This is a prospective observational cohort multinational clinical study. There are no biomarkers to help predict in which patients acute low back pain (LBP) will transform into chronic low back pain (CLBP). Human variability and different common comorbidities complicate the picture and make stratification of patients into correct subgroups difficult. However, drugs act by targeting specific molecular pathways and are therefore efficient only in a subgroup of patients sharing common molecular pathology and common genetics. Both CLBP and disc degeneration are known to be heritable. Little investigation has taken place for genetic variants in CLBP. The main aim of this trial is to identify "omics biomarkers" associated with the transition from acute (single episode of low back pain) to persistent/chronic LBP (pain lasting more than 12 weeks).

Investigators will link and relate clinical data to a multiple "omics" analysis in patients developing persistent chronic symptoms (defined as pain that persists 3 months or more), after an episode of acute LBP. The development of persistent chronic pain will be assessed at 3 months after the acute episode.

"OMIC" biomarkers investigated will be genetics, epigenetics, glycomics and activomic.

Genetics through genome wide association studies (GWAS) 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.

Epigenetic regulation is a universal tool that higher organisms use to adapt to changes in the environment. While environmental factors, such as diet influence enzymatic processes only while they are directly present, their prolonged effects can be achieved through the cell memory of epigenetic marks. Various elements of the membrane signal transduction system were reported to be regulated by epigenetic mechanisms.

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.

"Omics" data will be compared stratifying population according to pain characteristics, pain intensity, response to treatment and duration of pain. In a subgroup of patients, "omics" data will be compared stratifying population according to pain pathophysiology: discogenic pain, spinal stenosis, facet joint pain, sacroiliac joint pain, low back pain with radicular pain (radicular pain not predominant) and widespread low back pain.

Inclusion Criteria:

• age: older than 18;
• acute episode of pain between the costal margins and gluteal fold, with or without symptoms into one or both legs lasting less than 6 weeks;
• written informed consent signed;
• Caucasian ancestry

Exclusion Criteria:

• evidence of clinically unstable disease;
• severe psychiatric disorder (excluding mild depression) or mental impairment;
• history (in the last 6 months) of persistent chronic low back pain or acute LBP episodes
• recent history (< 1 year) of spinal fracture;
• pain in the back due to spinal tumor or infection;
• pregnancy;

Each clinical centre will identify patients with an episode of acute LBP, with or without irradiation, referred from primary care physicians, orthopaedic specialists or directly selected in the emergency room (accessing hospital for acute low back pain).

The enrolment will be competitive among the participating clinical centres.