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Table 3 Validation of diagnoses in the Swedish Inpatient Register by Positive Predictive Values (PPVs)

From: External review and validation of the Swedish national inpatient register

Diagnosis Correct diagnosis in the IPR (%) = positive predictive value (PPV) Comment Main Author PubMed ID Year Gold Standard (reference)
Cardiovascular disease
Myocardial infarction 36/36 (100) Only primary diagnoses were evaluated.
NPV = 861/864 (99.7)
Nilsson [7] 8114596 1994 MR
Myocardial infarction 2053/2101 (98) Patients aged 45 - 70 years in 1992 - 1994. Linnersjö[34] 11121592 2000 MR
Angina Pectoris 18/19 (95) Only primary diagnoses were evaluated.
NPV = 879/881 (99.8)
Nilsson [7] 8114596 1994 MR
Heart failure (HF) 259/317 (81.7) Definition of HF proposed by the European Society of Cardiology [35].
Restricting the diagnosis HF to the primary diagnosis, then 133/140 (95.0%) were correct.
Ingelsson [36] 15916919 2005 ULSAM
Heart failure 15/17 (88) Only primary diagnoses were evaluated.
NPV = 876/883 (99.2)
Nilsson [7] 8114596 1994 MR
Atrial fibrillation (using ICD-codes for atrial fibrillation or atrial flutter) 97/100 (97) 95 individuals had ECGs consistent with atrial fibrillation. Two patients had no ECGs available but were regarded as having atrial fibrillation on the basis of medical records. Smith [37] 19936945 2009 MR + Electrocardiograms (ECG)
Non-fatal strokes 3492/5101 (68.5) Patients aged 25-74 years in 1985-89. Criteria for acute stroke in this study were based on WHO criteria. Stegmayr [38] 1291884 1992 MONICA-population based stroke register
Stroke/Transient ischemic Attack 207/210 (98.6) ULSAM Wiberg   (PC, Feb 12) ULSAM
Gestational hypertension 108/111 (97.3)   Zetterström   (PC, March 3) MR
Gestational hypertension 97/115 (84.3)   Ros [39] 9620050 1998 MR
Vascular interventions (for lower limb ischemia) 545/546 (99.8)   Hultgren [40] 11170873 2001 MR
Autoimmune/immune-mediated diseases
Rheumatoid arthritis (RA) 489/510 (95.9) Malmö, Sweden, 1990-1994. According to the RA criteria of the American College of Rheumatology [41]. Turesson [42] 10461483 1999 MR
Rheumatoid arthritis Without lymphoma: 440/505 (87.1)
With lymphoma: 386/413 (93.5)
In 40 of the 386 cases with lymphoma, medical records did not include enough information to evaluate whether the RA criteria of the American College of Rheumatology were fulfilled but all available information supported the diagnosis of RA Baecklund [22] 16508929 2006 MR
Wegener's granulomatosis 68/78 (87) American College of Rheumatology diagnostic criteria [43] Knight [12] 12115591 2002 MR
Celiac disease 66/77 (86) of patients with later lymphoma Only in 8 patients could celiac disease be ruled out. In 3 patients, the chart reviews were consistent with possible celiac disease. Ekström-Smedby [44] 15591504 2005 MR
Primary adrenocortical insufficiency 105/133 (78.9)   Bensing [45] 18727712 2008 Patients tested positive for 21-OH autoantibodies
Diabetes mellitus (type 1 and 2)* 22/28 (79) Only primary diagnoses were evaluated.
NPV = 872/872 (100)
Nilsson [7] 8114596 1994 MR
Both diabetes (type 1 or 2) and foot ulcer* 235/236 (99.6) admissions were correct with regards to ICD-coding 117 patients with deep foot infections and type 1 or 2 diabetes, who had been referred to a multidisciplinary foot-care team at Lund University Hospital. Ragnarson-Tennvall [46] 11123504 2000 MR
Inflammatory bowel disease (IBD) 4778/6440 (74) 1965-1983.
Due to the ICD-classification used at this time, ulcerative colitis could not be distinguished from Crohn's disease, and therefore "overall IBD" was evaluated
Ekbom [47] 1985033 1991 MR + histopathological reviews
Psychiatric disease and neurology
Schizophrenia 94/100 (94.9) Review of medical records with structured diagnostic interviews Ekholm [48] 16316898 2005 MR
Schizophrenia 78/91 (85.7) Individuals born 1973-77.
