title: Mathematical model to estimate risk of calcium-containing renal stones.
abstract: OBJECTIVE
  Astronauts exposed to microgravity during the course of spaceflight undergo physiologic changes that alter the urinary environment so as to increase the risk of renal stone formation. This study was undertaken to identify a simple method with which to evaluate the potential risk of renal stone development during spaceflight.
  
  
  METHODS
  We used a large database of urinary risk factors obtained from 323 astronauts before and after spaceflight to generate a mathematical model with which to predict the urinary supersaturation of calcium stone forming salts.
  
  
  RESULTS
  This model, which involves the fewest possible analytical variables (urinary calcium, citrate, oxalate, phosphorus, and total volume), reliably and accurately predicted the urinary supersaturation of the calcium stone forming salts when compared to results obtained from a group of 6 astronauts who collected urine during flight.
  
  
  CONCLUSIONS
  The use of this model will simplify both routine medical monitoring during spaceflight as well as the evaluation of countermeasures designed to minimize renal stone development. This model also can be used for Earth-based applications in which access to analytical resources is limited.
authors.affiliation: Wyle Life Sciences, Houston, Tex., USA.
authors.forename: R A
authors.initials: RA
authors.lastname: Pietrzyk
authors.forename: A H
authors.initials: AH
authors.lastname: Feiveson
authors.forename: P A
authors.initials: PA
authors.lastname: Whitson
mesh_terms: D002118:Calcium / Q000032:analysis*; D002129:Calcium Oxalate / Q000032:analysis; D002130:Calcium Phosphates / Q000032:analysis; D006801:Humans; D007669:Kidney Calculi / Q000737:chemistry*; D016014:Linear Models; D015233:Models, Statistical; D015203:Reproducibility of Results; D018570:Risk Assessment; D013026:Space Flight
chemical_list: D002130:Calcium Phosphates; C485828:alpha-tricalcium phosphate; C485830:tetracalcium phosphate; D002129:Calcium Oxalate; C485838:calcium phosphate, monobasic, anhydrous; C020243:calcium phosphate; C485829:calcium phosphate, dibasic, anhydrous; D002118:Calcium