title: The beta2-microglobulin/cystatin C ratio--a potential marker of post-transplant lymphoproliferative disease.
abstract: BACKGROUND
  As a consequence of more intensified immunosuppression, post-transplant lymphoproliferative disease (PTLD) is increasingly observed in patients after solid-organ transplantation. Beta2-microglobulin, a low-molecular weight protein (MW 11.8 kDa), is produced by all nucleated cells as part of the HLA complex. Its serum concentration is directly correlated with prognosis in patients with lymphatic neoplasms. Like other low-molecular weight proteins, beta2-microglobulin is eliminated by glomerular filtration. This complicates its use as a tumor marker in renal insufficiency. Cystatin C, a low-molecular weight protein of 13.3 kDa, is a new marker of kidney function largely unaffected by extrarenal disease. We, therefore, sought to assess the potential of the beta2-microglobulin/cystatin C ratio (beta2M/Cys) as a marker of lymphoproliferation.
  
  
  METHODS
  Beta2M/Cys was determined by particle-enhanced immunonephelometry in sera from 132 children with different degrees of renal insufficiency, 5 of whom had lymphoproliferative disease. Renal function was assessed using the Schwartz formula.
  
  
  RESULTS
  Beta2M/Cys was constant between 1.2 and 2.4 mg/mg for Schwartz GFR > or = 40 ml/min x 1.73 m2. With lower GFR, beta2M/Cys rose progressively, maximum values being found in the hemodialysis patients (4.85-11.73). Healthy renal transplant recipients had beta2M/Cys comparable to controls. With acute lymphoproliferative disease, all but one patient had significantly elevated beta2M/Cys between 2.68 and 3.68 mg/mg, which returned to normal in remission (1.67-2.35 mg/mg). The sensitivity of a beta2M/Cys ratio > 2.4 mg/mg for the detection of PTLD was 80%, the specificity 100%, positive predictive value 100%, negative predictive value 90%.
  
  
  CONCLUSIONS
  The beta2-microglobulin/cystatin C ratio is a promising parameter of lymphoproliferation in patients with normal or mildly impaired renal function.
authors.affiliation: Medical Center of Bonn University, The Children's Hospital, Bonn, Germany. bokenkamp@compuserve.com
authors.forename: A
authors.initials: A
authors.lastname: Bökenkamp
authors.forename: A
authors.initials: A
authors.lastname: Grabensee
authors.forename: B
authors.initials: B
authors.lastname: Stoffel-Wagner
authors.forename: C
authors.initials: C
authors.lastname: Hasan
authors.forename: T
authors.initials: T
authors.lastname: Henne
authors.forename: G
authors.initials: G
authors.lastname: Offner
authors.forename: M J
authors.initials: MJ
authors.lastname: Lentze
mesh_terms: D015415:Biomarkers / Q000097:blood; D002648:Child; D055316:Cystatin C; D015891:Cystatins / Q000097:blood*; D005260:Female; D006801:Humans; D016030:Kidney Transplantation; D016014:Linear Models; D008232:Lymphoproliferative Disorders / Q000097:blood / Q000175:diagnosis*; D008297:Male; D011183:Postoperative Complications / Q000175:diagnosis*; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D001613:beta 2-Microglobulin / Q000097:blood*
chemical_list: D015415:Biomarkers; C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D001613:beta 2-Microglobulin