The C-reactive protein (CRP) is a marker of infection and inflammation that is raised in a large number of diseases. It is not a specific test for a particular disease and its elevated levels alert a physician to an underlying disorder. Further investigations depend on the patients history and physical examination as CRP levels increase in conditions as diverse as viral infections, auto-immune disorders or surgery. In a diagnosed chronic inflammatory disorder, its serial estimation helps in monitoring the disease as the levels fall when the inflammation subsides. Normally, the levels are < 10 mg/L while most infections/inflammations result in values higher than 100 mg/L.
Low back pain in people less than 45 years old is usually due to an injury but most such episodes resolve within 2-4 weeks. Our lower back (lumbar spine) is most at risk of developing an injury when we bend forward, twist our trunk or attempt to lift a heavy load with our hands out-stretched. Prolonged sitting or a fall too can result in it. The injury may be to a muscle, ligament, tendon, bone, or disc. Another cause can be of neural origin called sciatica. Please consult an orthopedic surgeon who can examine you and test appropriately to exclude other underlying disorder which may be the cause of pain.