title: Kidney involvement in tuberous sclerosis complex: the impact on healthcare resource use and costs.
abstract: OBJECTIVE
  Tuberous sclerosis complex (TSC) is associated with non-malignant kidney lesions-angiomyolipomata-that may be associated with chronic kidney disease (CKD). This study investigated the relationship between renal angiomyolipomata and CKD in TSC, including the impact on healthcare resource utilization (HCRU) and costs.
  
  
  METHODS
  This was a retrospective, longitudinal cohort study based on medical record data spanning January 1990-April 2012 for 369 TSC patients treated at a specialty center in the Netherlands. Cohorts were established based on CKD stage and angiomyolipoma size. Rates of HCRU (physician visits, monitoring, and interventions) were compared across cohorts using rate ratios. Healthcare costs were compared across cohorts using cost differences. Regression models were used to identify predictive factors for HCRU and healthcare costs.
  
  
  RESULTS
  Sixteen per cent of patients reached CKD stage 3 or higher during follow-up. Patients at more advanced stages of CKD more frequently had either large or multiple small angiomyolipomata and higher HCRU rates and healthcare costs. In the multivariate analyses, male gender, CKD stage >1, angiomyolipoma size ≥3.5 cm, embolization, and the presence of moderate or severe lymphangioleiomyomatosis (LAM) were associated with greater HCRU (p ≤ 0.002 for all comparisons). Definite (vs suspected) TSC diagnosis, CKD stage 5 (vs CKD stage 1), angiomyolipoma size ≥3.5 cm, and moderate or severe LAM were associated with higher costs (p = 0.050 for TSC diagnosis, p ≤ 0.002 for other comparisons). Costs in CKD stage 5 were driven primarily by dialysis.
  
  
  CONCLUSIONS
  A substantial proportion of patients with TSC developed moderate-to-severe CKD, which was associated with renal angiomyolipomata and increased HCRU and costs.
authors.affiliation: a a Groupe d'analyse, Ltée , Montréal , QC , Canada.
authors.forename: Francis
authors.initials: F
authors.lastname: Vekeman
authors.affiliation: b b Novartis Pharmaceuticals Corporation , East Hanover , NJ , USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Magestro
authors.affiliation: c c Analysis Group, Inc. , Boston , MA , USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Karner
authors.affiliation: c c Analysis Group, Inc. , Boston , MA , USA.
authors.forename: Mei Sheng
authors.initials: MS
authors.lastname: Duh
authors.affiliation: c c Analysis Group, Inc. , Boston , MA , USA.
authors.forename: Timothy
authors.initials: T
authors.lastname: Nichols
authors.affiliation: d d Novartis Pharmaceuticals Corporation , Arnhem , The Netherlands.
authors.forename: Sahar Barjesteh
authors.initials: SB
authors.lastname: van Waalwijk van Doorn-Khosrovani
authors.affiliation: e e Department of Internal Medicine , University Medical Center Utrecht , Utrecht , The Netherlands.
authors.forename: Bernard A
authors.initials: BA
authors.lastname: Zonnenberg
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D018207:Angiomyolipoma / Q000191:economics* / Q000209:etiology / Q000473:pathology; D005260:Female; D005919:Glomerular Filtration Rate; D017048:Health Care Costs / Q000706:statistics & numerical data*; D006296:Health Services / Q000191:economics* / Q000706:statistics & numerical data; D006801:Humans; D007680:Kidney Neoplasms / Q000191:economics* / Q000209:etiology / Q000473:pathology; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D008499:Medical Records / Q000706:statistics & numerical data; D008875:Middle Aged; D009426:Netherlands; D016012:Poisson Distribution; D051436:Renal Insufficiency, Chronic / Q000191:economics* / Q000209:etiology / Q000473:pathology; D012189:Retrospective Studies; D012720:Severity of Illness Index; D017678:Sex Distribution; D014402:Tuberous Sclerosis / Q000150:complications / Q000191:economics* / Q000473:pathology; D055815:Young Adult
keywords: Chronic kidney disease; Healthcare costs; Healthcare resource utilization; Renal angiomyolipoma; Tuberous sclerosis complex