The validity of pathology codes for biopsy-confirmed kidney disease in the Danish National Patobank.

Background: This study validates the application of Systematized Nomenclature of Medicine second edition (SNOMED II) codes used to describe medical kidney biopsies in Denmark in encoded form, aiming to support robust epidemiological research on the causes, treatments and prognosis of kidney diseases. Methods: Kidney biopsy reports from 1 January 1998 to 31 December 2018 were randomly extracted from the Danish National Patobank, using SNOMED codes. A 5% sample was selected, and nephrologists assessed the corresponding medical records, assigning each case the applied clinical diagnoses. Sensitivity, specificity, positive predictive values (PPV), negative predictive values and Cohen's kappa coefficient for the retrieved SNOMED codes were calculated. Results: A total of 613 kidney biopsies were included. The primary clinical disease groups were glomerular disease (n = 368), tubulointerstitial disease (n = 67), renal vascular disease (n = 51), diabetic nephropathy (n = 51) and various renal disorders (n = 40). Several SNOMED codes were used to describe each clinical disease group and PPV for the combined SNOMED codes were high for glomerular disease (94%), diabetic nephropathy (85%) and systemic diseases affecting the kidney (96%). Conversely, tubulointerstitial disease (62%), renal vascular disease (60%) and other renal disorders (17%) showed lower PPV. Conclusions: SNOMED codes have a high PPV for glomerular diseases, diabetic nephropathy and systemic diseases affecting the kidney, in which they could be applied for future epidemiological research.

Trends in Lower Extremity Artery Disease Repair Incidence, Comorbidity, and Mortality: A Danish Nationwide Cohort Study, 1996-2018.

Background: The prevalence of occlusive lower extremity artery disease (LEAD) is rising worldwide while European epidemiology data are scarce. We report incidence and mortality of LEAD repair in Denmark from 1996 through 2018, stratified on open aorto-iliac, open peripheral, and endovascular repair. Methods: A nationwide cohort study of prospective data from population-based Danish registers covering 1996 to 2018. Comorbidity was assessed by Charlson's Comorbidity Index (CCI). Incidence rate (IR) ratios and mortality rate ratios (MRR) were estimated by multivariable Poisson and Cox regression, respectively. Results: We identified 41,438 unique patients undergoing 46,236 incident first-time LEAD repairs by either aorto-iliac- (n=5213), peripheral surgery (n=18,665) or percutaneous transluminal angioplasty (PTA, n=22,358). From 1996 to 2018, the age- and sex-standardized IR for primary revascularization declined from 71.8 to 50.2 per 100,000 person-years (IRR, 0.70; 95% CI, 0.66-0.75). Following a 2.5-fold IR increase of PTA from 1996 to 2010, all three repair techniques showed a declining trend after 2010. The declining IR was driven by decreasing LEAD repair due to claudication, and by persons aged below 80 years, while the IR increased in persons aged above 80 years (p interaction<0.001). LEAD repair was more frequent in men (IRRfemale vs male, 0.78; 95% CI, 0.77-0.80), which was consistent over calendar time (p interaction=0.41). Crude mortality decreased following open/surgical repair, and increased following PTA, but all three techniques trended towards lower adjusted mortality comparing the start and the end of the study period (MRRaorto-iliac, 0.71; 95% CI, 0.54-0.93 vs MRRperipheral, 0.76; 95% CI, 0.69-0.83 vs MRRPTA, 0.96; 95% CI, 0.86-1.07). Increasing age and CCI, male sex, smoking, and care dependency associated with increased mortality. Conclusion: The incidence rate of LEAD repair decreased in Denmark from 1996 to 2018, especially in persons younger than 80 years, and primarily due to reduced revascularization for claudication. Adjusted mortality rates decreased following open surgery, but seemed unaltered following PTA.

Trends in Abdominal Aortic Aneurysm Repair Incidence, Comorbidity, Treatment, and Mortality: A Danish Nationwide Cohort Study, 1996-2018.

Background: Significant changes in Western populations' abdominal aortic aneurysm (AAA) epidemiology have been reported following the introduction of screening, endovascular AAA repair, and reduced tobacco consumption. We report incidence and mortality of AAA repair in Denmark from 1996 to 2018, where AAA screening was not implemented. Methods: Nationwide cohort study of prospective data from population-based Danish registries covering 1996 to 2018. We identified 15,395 patients undergoing first-time AAA repair using the Danish Vascular Registry. Comorbidity was assessed by Charlson's Comorbidity Index (CCI). Incidence rate (IR) ratios and mortality rate ratios (MRR) were estimated by multivariable Poisson and Cox regression, respectively. Results: Overall AAA repair IR decreased by 24% from 1996 through 2018, mainly reflecting a 53% IR reduction in ruptured AAA repairs in men. Overall, the IR decreased 52-63% in age groups below 70 years and increased 81% among octogenarians. The proportion of intact AAAs repaired endovascularly increased from 2% in 1996-1999 to 42% in 2015-2018. For both ruptured and intact AAAs the CCI score increased by 0.9% annually independently of age and sex. The adjusted five-year MRR in 2016-2018 vs.1996-2000 was 0.46 (95% confidence interval (CI): 0.39-0.54) following ruptured and 0.51 (95% CI: 0.44-0.59) following intact AAA repair. Conclusion: In Denmark, overall AAA repair incidence decreased between 1996 and 2018, primarily reflecting a reduction among males and a shift to an older population requiring intervention. These trends mirror changes in tobacco consumption in Denmark. Regardless of age and comorbidity, AAA repair mortality decreased markedly during the study period.

