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Comment on StEP
Posted by Hans_Timmerman on 18 May 2009 at 08:43 GMT
Comment on: A novel tool for the assessment of pain: Validation in low back pain
(Scholz et al. 2009)
With interest we read the article about the validation for the distinction between patients with radicular and axial low back pain (LBP) of the standardized evaluation of pain (StEP) by Scholz et al . The high sensitivity and specificity and relative easy use makes this instrument a promising one. However, we have some major concerns about this novel assessment tool.
(1) StEP is constructed as a tool that differentiates in different pain phenotypes independent of etiology, e.g. construe a relation between (sub-)patterns en biological mechanisms. Neuropathic pain is considered, especially in a mechanism based classification, to be present only when there are definite signs of a nervous lesion [2,3]. What about nociceptive nerve pain as a biological mechanism in patients with diabetic neuropathy?
(2) Is the validation of this instrument performed for the diagnosis of neuropathy or for the diagnosis of radiculopathy in patients with LBP? Is the distinction between radicular and axial low back pain (LBP) the same as the ability to distinguish between neuropathic pain and non-neuropathic pain? Or is chronic radicular low back pain with radiculopathy a pain syndrome in which both types of pain are present? According to a substantial number of studies the latter seems to be so [4-7].
(3) In recent years an effort is made to move towards a rational and symptom-based treatment for the improvement of LBP therapy: Physicians should distinguish the nociceptive and neuropathic pain components in their patients and realize there are co-morbid conditions [5,8]. Treede et al defined neuropathic pain as ‘pain arising as a direct consequence of a lesion or disease affecting the somatosensory system’ . Following this grading system and according to Bennett , a combination of neuropathic and non-neuropathic pain is possible and pain itself can be more or less neuropathic of origin. It is the greatest challenge to diagnose the group of patients that doesn’t fit exactly in the radicular or axial group. In this study six patients (4%) are excluded after clinical classification of their pain but before statistical analysis. Inclusion of these six patients in the analysis should be considered because of ‘real-life clinical practice’.
(4) Finally, we have concerns about the use of spinal magnetic resonance imaging (MRI) in only 52% of the patients. As written in the article, the gold standard should be a conclusive clinical diagnosis which is based on several sources including additional investigations as MRI. In patients with axial LBP in 26 cases a spinal MRI is present. Of these, 5 patients are diagnosed after clinical diagnosis as radicular LBP. When no MRI is performed only 1 of 40 patients is re-diagnosed as radicular LBP. To our meaning, from every patient there should be a MRI to standardize the final diagnosis in studies validating assessment tools for the distinction between radicular en axial LBP.
Hans Timmerman 1
André P. Wolff 1
Eric C.A.M. van Rijswijk 2
Kris C.P. Vissers 1
1. Radboud University Nijmegen Medical Centre, Department of anesthesia, pain and palliative medicine, 6500 HB Nijmegen, The Netherlands
2. Radboud University Nijmegen Medical Centre, Department of general practice, 6500 HB Nijmegen, The Netherlands
1. Scholz J, Mannion RJ, Hord DE, Griffin RS, Rawal B, Zheng H, Scoffings D, Phillips A, Guo J, Laing RJ, Abdi S, Decosterd I, Woolf CJ (2009) A novel tool for the assessment of pain: validation in low back pain. PLoS Med;6:e1000047.
2. Woolf CJ, Bennett GJ, Doherty M, Dubner R, Kidd B, Koltzenburg M, Lipton R, Loeser JD, Payne R, Torebjork E (1998) Towards a mechanism-based classification of pain? Pain;77:227-229.
3. Woolf CJ, Max MB (2001) Mechanism-based pain diagnosis: issues for analgesic drug development. Anesthesiology;95:241-249.
4. Treede RD, Jensen TS, Campbell JN, Cruccu G, Dostrovsky JO, Griffin JW, Hansson P, Hughes R, Nurmikko T, Serra J (2008) Neuropathic pain: redefinition and a grading system for clinical and research purposes. Neurology;70:1630-1635.
5. Baron R, Tolle TR (2008) Assessment and diagnosis of neuropathic pain. Curr Opin Support Palliat Care;2:1-8.
6. Bennett MI, Smith BH, Torrance N, Lee AJ (2006) Can pain can be more or less neuropathic? Comparison of symptom assessment tools with ratings of certainty by clinicians. Pain;122:289-294.
7. Rasmussen PV, Sindrup SH, Jensen TS, Bach FW (2004) Symptoms and signs in patients with suspected neuropathic pain. Pain;110:461-469.
8. Freynhagen R, Baron R, Gockel U, Tolle TR (2006) painDETECT: a new screening questionnaire to identify neuropathic components in patients with back pain. Curr Med Res Opin;22:1911-1920.
We thank Hans Timmerman and colleagues for their comments on our article.
Ad (1). The term nociceptive pain is widely misused. Its meaning, first defined by Charles Sherrington, is restricted to pain elicited by a noxious stimulus acting on intact, high threshold nociceptors. Pain caused by diabetic neuropathy is a direct consequence of a disease affecting the somatosensory nervous system and, therefore, constitutes neuropathic pain1. We would consider a painful response in patients who suffer from neuropathic pain nociceptive only when it is a pain that reflects the presence of noxious stimulation. If the painful response is exaggerated, this would represent hyperalgesia and be a neuropathic sign, as would be a reduced pain threshold and the presence of spontaneous pain.
Ad (2). We validated StEP for the distinction between radicular and axial low back pain (LBP). Radicular LBP comprises pain arising from the compression and inflammation of a spinal nerve root as well as pain that is elicited by degenerative changes of the spine, which are the primary cause of axial LBP. StEP helps identify symptoms and signs that specifically indicate the neuropathic component of radicular LBP. We do not claim (and explicitly state so in the article) that those elements of StEP, which separate between radicular and axial LBP, would have the same discriminatory power in other conditions of neuropathic or non-neuropathic pain.
Ad (3). The gold standard that we applied as reference for the validation of StEP was concordant clinical diagnosis by an interdisciplinary team of at least two experienced physicians and a spinal physiotherapist. This criterion was not fulfilled in the six patients that we excluded from the analysis. In clinical practice, such ambiguity is a major challenge and we hope that StEP will help overcome this diagnostic problem. But for the purpose of this study it was essential to define an appropriate standard against which to compare the outcome of StEP. Inclusion of the patients would not have altered the results.
Ad (4). We only considered MRIs performed at the study center to evaluate sensitivity and specificity of that technique because we wanted to avoid inconsistencies in the technical conditions, under which imaging was carried out. This does not mean that the remainder of the patients was not examined by MRI, only that these MRIs were performed at a different center. Both external MRIs and MRIs carried out at the study center were taken into account for the clinical diagnosis of radicular versus axial LBP.
Joachim Scholz, MD
Clifford J. Woolf, MD, PhD
Massachusetts General Hospital, Department of Anesthesia and Critical Care, Neural Plasticity Research Group, Charlestown, MA 02129, USA
1. Treede RD, Jensen TS, Campbell JN, Cruccu G, Dostrovsky JO, et al. (2008) Neuropathic pain. Redefinition and a grading system for clinical and research purposes. Neurology 70: 1630–1635.