Table 2 Summary of diagnostic tests for APRT deficiency and primary hyperoxaluria in the context of dialysis or kidney transplantation. (APRT: Adenine phosphoribosil transferase, AGT: alanine-glyoxylate aminotransferase, DHA: 2,8 dihydroxyadenine, FTIR: Fourier transform infrared microscopy, CKD: chronic kidney disease, ESRD: end stage renal disease). In bold *: test sufficient for diagnosis if positive

Kidney stone analysis

DHA*

nearly 100 % whewellite

any stone previously passed can be studied

stone required

DHA pathognomonic of APRT deficiency

morphology and composition (100 % 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

>0.7 mmol/1.73 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AGT activity: liver biopsy required, superseded by genetic testing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 90 % of mutations in APRT gene, >95 % in AGXT gene

cost, whole gene sequencing may be required