The diagnosis of cerebral palsy in two Danish national registries: a validation study.

AIMS: To determine the quality of prospectively collected data from the highly specialized Danish Cerebral Palsy Follow-up Program (CPOP), and to establish the validity of a reported cerebral palsy (CP) diagnosis in the Danish National Patient Registry (NPR), regularly used as a proxy for neurodevelopmental disorders in epidemiological research. METHODS: We compared data from the two registries on children with registered CP, born in Denmark between 2008 and 2009, with information from medical records verified by two experienced physicians specializing in pediatric neurology. Data accuracy was estimated by completeness, correctness, and reliability. Completeness was calculated as the number of cases with correctly registered CP diagnoses divided by the total number of true CP diagnoses (similar to sensitivity). Correctness was calculated as the number of cases with correct registrations divided by the total number of cases (similar to positive predictive value). Reliability was estimated using kappa statistics. RESULTS: Registered CP diagnoses in the CPOP had high accuracy, with 94% correctness and 91% completeness. Furthermore, most key variables in the CPOP showed excellent reliability, especially variables defining the severity of the condition. In the Danish NPR, only 225 of 348 children with a noted CP diagnosis fulfilled the diagnostic criteria for CP, resulting in 65% correctness. CONCLUSIONS: Danish CPOP data are a valid source for epidemiological research. Conversely, a noted CP diagnosis in the Danish NPR was, at best, correct in only two out of three patients.

Burden of Chronic Obstructive Pulmonary Disease Attributable to Tuberculosis: A Microsimulation Study.

Tuberculosis (TB) is a risk factor for chronic obstructive pulmonary disease (COPD), but COPD is also a predictor of TB. The excess life-years lost to COPD caused by TB can potentially be saved by screening for and treating TB infection. We examined the number of life-years that could be saved by preventing TB and TB-attributable COPD. We compared the observed (no intervention) and counterfactual microsimulation models constructed from observed rates in the Danish National Patient Registry (covering all Danish hospitals between 1995 and 2014). In the Danish population of TB and COPD-naive individuals (n = 5,206,922), 27,783 persons (0.5%) developed TB. Among those who developed TB, 14,438 (52.0%) developed TB with COPD. Preventing TB saved 186,469 life-years overall. The excess number of life-years lost to TB alone was 7.07 years per person, and the additional number of life-years lost among persons who developed COPD after TB was 4.86 years per person. The life-years lost to TB-associated COPD are substantial, even in regions where TB can be expected to be identified and treated promptly. Prevention of TB could prevent a substantial amount of COPD-related morbidity; the benefit of screening and treatment for TB infection is underestimated by considering morbidity from TB alone.

Neonatal Phototherapy and Clinical Characteristics: The Danish National Patient Registry 2000-2016.

Purpose: Phototherapy is the standard treatment for neonatal hyperbilirubinemia. It is important to collect data on phototherapy to support research related to the efficacy and safety of phototherapy. We explored the registration of phototherapy in the Danish National Patient Registry (DNPR) and the clinical characteristics of neonates treated with phototherapy. Methods: We identified children born alive in Denmark from 1 January 2000 through 30 November 2016 from the DNPR (N=1,044,502). We calculated the proportion of children registered that received phototherapy during the neonatal period and examined temporal trends, both nationwide and at the level of individual hospitals. In a sub-cohort of children born at Aarhus University Hospital (AUH) in 2002-2016 (N=71,781), we analyzed the proportions of children registered that received phototherapy, according to sex, gestational age, birth weight, and neonatal characteristics, like Apgar score, birth asphyxia, and infections. Results: We identified 11,295 (1.1%) registered that received phototherapy. The proportions of children registered that received phototherapy differed among hospitals (range: 0 to 4.1%). Nationwide registration was low during the study period, but it increased to 1.8% in 2016. For the AUH sub-cohort the proportion of children registered with phototherapy averaged 4.4% (N=3182, range:3.9-5.1%). The proportion of children registered with phototherapy was inversely correlated with gestational age and birth weight, and positively correlated with neonatal characteristics, including low Apgar score, birth asphyxia, and infections. Conclusion: Phototherapy was under-reported in the DNPR and the proportions of children registered that received phototherapy differed among hospitals. The non-compulsory policy for reporting treatment and care in hospitals to the DNPR might explain the variation. The most consistent reporting was observed among children born in an university hospital, where 4.4% of children registered that received phototherapy, and phototherapy was inversely associated with gestational age, birth weight, and positively associated with clinical characteristics like birth asphyxia, and infections.

