Table 1.

Characteristics of patients identified with APRT deficiency and tests used for diagnosis (alone or in combination)

Characteristic	Value
No. of families	43
No. of patients	53
<16 years (n [%])	20 (37.7)
>16 years (n [%])	33 (62.3)
Male gender (n [%])	34 (64.1)
Age at diagnosis (years; median [IQR])	36.3 (6.4 to 50.5)
Tests leading to diagnosis (n [%])
stone analysis	31 (58.5)
crystalluria	15 (28.3)
renal biopsy	6 (11.3)
native kidney	2 (3.8)
transplant	3 (5.7)
both	1 (1.9)
APRT activity (overall)	41 (77.4)
APRT activity in asymptomatic	2 (3.8)

For some patients, several diagnostic tests were simultaneously performed (e.g., crystalluria and stone analysis). For five patients, diagnosis was made directly by APRT activity measurement in the setting of familial screening. IQR, interquartile ratio.