Clinical trial NCT02120105: Cystine Capacity Clinical Study (CysCap)
Official title: Cystine Capacity Clinical Study (CysCap)
Study type: OBSERVATIONAL
Overall status: COMPLETED
Conditions: Cystinuria
Keywords: Renal aminoaciduria
cystinuria
D-penicillamine
renal tubular transport
inborn errors
tiopronin
urolithiasis
Lead sponsor: NYU Langone Health
Sponsor class: OTHER
First posted: 2014-04-22
Enrollment: 30
Sex: ALL
Minimum age (years): 8
Maximum age (years): 80
Standard ages: CHILD
ADULT
OLDER_ADULT
Accepts healthy volunteers: no
Observational model: CASE_ONLY
Time perspective: PROSPECTIVE
Sampling method: NON_PROBABILITY_SAMPLE
Study population: For patients to be enrolled in this study they must have a diagnosis of cystinuria.

Brief summary: The purpose of this study is to determine whether urinary cystine capacity, an assay used to measure the amount of cystine in the urine, can be used to predict stone recurrence in patients with cystinuria.

Detailed description: Cystinuria is a rare genetic cause of kidney stones that leads to significant morbidity due to the recurrent nature of the disease. Despite recent advancements in knowledge about cystinuria, such as the discovery of the genetic defects that cause the disease, there have been very few studies of clinical determinants of recurrent stone formation. An optimal method of measuring cystine solubility in the urine has been lacking, and therefore response to pharmacologic and dietary therapy is often not known. Recently, a new assay to measure the amount of cystine in the urine was developed called Cystine Capacity, or CysCap. It is an assay that adds a pre-formed amount of cystine crystals to urine and measures the amount of cystine the urine can take up from the solid phase (in undersaturated urine) or gives up to solid phase (in supersaturated urine). This study seeks to examine how well this measure of urinary cystine predicts stone occurrence, with the ultimate goal of helping to guide therapy and preventing kidney stones in cystinurics.

This is an observational study over 3 years. Subjects who are enrolled in the study will perform semi-annual 24-hour urine collections. They will undergo imaging of the kidneys every 6 months to monitor kidney stone formation or growth, in order to correlate urinary parameters with clinical events. The study will examine how well the urinary cystine capacity predicts stone formation.

Eligibility criteria: Inclusion Criteria:

* Patients with a confirmed laboratory diagnosis of cystinuria will be included in this study. There will be no age barrier to inclusion, but included patients must be able to reliably collect urine for 24 hours. Men and women will be recruited equally and there are no restrictions for racial or ethnic origin in this study.
* Patient enrollment will require signing of an informed consent document approved by the Lenox Hill IRB.
* For children 8-18 years of age, signing an assent to participate will also be required.

Exclusion Criteria:

* Patients will be excluded if they cannot sign consent or assent.
* Furthermore if the patient cannot reliably collect urine for 24 hours or adhere to study follow up visit requirements.

Primary outcomes:
measure: Cystine capacity will be correlated with recurrence or non-recurrence of stones
timeFrame: every 6 months over 3 years
Secondary outcomes:
measure: 24-hour urine cystine excretion
timeFrame: every 6 months over 3 years
measure: episodes of renal colic and/or stone passage from a kidney that was previously stone-free
timeFrame: every 6 months over 3 years
measure: Evidence of new asymptomatic stones noted on the contralateral kidney
timeFrame: every 6 months over 3 year observational study
Other outcomes:
Locations:
city: New York
country: United States
facility: NYU Langone Medical Center
state: New York
Study officials:
affiliation: NYU Langone Health
name: David S Goldfarb, MD
role: PRINCIPAL_INVESTIGATOR
References:
citation: Goldfarb DS, Coe FL, Asplin JR. Urinary cystine excretion and capacity in patients with cystinuria. Kidney Int. 2006 Mar;69(6):1041-7. doi: 10.1038/sj.ki.5000104.