Purpose of the Study. To assess the test-retest reliability, construct validity and determine the cut-off scoret of BACKonLINE™ for people with LBP. Background. Appropriate treatment for Low back pain (LBP) is vital, however patients can wait for 14–24 weeks on NHS Physiotherapy lists. Many factors contribute to LBP and initially can be due to peripheral tissue damage. However, persistent LBP is associated with amplification in pain processing in the central nervous system (central sensitisation-CS). CS often results in poorer outcomes and often requires longer management making timely assessment and appropriate management crucial. An online self-assessment and self-management tool (BACKonLINE™) for discerning between characteristics of predominantly centrally (CD) or peripherally (PD) driven LBP was developed using a Delphi study. Method. Same subject, test-retest reliability and construct validity study (two sessions). Sample of 35 volunteers with LBP. In session 1, participants completed BACKonLINE™ and validated questionnaires (Oswestry Disability Index, StartBack, Tampa scale for Kinesiophobia, Pain Anxiety Symptom Scale Short Form 20). Participants repeated the process one week later. BACKonLINE's Cut-off score was determined by plotting results against StartBack using ROC curve analysis. Results. BACKonLINE™ showed excellent test-retest reliability (ICC= 0.913; 95%CI=0.832–0.956). When assessing construct validity, the aforementioned questionnaires demonstrated moderate correlation with BACKonLINE™ (Pearson's r range= 0.42–0.67, p-value<0.005). ROC analysis determined that scores higher than 42 in BACKonLINE™ indicate CD LBP while scores ≤42 indicate PD LBP. Conclusion. The study shows that BACKonLINE™ has excellent test-retest reliability, and good construct validity within a LBP population. However, further studies with larger sample sizes should be conducted before the implementation of BACKonLINE™. Conflicts of interest: No conflicts of interest. Sources of funding: Civil Service Commission, Kuwait