title: The value of measuring urinary β2-microglobulin and serum creatinine for detecting tubulointerstitial nephritis and uveitis syndrome in young patients with uveitis.
abstract: OBJECTIVE
  Tubulointerstitial nephritis and uveitis (TINU) syndrome is characterized by tubulointerstitial and ocular inflammation. Thus far, the value of noninvasive diagnostic tests is not known.
  
  
  OBJECTIVE
  To determine whether urinary β2-microglobulin (β2M), urinary protein, and serum creatinine have predictive value for detecting TINU syndrome in young patients with uveitis.
  
  
  METHODS
  This prospective cohort study was conducted July 2010 through February 2013 at a tertiary care referral center in Utrecht, the Netherlands. Forty-five consecutive new patients with uveitis aged 22 years or younger were enrolled.
  
  
  METHODS
  Urinary β2M, urinary protein, and serum creatinine were measured prospectively, and the estimated glomerular filtration rate was calculated.
  
  
  METHODS
  A post hoc analysis was performed to determine whether urinary β2M, urinary protein, serum creatinine, estimated glomerular filtration rate, and/or pyuria were correlated with definitive and probable cases of TINU syndrome.
  
  
  RESULTS
  Eighteen of the 45 patients (40%) in our cohort had elevated urinary β2M levels, and 10 patients (22%) had elevated serum creatinine levels. Twenty of 43 patients (47%) had proteinuria. Eight of the 45 patients were diagnosed by a pediatric nephrologist as having renal dysfunction that suggested acute interstitial nephritis. Of these 8 patients, 2 were definitively diagnosed as having TINU syndrome (confirmed by renal biopsy). After excluding other causes of renal dysfunction, the remaining 6 patients with uveitis and renal dysfunction fulfilled the criteria of probable TINU syndrome. The 8 patients with definitive or probable TINU syndrome had higher urinary β2M levels than patients with normal renal function (median β2M, 1.95 mg/L; 95% CI, 1.26-5.16 mg/L vs 0.20 mg/L; 95% CI, 0.19-0.21 mg/L; P < .001; Mann-Whitney U test). Our analysis revealed that the positive predictive value of increased β2M combined with increased serum creatinine was 100% for detecting definitive and/or probable TINU syndrome.
  
  
  CONCLUSIONS
  These data suggest that urinary β2M and serum creatinine levels are sensitive and relatively simple diagnostic screening tools for detecting renal dysfunction to diagnose TINU syndrome in young patients with uveitis similar to those evaluated in this study.
authors.affiliation: Department of Ophthalmology, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Ymkje M
authors.initials: YM
authors.lastname: Hettinga
authors.affiliation: Department of Ophthalmology, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Laura M E
authors.initials: LM
authors.lastname: Scheerlinck
authors.affiliation: Department of Pediatric Nephrology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Marc R
authors.initials: MR
authors.lastname: Lilien
authors.affiliation: Department of Ophthalmology, Erasmus Medical Center Rotterdam, Rotterdam, the Netherlands.
authors.forename: Aniki
authors.initials: A
authors.lastname: Rothova
authors.affiliation: Department of Ophthalmology, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Joke H
authors.initials: JH
authors.lastname: de Boer
mesh_terms: D000293:Adolescent; D015415:Biomarkers / Q000097:blood / Q000652:urine; D001706:Biopsy; D002648:Child; D002675:Child, Preschool; D003401:Creatine / Q000097:blood*; D003937:Diagnosis, Differential; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007668:Kidney / Q000473:pathology; D008297:Male; D009395:Nephritis, Interstitial / Q000150:complications* / Q000175:diagnosis / Q000378:metabolism; D011446:Prospective Studies; D012720:Severity of Illness Index; D013577:Syndrome; D014605:Uveitis / Q000175:diagnosis / Q000209:etiology* / Q000378:metabolism; D055815:Young Adult; D001613:beta 2-Microglobulin / Q000652:urine*
chemical_list: D015415:Biomarkers; D001613:beta 2-Microglobulin; D003401:Creatine