Validity of Algorithm for Classification of In- and Outpatient Hospital Contacts in the Danish National Patient Registry.

Purpose: Following the implementation of the 3rd version of the Danish National Patient Register (DNPR-3), information on whether hospitalizations were inpatient, outpatient, or emergency room (ER) contacts was no longer readily available. This study examined the positive predictive values (PPV) of a common algorithm to characterize hospitalizations as inpatient, outpatient, or emergency room (ER) contacts in both DNPR-2 and DNPR-3. Patients and Methods: All hospital contacts in North Denmark Region were identified in the DNPR within a 1-year window of the implementation of DNPR-3 in early 2019. An algorithm based upon proportion of overnight (±50%) and elective (±50%) contacts for each hospital department was developed. Next, PPVs of these categorizations were computed using manual characterization of all departments and clinics by two experienced clinicians as reference. Second, the reliability of various time intervals to join department contacts and subsequent categorization of overnight hospital stays as proxies for inpatient contacts was explored. Results: The algorithm yielded PPVs of 91% and 89% for hospital units and related contacts categorized as inpatient in DNPR-2 and 100% for both parameters in DNPR-3. In outpatient units, the PPVs were 99% in both DNPR-2 and DNPR-3, whereas the corresponding PPVs were 99.6% and 99% on the contact level. In contrast, the PPV for ERs was 33% in DNPR-2 and 56% in DNPR-3, primarily due to misclassification of outpatient clinics. Still, the proportion of correctly categorized ER contacts was 87% in DNPR-2 and 85% in DNPR-3. Using time intervals from 0 to 12 hours to join department contacts showed that overnight hospitalizations comprised inpatient contacts in 97% in DNPR-2 and 98% in DNPR-3. However, the sensitivity was moderate at 76-78% for all inpatient hospitalizations in DNPR-2 and DNPR-3. Conclusion: This algorithm accurately categorized hospitalizations as inpatient, outpatient, or ER contacts in both DNPR-2 and DNPR-3.

Positive Predictive Values of Procedure Codes on the Treatment of Non-Muscle Invasive Bladder Cancer in the Danish National Patient Registry.

Purpose: Globally non-muscle invasive bladder cancer (NMIBC) is a high-incidence disease. There is a large heterogeneity within NMIBC regarding recurrence- and progression risks, and large-scale studies of treatment patterns and prognoses in an everyday setting could result in NMIBC-subgroup treatment optimization, benefiting both patients and the economy. The Danish national registries provide such an opportunity if the registered procedure codes are valid. Therefore, the aim of the study was to validate the International Classification of Diseases, 10th Edition (ICD-10) codes of NMIBC treatment used in the Danish National Patient Registry (DNPR). Patients and Methods: From the DNPR, we randomly selected 200 NMIBC treatment courses identified by the dates of the course and the codes of transurethral resection of the bladder ((TURB), n = 125), photodynamic diagnosis ((PDD), n = 25), bladder instillation with Bacillus Calmette vaccine ((BCG), n = 25), or bladder instillation with chemotherapy/Mitomycin C ((MMC), n = 25). We used medical record reviews as the reference standard and estimated positive predictive values (PPVs) of all procedure codes and negative predictive values (NPVs) of PDD- and the perioperative single-shot MMC codes. Results: We identified the medical records in 150 (75%) of the 200 treatment courses (149 individual patients). The overall PPVs were TURB: 98.9% (95% confidence interval: 93.8; 100.0%), PDD: 95.8% (78.9; 99.9%), adjuvant BCG: 90.0% (68.3; 98.8%), perioperative single-shot MMC 1/5, and adjuvant MMC: 69.2% (38.6; 90.9%). The overall NPVs were PDD: 64.8% (54.4; 73.9%) and perioperative single-shot MMC: 97.7% (92.1; 99.4%). Conclusion: The ICD-10 NMIBC procedure codes recorded in the DNPR are generally valid with high PPVs. The NPV of the PPD code is acceptable. However, the code for perioperative single-shot MMC is uncertain with low PPV, but a high NPV.

Validity of Inflammatory Bowel Disease Diagnoses in the Danish National Patient Registry: A Population-Based Study from the North Denmark Region.

