S11.2 INVESTIGATIONS ON BLOOD TO DIAGNOSE SUBTLE INFECTION AND DETERMINE DEFINITIVE ERADICATION OF INFECTION

Abstract

I studied 1191 patients with known or suspected bone or joint infection. I divided patients with acute onset infection into three groups based on the speed of onset and the intensity of the infection. I divided the patients with known chronic infection into four groups according to the intensity of the infection. I used clinical and radiological parameters to determine the groups. There was a fifth group of patients with suspected infection who turned out to have other related or similar pathology but who were actually free of infection. The laboratory tests studied were all the parameters constituting a full blood count (CBC), tests of inflammatory activity (erythrocyte sedimentation rate, C-reactive protein, plasma viscosity and procalcitonin). I also studied the iron profile (serum iron, iron saturation, transferrin and ferritin). The same tests were used to monitor the patient’s progress as they responded to treatment – or not.

Findings: Not surprisingly those patients with the most intensive and extensive infection had disturbances across the spectrum of tests. As the intensity and extent of infection diminished more and more parameters returned to normal. It is thus possible to titrate the systemic effects of infection. Contrary to popular belief the white cell count, differential count and the activity tests can be normal in a large number of patients with recognisable infection. The most subtle evidence of infection is found in the iron profile, namely a diminished serum iron with an elevated ferritin level. Indeed the most definitive indicator of infection is the ratio of ferritin to iron.