High Prevalence of Neuropathic Pain Component in Patients with Low Back Pain : Evidence from Meta-Analysis

BACKGROUND: Low back pain (LBP) is a complex syndrome which includes a nociceptive (NcP) component, a neuropathic (NeP) component, or a mixture of components (mixed pain). The NeP component (NePC) in LBP is defined as the presence of NeP with or without an NcP. OBJECTIVE: This meta-analysis aimed at assessing the pooled prevalence of NePC in patients with LBP and at identifying the factors causing significant heterogeneity in reported prevalence. STUDY DESIGN: Meta-analysis. METHODS: A systematic literature search was carried out, with inclusion of all epidemiological studies describing the NeP prevalence levels in LBP patients while using standard diagnostic methods. The "pooled prevalence rate (PPR)" of NePC, either on its own or in combination with NcP, was calculated. A pre-specified subgroup analysis was carried out, considering LBP duration, presence of leg pain, diagnostic method(s), and questionnaire(s) used. RESULTS: The meta-analysis included 20 studies relating to a total of 14,269 LBP patients, of whom 7,969 patients (55.8%) were identified as presenting with NePC. The pooled PR (95% CI) of NePC in patients with LBP was 0.47 (0.40 - 0.54), while the pooled PR of NcP was 0.56 (0.48 - 0.63). Higher NePC pooled PR values were identified in LBP with leg pain as compared to uncomplicated LBP (respectively: 0.60; 0.47 - 0.73 vs 0.27; 0.23 - 0.31; Pinteraction < 0.01). LIMITATIONS: The quality of the included studies was assessed using ad-hoc criteria. Due to the limited number of available studies, one may need to be cautious in reaching conclusions about the impact of disease duration on NePC prevalence values. We pooled studies which used a range of different diagnostic methods, with putatively different sensitivity/specificity diagnosing levels. CONCLUSIONS: Overall, high NePC prevalence levels were here identified in LBP patients. As the pain is a subjective phenomenon and there is no gold standard for the diagnosis of NePC, there is the possibility that the pooled effect estimate may alter depending upon the diagnostic method used. KEY WORDS: Neuropathic pain, nociceptive pain, low back pain, symptom-based questionnaire, chronicity.