Table 2.

Biochemical factors associated with occult urinary stones.

Variable	N	Normal Range	Whole Cohort	Occult urinary stones present	Occult urinary stones absent	p-value
Serum calcium, mg/dl	96	8.4–9.8	10.5 ± 0.5	10.6 ± 0.5	10.4 ± 0.5	0.26
Parathyroid hormone, pg/ml*	96	14–64	78.5 (61.5–106.0)	85.5 (53.4–106.1)	78.0 (63.5–106.0)	0.92
Phosphorus, mg/dl	96	2.5–4.5	3.2 ± 0.5	3.1 ± 0.6	3.3 ± 0.5	0.44
25-hydroxyvitamin D, ng/dl	95	30–100	31.1 ± 12	31.3 ± 10	31.0 ± 12	0.91
1,25-dihydroxyvitamin D, pg/ml	28	16–65	76.0 ± 22	90.7 ± 20	70.1 ± 20	0.02
Urine calcium excretion (mg/24 hours)	89	Female <250 Male <300	245 ± 136	327 ± 142	223 ± 126	0.002
Urine calcium excretion (mg/kg/24 hours)	89	<4mg/kg/day	3.47 ± 1.89	4.54 ± 2.09	3.18 ± 1.73	0.005
24 hour urine creatinine (g/24 hours)	81	0.8–1.8	1.19 ± 0.40	1.41 ± 0.44	1.13 ± 0.38	0.01
24 hour urine volume (ml/24 hours)	88		2173 ± 1145	2618 ± 1803	2014 ± 882	0.05
Estimated glomerular filtration rate, ml/min	96	>60	80.9 ± 16	80.2 ± 13	81.1 ± 17	0.83

Values represent mean ± SD;

^*PTH is shown as median and interquartile range