title: Validity of diagnostic coding for undernutrition in hospitals.
abstract: OBJECTIVE
  We examined the accuracy of ICD-10 diagnostic coding for undernutrition in Danish Hospitals, including the use of Nutritional Risk Screening 2002 guidelines.
  
  
  METHODS
  We investigated a random sample of hospitalized patients registered in the Danish National Registry of Patients with a discharge diagnosis of undernutrition between 2002 and 2011 in the North Denmark Region. Based on medical record review we estimated the positive predictive value (PPV) of the undernutrition diagnosis. Stratification was made by calendar period, hospital type (local vs. university), gender, age, speciality and type of diagnosis code. Subsequently, we evaluated the use of Nutritional Risk Screening 2002 as recommended by the European Society of Clinical Nutrition and Metabolism and the Danish National Board of Health.
  
  
  RESULTS
  We could retrieve the medical records of 172/200 sampled patients with undernutrition (86%). Nineteen patients were classified as being definite (screening-confirmed) cases and another 103 patients as probable (clinically-confirmed) cases of undernutrition, yielding a PPV of 11.0% (95% confidence interval [CI]: 6.8-16.7) for definite undernutrition and 70.9% (95% CI: 63.5-77.6) for any confirmed undernutrition. Only 26.2% of patients coded with undernutrition had been screened according to the Nutritional Risk Screening 2002.
  
  
  CONCLUSIONS
  This population-based study found modest agreement between ICD-10 codes for undernutrition compared to a standard method (Nutritional Risk Screening 2002) as documented in medical doctors' records in Danish hospitals. Diagnoses of undernutrition contained in hospital discharge registries should be used with caution.
authors.affiliation: Faculty of Health Sciences, Aarhus University, Denmark. Electronic address: nicklas_r@hotmail.com.
authors.forename: Nicklas Højgaard
authors.initials: NH
authors.lastname: Rasmussen
authors.affiliation: Department of Clinical Epidemiology, Institute of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Reimar Wernich
authors.initials: RW
authors.lastname: Thomsen
authors.affiliation: Centre for Nutrition and Bowel Diseases, Department of Medical Gastroenterology, Aalborg University Hospital, Aalborg, Denmark; Department of Clinical Medicine, Faculty of Medicine, Aalborg University, Aalborg, Denmark.
authors.forename: Henrik Højgaard
authors.initials: HH
authors.lastname: Rasmussen
authors.affiliation: Department of Clinical Epidemiology, Institute of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Mette
authors.initials: M
authors.lastname: Søgaard
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059019:Clinical Coding; D003718:Denmark; D005260:Female; D006760:Hospitalization; D006761:Hospitals; D006801:Humans; D038801:International Classification of Diseases / Q000592:standards*; D008297:Male; D044342:Malnutrition / Q000175:diagnosis*; D008499:Medical Records; D008875:Middle Aged; D010351:Patient Discharge; D011237:Predictive Value of Tests; D012042:Registries; D015203:Reproducibility of Results; D055815:Young Adult
keywords: Danish National Registry of Patients; Nutritional screening guidelines; Positive predictive value; Undernutrition; Validation