with clinical Dx

Not suitable for assessment of Rx effects Bouhassira, 2011

Use in MSK research

‘None of the descriptors was pathognomonic or even specific for neuropathic pain’ Bennett, 2005

Sterling & Pedler, 2008: 85 people with acute whiplash (<4 weeks) (54 females, age 36.27 12.69 years)

34% scored S-LANSS ≥ 12; with corresponding

Higher pain/disability, cold hyperalgesia, cervical mechanical hyperalgesia, and less elbow extension with the BPPT

Pressure pain thresholds (PPTs) at distant sites and psychological distress (GHQ-28) were not different between the groups

Unknown clinimetric properties

Do ‘neuropathic signs & symptoms’ constitute one broad domain, or is there more than one factor in the scale?

How is the scale (or sub-scales if present) related to other clinical indicators, such as pain threshold or disability?

Can the scale, or its subscales, be used to predict short-term outcome after acute whiplash?

Objectives

1. To explore the factor structure of the SLANSS in a sample of people with whiplash-associated disorder (WAD)

2. To evaluate the usefulness of the scale, or sub-scales, in predicting current or future WAD-related pain and disability

EFA Sample (WAD)

N = 203 Mean (range)

Sex (% female) 67%

Age (y) 38.4 (19-70)

Duration (days) 358.3 (0-6330)

NPRS (0-10) 4.7 (0-10)

NDI (/100)* 35.3 (0-80)

Cx PPT (kPa) 225.4 (5.0-1163.2)

Tib Ant PPT (kPa) 416.4 (71.7-1209.3)

NPRS = Numeric Pain Rating Scale, NDI = Neck Disability Index, Cx PPT = pressure pain threshold at the cervical spine, TA PPT = pressure pain threshold at the belly of the tibialis anterior.*: n = 135 subjects for NDI only

Factor structure of S-LANSS

3-factor solution optimal, explaining 62.2% of variance in score

Factor 1: Superficial symptoms (32.4%)Q2 (skin colour change), Q3 (skin sensitive to touch), Q5 (skin hot)

Factor 2: Active tests (17.3%)Q6 (rub the painful area), Q7 (press on the painful area)

Factor 3: Deep symptoms (12.5%)Q1 (pins & needles), Q4 (sudden, bursting pain)

Concurrent validity

Based on EFA, hypotheses were:

1. Active tests would be most strongly associated with local (cervical) PPT

2. None of the factors would be associated with distal (Tib. Ant.) PPT

3. Factor 3 (deep symptoms) would be most strongly associated with NPRS

4. All 3 factors would be independently associated with NDI

Concurrent validity

Hypothesis 1: Of the 3 subscales, association between active tests and local PPT would be strongest

“Superficial symptoms” subscale was equally associated with local PPT

Partially supported

****

Concurrent validity

Hypothesis 2: None of the subscales would be associated with TA PPT

“Superficial symptoms” subscale showed a significant association with distal PPT

Partially supported

*

Concurrent validity

Hypothesis 3: Factor 3 (deep symptoms) would be most strongly associated with NPRS

While significant, “Deep symptoms” showed the weakest association with NPRS of the 3 subscales.

Not supported

Concurrent validity

Hypothesis 4: Each subscale would be independently associated with NDI

After stepwise multiple linear regression, all 3 subscales were retained, explaining 35.7% of the variance in NDI

Supported

Summary of concurrent validity

The S-LANSS appears to possess 3 important subscales: superficial symptoms, deep symptoms and active tests

The ‘superficial’ and ‘active’ subscales are significantly associated with local PPT

‘Superficial’ is also associated with distal PPT

All three are associated with NPRS

All three explain unique significant variance in NDI

Predictive validity (acute WAD)

Hypotheses:

1. Each of the 3 subscales would explain significant unique variance in follow-up NDI scores after controlling for age, sex and baseline pain intensity

2. Each of the 3 subscales would explain significant unique variance in follow-up PTSD scores, after controlling for age, sex and baseline pain intensity

Methods

Subjects with acute (<60 days) WAD were recruited

Data:

Demographics (age, sex)

NPRS, NDI

Local (C-spine) and Distal (Tib. Ant.) PPT

S-LANSS

3 months later NDI and PTSD data were collected

Sample

N = 118

Sex (% female) 70.3%

Mean (range)

Age (y) 37.8 (19-70)

Duration (days) 19.0 (0-52)

NPRS (0-10) 4.1 (0-10)

NDI (/100)* 30.3 (0-80)NPRS = Numeric Pain Rating Scale, NDI = Neck Disability Index.*: n = 72 subjects for NDI only

Results

Zero-order correlations, 3-month NDI as outcomeVariable R P

Age 0.14 0.14

NPRS 0.34 <0.01

Baseline NDI 0.79 <0.01

Cx PPT -0.28 <0.01

Tib Ant PPT -0.17 0.09

S-LANSS

Superficial symptoms 0.31 <0.01

Deep symptoms 0.28 <0.01

Active tests 0.27 <0.01

Sex Female (n=77) Male (n=31)

21.2 (18.3)15.9 (13.6)

0.15

Results

Zero-order correlations, 3-month PTSD as outcomeVariable R P

Age 0.02 0.88

NPRS 0.32 <0.01

Baseline NDI 0.65 <0.01

Cx PPT -0.39 <0.01

Tib Ant PPT -0.34 <0.01

S-LANSS

Superficial symptoms 0.35 <0.01

Deep symptoms 0.36 <0.01

Active tests 0.18 0.06

Sex Female (n=77) Male (n=31)

0.03 (1.02)-0.09 (0.90)

0.32

Results: Predictive Validity

Multiple linear regression

Age and sex entered first, followed by NPRS, Local and Distal PPT, and 3 S-LANSS subscales

NDI: 4 variables were retained in the model, explaining 24.2% of the variance in NDI

Baseline NPRS, Deep symptoms subscale, Age, Cervical PPT

PTSD: 3 variables were retained, explaining 25.9% of the variance in PTSD score

Cervical PPT, Deep symptoms subscale, Superficial symptoms subscale

Discriminatory Accuracy

Ability of S-LANSS total weighted score to discriminate between those ‘at risk’ of NDI >10/100 after 3 months from those not at risk.

AUC: 0.68

Best cut-score: score of 10 or higher:

Se: 0.52, Sp 0.76, +LR 2.14, -LR 2.60

AUC = 0.68

Discriminatory Accuracy

Subscales

Superficial symptoms: AUC = 0.60

Deep symptoms: AUC = 0.62

Active tests: AUC = 0.63

All of the scales (total and subscales) are more specific than they are sensitive

High risk of false negatives with low scores, but high scores are particularly problematic

Predictive validity: Summary

After controlling for baseline pain, sex and gender, the deep symptoms subscale contributes significant predictive power to the model for 3-month NDI and PTSD

The superficial symptoms subscale also uniquely predicts 3-month PTSD

None of the scales (total or subscales) are useful screening tools when used on their own