| APRT deficiency | Primary hyperoxaluria type 1 | Advantages | Limitations |
---|---|---|---|---|
Kidney stone analysis | DHA* | nearly 100Â % whewellite | any stone previously passed can be studied | stone required |
DHA pathognomonic of APRT deficiency | ||||
morphology and composition (100Â % whewellite) suggestive of primary hyperoxaluria | ||||
Crystalluria | DHA* | calcium oxalate (whewellite) | DHA pathognomonic of APRT deficiency | not feasible in anuric patients |
whewellite crystalluria may suggest primary hyperoxaluria (unspecific) | rare false negative in ESRD patients | |||
FTIR/kidney biopsy | DHA* | calcium oxalate (whewellite) | characterization of crystals in kidney biopsy | kdney biopsy required |
highly sensitive and specific | limited availability | |||
Urinary oxalate | Â | >0.7Â mmol/1.73Â m2/day suggests primary hyperoxaluria | availability, easy to perform | no clear cut-off |
may be normal in patients with advanced CKD | ||||
Plasma oxalate |  | >30 to 50 μmol/l suggests primary hyperoxaluria | availability, easy to perform | no clear cut-off |
useless in patients without advanced CKD | ||||
Enzyme activity | decreased APRT activity in erythrocyte lysates* | decreased AGT activity in hepatocytes* | highly sensitive and specific | AGT activity: liver biopsy required, superseded by genetic testing |
APRT activity: not reliable after blood transfusion, limited availability | ||||
Molecular study | mutations in APRT gene (two alleles)* | mutations in AGXT gene (two alleles)* | identification of 90Â % of mutations in APRT gene, >95Â % in AGXT gene | cost, whole gene sequencing may be required |