DSM-IV criteria for schizophrenia syndrome
Dalman [49] 12395142 2002 MR
Schizophrenia 106/111 (95.5) Review of 121 consecutive cases in one city using a structured DSM-IV checklist, 111 records obtained Hultman [50] 16863597 2006 MR
Schizophrenia,
schizophreniform disorder or schizoaffective disorder
94/168 (56) Primary diagnoses that fulfilled DSM-IV criteria (OPCRIT algorithm) Reutfors [51] - 2009 MR
Schizophrenia † 78/104 (75.0)
to
85/104 (81.7)
104 patients discharged in 1971 with a diagnosis of schizophrenia. DSMIII-criteria were used for this validation. From Stockholm County IPR. A strict review found a PPV of 75%. This figure increased to 85% when some lack of information was accepted (less strict criteria). Kristjansson [52] - 1987 MR
Schizophrenia (Kappa = 0.37 correlating to an agreement rate of 68%) All individuals with a diagnosis of schizophrenia in the IPR and who had an inpatient forensic psychiatric assessment using a national register of all such evaluations from 1988-2000 (n = 1638). Fazel [25] 19454640 2009 Forensic psychiatric assessment
Schizophrenia 34/44 (77%)   Bergman [53] - 1999 Four-week- inpatient assessment in forensic psychiatry department
Alzheimer 54/75 (72)   Jin [54] 15326258 2004 Clinical work-up following phone interview
Personality disorders 37/40 (92) Random sample of 40 individuals out of 401 violent offenders with personality disorders from a longitudinal study Grann [55] - 1998 MR
Personality disorders 30/55 (55%)   Bergman [53] - 1999 Four-week- inpatient assessment in forensic psychiatry department
Guillain-Barré Syndrome (GBS) 69/83 (83) 83% of patients fulfilled the National Institute of Neurological and Communicative Disorders and Stroke criteria for GBS [56]. PPV of first primary diagnosis with GBS was 84%; and for secondary diagnosis 75%. Jiang [57] 7785420 1995 MR
Herpes simplex encephalit 223/638 (35.0) 1990-2001 Hjalmarsson [58] 17806053 2007 Laboratory data (positive finding of HSV-1)
Trauma and fractures
Brain concussion 18/18 (100) Only primary diagnoses were evaluated.
NPV = 880/882 (99.8)
Nilsson [7] 8114596 1994 MR
Hip fracture 21/22 (95) Only primary diagnoses were evaluated.
NPV = 877/878 (99.9)
Nilsson [7] 8114596 1994 MR
Hip fracture 2556/2597 (98.4) Cases derived both from IPR and operation registers. Michaelsson [59] 9632404 1998 MR
Injuries 1299/1370 (94.8) Injury code was correct at 3-digit-level. Gedeborg - (PC, Feb 3) MR
Surgical procedures (and related medical conditions)
Major amputations (leg and arm) 610/624 (97.8) Unique number of amputations was 610 in 624 patients. Malmstedt   (PC, Feb 24) MR
Appendicitis† 1661/1840 (90.3) Performed in the Jönköping county. Incidental appendectomies were excluded. The IPR overestimated the prevalence of appendicitis with 6%. The negative predictive value of appendicitis was 94.0% and the accuracy 91.3%† Andersson [60] 8298378 1994 Histological examination of excised tissue (in patients undergoing appendectomy)
Inguinal hernia 17/18 (94) Only primary diagnoses were evaluated.
NPV = 882/882 (100)
Nilsson [7] 8114596 1994 MR
Other disorders
Achalasia 67/83 (81)   Zendehdel [61] 17488250 2007 MR
Prostate hyperplasia 14/14 (100) Only primary diagnoses were evaluated.
NPV = 882/886 (99.5)
Nilsson [7] 8114596 1994 MR
Asthma 14/15 (93) Only primary diagnoses were evaluated.
NPV = 885/885 (100)
Nilsson [7] 8114596 1994 MR
Abdominal pain (observation for abdominal pain) 33/37 (89) Only primary diagnoses were evaluated.
NPV = 860/863 (99.7)
Nilsson [7] 8114596 1994 MR
Preeclampsia 137/148 (92.6)   Ros [39] 9620050 1998 MR
Endometriosis Without ovarial cancer: 615/628 (97.9% correct).
With ovarial cancer: 220/225 (97.8% correct)
  Melin - (PC, Feb 3) MR
Foot ulcer (only) 249/250 (99.6) admissions to hospital were correct with regards to ICD-coding Based on 117 patients with deep foot infections and type 1 or 2 diabetes, referred to multidisciplinary foot-care team. Specificity for foot ulcers and concomitant diabetes was 98%. Ragnarson-Tennvall [46] 11123504 2000 MR
Connective tissue disease (CTD) 71/91 (78%) In this study CTD included rheumatoid arthritis, systemic lupus erythemathosus, sclerodermia, Sjögren's syndrome, dermatomyositis, polymyositis etc. Nyren [62] 9492663   MR
Acute pancreatitis 695/602 (98.8) Among 602 patients with a primary or secondary diagnosis of acute pancreatitis in the IPR. 84.0% had a definitive acute pancreatitis and another 14.8% a probable acute pancreatitis. Lindblad   (PC, Feb 6) MR + laboratory tests and radiological imaging
  1. PC, Personal communication: All personal communications took place in 2010 (exact date is listed in the table).
  2. CDT, Connective tissue disease. GBS, Guillain-Barré Syndrome; HF, Heart Failure, IBD, Inflammatory bowel disease. IPR, Inpatient Register.
  3. MR, compared with Medical Records (patient charts).
  4. PPV, Positive Predictive Value.
  5. NPV, Negative Predictive Value.
  6. ULSAM, Uppsala Longitudinal Study of Adult Men) cohort.
  7. *From ICD-7 through ICD-9, no distinction was made between type 1 and type 2 diabetes. For practical reasons "diabetes" has been listed as an autoimmune disorder.
  8. † These studies took place when the county in question did not yet report inpatient data to the IPR, but results are deemed valid for the IPR.