Low back pain (LBP) is one of the most common medical problems encountered in daily life; it is related to disability and work absence and accounts for high economical costs in Western societies.

Low-back pain is a diverse group of mixed pain syndromes (neuropathic and nociceptive) with different molecular pathologies at different structural levels displaying similar clinical manifestations. Currently, there are limited biomarkers (mostly imaging) or clinical findings that can be used objectively to help the physician in precise anatomic diagnosis leading to the safest and most cost-effective treatment for the patient (reduction of direct and indirect costs and improvement of treatment efficacy).

The main aim of this trial is to identify all "omics biomarkers" associated with susceptibility to chronic/persistent LBP and its different pathophysiology.

Retrospective observational multinational clinical study, with a case control design.

Investigators will compare "omic biomarkers" between patients with and without persistent chronic low back pain (CLBP).

"OMIC" biomarkers investigated will be genetics, glycomics and activomic. Genetics through GWA studies has already obtained important results in pain research; however concerning low back pain, there is not yet suitable genotype-phenotype correlations helpful to stratify patients.

Glycomics is an emerging field that has recently been identified as a priority for the next decade by the US National Academies of Science. Many common complex diseases will be associated with specific changes in glycan structures. In addition, common genetic polymorphisms influencing glycosylation and consequent differences in glycome composition could be important diagnostic and prognostic markers. The first studies reporting protein glycosylation in large human population samples have been recently published by partners in the consortium. Reliable identification of valid associations between specific glyco-phenotypes and predisposition for the development or progression of a specific disease requires analysis of thousands of patients.

Activomics: combines data about enzymatic activity of numerous numerous post-translational modification proteins in an integrated model which provides dynamic characterization of the current state of an organism. In this project information about numerous proteases, kinases, phosphatases and glycosidases will be collected and used to complement the existing phenotype information.

Inclusion Criteria of patients with persistent CLBP:

• age: older than 18;
• chronic/persistent pain (pain lasting longer than 12 weeks) between the costal margins and gluteal fold, with or without symptoms into one or both legs
• written informed consent signed;
• Caucasian ancestry

Inclusion Criteria of healthy volunteers:

• age: older than 18;
• without any chronic/persistent pain (pain lasting longer than 12 weeks) in the last one year;
• written informed consent signed;
• Caucasian ancestry

Exclusion Criteria:

• evidence of clinically unstable disease;
• severe psychiatric disorder (excluding mild depression) or mental impairment;
• recent history ( < 1 year) of spinal fracture;
• pain in the back due to spinal tumor or infection;
• pregnancy

Cases will be collected at each participating centre. Every effort will be made to accumulate a well phenotyped cohort of patients with persistent CLBP, sub-grouped into 6 categories: discogenic pain, spinal stenosis (congenital or acquired), facet joint pain, sacroiliac joint pain, low back pain with radicular pain (not predominant radicular pain) and widespread low back pain.

Controls (patients without chronic/persistent pain as defined above) will be retrieved from 2 different sources:

Existing biobanks of healthy subjects which have collected information about chronic/persistent back pain.

Subjects from the companion prospective study on acute LBP who will not have developed CLBP.

Age (decades) and gender distribution of controls will be similar to cases.