Laboratory diagnosis of primary hyperoxaluria (PH)

OX is a diagnostic marker for two rare, inherited metabolic diseases, primary hyperoxaluria type1 (PH1) and the usually milder, primary hyperoxaluria type 2 (PH2). PH1 is caused by a deficiency of the liver-specific peroxisomal enzyme alanine: glyoxylate transaminase (EC 2.6.1.44), while PH2 is caused by a deficiency in the cytosolic enzyme glyoxylate reductase/hydroxypyruvate reductase (EC 1.1.1.79). Both enzyme deficiencies result in increased synthesis of OX. In addition, increased level of glycolic acid is found in PH1, and L-glyceric acid in PH2. OX is eliminated by renal excretion, but because of poor solubility of calcium oxalate, deposition in the kidneys occurs. Renal failure typically develops later, followed by calcium oxalate deposition in bone, blood vessels, myocardium, and other organs.  However, as patients approach end-stage renal failure, the urine excretion of OX normalizes and the concentration of the metabolite in blood increases. 

As a consequence, the laboratory findings in patients suffering from PH changes during the course of the disease.

The quantification of OX in body fluids has been a challenge since PH was first described, mainly due to a process known as in vitro oxalogenesis. This process, resulting from a non-enzymatic conversion of other sample constituents into OX, results in an increase of OX during storage of sample, after collection. 

Many of the published analytical procedures aimed at quantification of OX in body fluids suffer from poor control of in vitro oxalogenesis, resulting in erroneously high normal ranges, while other published procedures suffers from under-quantification due to poor control of precipitation of OX-salts.   

Main goal for research project

1. Develop a fast and reliable zero in-vitro oxalogenesis analytical method for quantification of oxalic acid in blood.

2. Investigate the pre-analytical factors influencing in- vitro oxalogenesis in blood, and try to find ways (by optimizing sample preparation procedures) to control it.

3. Establish correct reference intervals of OX in blood.   

4. Re-optimise the analytical procedure for quantification of oxalic acid in urine.

5. Investigation of impact on pre-analytical factors on sample loss due to precipitation of poorly soluble salts in urine, and try to find ways (by optimizing sample preparation procedures) to control it.

6. Establish correct reference intervals in urine for children and adults.

7. Analyse samples from patients with PH.

8. Quantification of plasma-OX before, during, and after haemodialysis in patients with various renal diagnosis, including PH

9. Quantification of plasma-OX in patients admitted for kidney transplantation and subsequently at 10 weeks after transplantation in patients with renal diagnoses other than PH. The aim is to assess the magnitude of oxalate retention in these patients and to identify clinical and laboratory factors that could predict the effect of kidney transplantation on plasma concentrations of OX.