Low molecular mass proteins as markers for renal function and dialysis efficiency

Kidney disease is a growing problem in the whole world. It is important to find these patients in an early state of the disease because then they can be treated and dialysis treatment can be avoided. To measure the glomerular filtration rate (GFR) an invasive technigue is used. In this thesis an equation to estimate GFR (eGFR) by drawing a blood sample and measure the concentration of cystatin C is presented. This equation is the first one working both for adults and children. To establish an equation working at all laboratories, primary and secondary reference preparations for cystatin C were developed. The secondary reference preparation will be used to establish an international calibrator, which can be used by the diagnostic companies to establish an uniform value of cystatin C.
Cystatin C has been proposed to be a marker of inflammation. In our study of patients, without any prior inflammation, who undergo elective surgery, the concentration of cystatin C was unaltered while an increase in the concentration of CRP was seen. This result shows that cystatin C is not a marker of inflammation.
Three different types of dialysis treatments (haemodialysis, haemofiltration, haemodiafiltration) were tested for their capacity to remove low molecular mass proteins (LMMP) and thus their potential for treatment of patients with kidney failure. The LMMP have been proposed to be uraemic toxins and must therefore be removed from the circulation. The result from our study showed that cystatin C, β2-microglobulin and β-trace protein can be used as markers for the efficiency of haemofiltration (HF) and haemodiafiltration (HDF). The elimination pattern of β-trace protein differs between HDF and HF and the free proteins might therefore be useful markers in the evaluation of different convective therapies.