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Spine J. 2018 Jun;18(6):941-947. doi: 10.1016/j.spinee.2017.10.003. Epub 2017 Oct 12.

Clinical classification criteria for neurogenic claudication caused by lumbar spinal stenosis. The N-CLASS criteria.

Author information

1
Division of Rheumatology, University Hospitals of Geneva, 4 rue Gabrielle-Perret-Gentil, 1205, Geneva, Switzerland. Electronic address: stephane.genevay@hcuge.ch.
2
Division of Rheumatology, University Hospitals of Geneva, 4 rue Gabrielle-Perret-Gentil, 1205, Geneva, Switzerland; Quality of Care Division, University Hospitals of Geneva, Rue Gabrielle Perret-Gentil, 1205, Geneva, Switzerland.
3
Arthritis Research UK Primary Care Centre, Research Institute for Primary Care & Health Sciences, Keele University, Staffordshire, ST5 5BG, UK.
4
Unidad de la Espalda Kovacs Hospital Universitario HLA-Moncloa Avda de Valladolid 81, 28008, Madrid, Spain.
5
Department of Rheumatology, Henri-Mondor Hospital, 51 Ave du MI de Lattre de Tassigny, Créteil, France.
6
The Spine Center, New England Baptist Hospital, 125 Parter Hill, MA 02120, Boston, USA.
7
Physical Medicine and Rehabilitation, University hospital of Lausanne, Av Pierre-Decker 4, Switzerland.
8
Physical Medicine and Sport Traumatology Department, University and University Hospital of Liège, Av de l'hôpital, B35, 4000 Liège, Belgium.
9
Department of Orthopaedic Surgery, Massachusetts General Hospital, 55 Fruit St., Yawkey 3A, MA 02114, Boston, USA.
10
Orthopedic and Arthritis Center for Outcome Research, Brigham and Women's Hospital, 75 Francis Street, BTM 5016, MA 02115, Boston, USA.
11
Division of General Internal Medicine, Massachusetts General Hospital, 50 Stanifort Street, Room 966, MA 02114, Boston, USA.

Abstract

BACKGROUND CONTEXT:

Because imaging findings of lumbar spinal stenosis (LSS) may not be associated with symptoms, clinical classification criteria based on patient symptoms and physical examination findings are needed.

PURPOSE:

The objective of this study was to develop clinical classification criteria that identify patients with neurogenic claudication (NC) caused by LSS.

STUDY DESIGN:

This study is a two-stage process that includes Phase 1, the Delphi process, and Phase 2, the cross-sectional study.

PATIENT SAMPLE:

Outpatients were recruited from spine clinics in five countries.

OUTCOME MEASURE:

The outcome measure includes items from the patients' history and physical examination.

METHODS:

In Phase 1, a list of potential predictors of NC caused by LSS was based on the available literature and was evaluated through a Delphi process involving 17 spine specialists (surgeons and non-surgeons) from eight countries. In Phase 2, 19 different clinical spine specialists from five countries identified patients they classified as having (1) NC caused by LSS, (2) radicular pain caused by lumbar disc herniation (LDH), or (3) non-specific low back pain (NSLBP) with radiating leg pain. The patients completed survey items and the specialists documented the examination signs. Coefficients from general estimating equation models were used to select predictors, to generate a clinical classification score, and to obtain a receiver operating characteristic curve. Conduction of the Delphi process, data management, and statistical analysis were partially supported by an unrestricted grant of less than 15,000 US dollars from Merck Sharp & Dohme. No fees were allocated to participating spine specialists.

RESULTS:

Phase 1 generated a final list of 46 items related to LSS. In Phase 2, 209 patients with leg pain caused by LSS (n=63), LDH (n=89), or NSLBP (n=57) were included. Criteria that independently predicted NC (p<.05) were age over 60 years, positive 30-second extension test, negative straight leg test, pain in both legs, leg pain relieved by sitting, and leg pain decreased by leaning forward or flexing the spine. A classification score using a weighted set of these criteria was developed. The proposed N-CLASS score ranged from 0 to 19 and had an area under the curve of 0.92, and the cutoff (>10/19) to obtain a specificity of >90.0% resulted in a sensitivity of 82.0%.

CONCLUSIONS:

Clinical criteria independently associated with neurogenic claudication due to LSS were identified. The use of these symptom and physical variables as a classification score for clinical research could improve homogeneity among enrolled patients.

KEYWORDS:

Cauda equina; Classification criteria; Diagnostic process; Low back pain; Lumbar spinal stenosis; Neurogenic claudication; Radicular pain

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