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