title: Thrombocytopenia on the first day of emergency department visit predicts higher risk of acute kidney injury among elderly patients.
abstract: BACKGROUND
  Few studies have addressed risk factors for acute kidney injury (AKI) in geriatric patients. We investigated whether thrombocytopenia was a risk factor for AKI in geriatric patients with medical illnesses.
  
  
  METHODS
  A prospective cohort study was conducted, by recruiting elderly (≥65 years) patients who visited the emergency department (ED) for medical illnesses during 2014. They all received hemogram for platelet count determination, and were stratified according to the presence of thrombocytopenia (platelets, <150 K/μL) during their initial ED evaluation. They were prospectively followed up during their ED stay. We analyzed the relationship between the diagnosis of thrombocytopenia and subsequent AKI after ED stay, using Cox proportional hazard modeling, with platelet count as a continuous variable or thrombocytopenia as a categorical variable.
  
  
  RESULTS
  Of 136 elderly patients (mean age of 80.7 ± 8.2 years, 40% with chronic kidney disease, and 39% with diabetes) enrolled, 22.8% presented with thrombocytopenia, without differences in baseline renal function. After a mean ED stay of 4.4 ± 2.1 days, 41.9% developed AKI (52.6% Kidney Disease Improving Global Outcomes [KDIGO] grade 1, 24.6% grade 2, and 22.8% grade 3). Patients with higher AKI severity had stepwise lower platelet counts compared to those without AKI. The Cox proportional hazard model revealed that lower platelet count as a continuous variable (hazard ratio [HR] 0.984, 95% confidence interval [CI] 0.975-0.994) and as a categorical variable (presence of thrombocytopenia) (HR 1.86, 95% CI 1.06-3.27) increased the risk of AKI. The sensitivity analyses accounting for nephrotoxic medications use, including non-steroidal anti-inflammatory drugs, vancomycin, and contrast, yielded similar results.
  
  
  CONCLUSIONS
  Thrombocytopenia is common among ED-visiting elderly, and the potential relationship between platelet counts and the risk of AKI suggests the utility of checking hemogram for those at-risk ofdeveloping adverse renal events.
  
  
  CONCLUSIONS
  Thrombocytopenia on initial presentation might indicate an increased risk of AKI among elderly patients with medical illnesses.
authors.affiliation: Department of Medicine, National Taiwan University Hospital Jinshan Branch, New Taipei City, Taiwan.|Graduate Institute of Toxicology, National Taiwan University College of Medicine, Taipei, Taiwan.|Division of Nephrology, Department of Internal Medicine, National Taiwan University Hospital, 7 Chung-Shan South Road, Taipei, 100, Taiwan.
authors.forename: Chia-Ter
authors.initials: CT
authors.lastname: Chao
authors.affiliation: Department of Traumatology, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Hung-Bin
authors.initials: HB
authors.lastname: Tsai
authors.affiliation: Graduate Institute of Toxicology, National Taiwan University College of Medicine, Taipei, Taiwan.|Department of Integrative Diagnostics and Therapeutics, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Chih-Kang
authors.initials: CK
authors.lastname: Chiang
authors.affiliation: Division of Nephrology, Department of Internal Medicine, National Taiwan University Hospital, 7 Chung-Shan South Road, Taipei, 100, Taiwan. 007378@ntuh.gov.tw.
authors.forename: Jenq-Wen
authors.initials: JW
authors.lastname: Huang
mesh_terms: D058186:Acute Kidney Injury / Q000175:diagnosis*; D000368:Aged; D000369:Aged, 80 and over; D004636:Emergency Service, Hospital; D005260:Female; D006801:Humans; D007677:Kidney Function Tests; D008297:Male; D010976:Platelet Count; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D013921:Thrombocytopenia / Q000175:diagnosis*
keywords: Acute kidney injury; Elderly; Emergency department; Geriatrics; Platelets; Thrombocytopenia