Purpose: The Danish National Patient Registry (DNPR) is recognized for providing high-quality data. However, only a few minor studies have validated inflammatory bowel disease (IBD) diagnoses in the DNPR, reporting various degrees of validity. To pave the way for large-scale studies of IBD in Denmark, we aimed to investigate the validity of IBD among >8000 patients registered in the DNPR between 2002 and 2020 in the North Denmark Region. Patients and Methods: To evaluate the reliability of the diagnoses in the DNPR, we initially compared all patients registered with one IBD diagnosis during 2002-2020 to a list of already verified patients in the regional IBD database GASTROBIO. Medical records on all DNPR registered patients not on the list were manually reviewed by a gastroenterologist to verify or dismiss the IBD diagnosis. Positive predictive values (PPV) were calculated. Results: Of 8040 patients with at least one IBD diagnosis in DNPR, 5263 were already confirmed cases, leaving 2777 for medical record evaluation, of whom 849 had IBD. In total, 6112 were correctly registered with IBD based on one diagnosis, and 1343 were incorrectly registered, resulting in a PPV of 0.82 (95% CI, 0.81-0.83). For patients registered with at least two diagnoses, the PPV was 0.95 (95% CI, 0.95-0.96), and with at least three diagnoses, the PPV was 0.98 (95% CI, 0.98-0.99). Results were similar for UC and CD separately. Of note, the completeness of valid cases went from 6112 to 4606 (75%; 95% CI, 74%-76%) when demanding at least two registered diagnoses and to 3320 (54%; 95% CI, 53%-56%) when demanding at least three registered diagnoses. Conclusion: Reassuringly, the validity of IBD diagnoses in DNPR is high, especially for patients registered more than once. However, the reduced completeness when applying a true case definition of at least two registered diagnoses should be considered.

Importance of Reporting Complete Procedures of Identifying Patients from the Danish National Patient Registry: The Case of Neonatal Jaundice and Epilepsy.

Objective: The Danish National Patient Registry (DNPR) is a valuable resource for medical and epidemiological Research. However, not all research articles fully described procedures they used to identify events. In this study, we compared two approaches in identifying persons with a disease diagnosis using neonatal jaundice and epilepsy as examples. Methods: A cohort of singletons born alive between the 1st January 1997 and the 30th November 2016 in Denmark was used for this purpose. Diagnostic information for a hospital contact in the registry included a primary diagnosis, secondary diagnoses, referral diagnoses, and additional information to a diagnosis (associated diagnoses), if any. Approach 1 identified patients of interest by considering all diagnostic information with exclusion of referral diagnoses only. Approach 2 identified patients of interest by additionally excluding diagnoses from a hospital contact that were coded with Z00 - Z99 of ICD-10 (for health service on examination and reproduction, etc.) as the main reason of the hospital contact. We presented the proportion of people with a diagnosis of neonatal jaundice and epilepsy by the two approaches and explored the potential explanations for the difference. Results: For the example of neonatal jaundice, the study population included N=1,186,683 persons. The proportion of children with a diagnosis of neonatal jaundice was 5.5% (n=66,736) by approach 1 and 3.9% (n=45,928) by approach 2. For the example of epilepsy, the study population included N=1,183,273 persons. The proportion of children with a diagnosis of epilepsy were 1.2% (n=14,604) by approach 1 and 0.9% (n=10,441) by approach 2. Discussion: This study demonstrated that the two approaches identified different proportion of persons with a diagnosis of neonatal jaundice and epilepsy. We advocated researchers report complete procedures of identifying patients for making research findings reproducible and comparable.

High Validity of the Danish National Patient Registry for Systemic Anticancer Treatment Registration from 2009 to 2019.

BACKGROUND: The Danish National Patient Registry is a major resource for Danish epidemiology. Only a few studies have been conducted to check the validity of the reporting of systemic anticancer treatments. In this study, we assessed this validity for a range of cancer types over a long period of time. PATIENTS AND METHODS: We extracted systemic anticancer treatment procedures from the Danish National Patient Registry for patients with solid malignant tumors treated at the Department of Oncology at Aalborg University Hospital between 2009 and 2019 (12,014 patients with 215,293 drug records). These data were compared to records obtained from the antineoplastic prescription database used at the department. We estimated the sensitivity, positive predictive value (PPV), and F1-score defined as the harmonic mean of the sensitivity and the PPV. RESULTS: There was an overall high concordance between the two datasets with a sensitivity and a PPV >92%. Treatments for brain, ovarian and endometrial cancers displayed lower concordance (81-89%). The validity was stable over the study period, with a slight drop during 2016-2017. Most drugs had a high validity with F1-scores above 90%. Fluorouracil, gemcitabine, pemetrexed, pembrolizumab, and nivolumab had F1-scores above 97%. Drugs that were introduced in the study period, such as lapatinib, palbociclib, erlotinib, pertuzumab, and panitumumab, yielded lower F1-scores due to the absence of specific registry codes early after introduction. CONCLUSION: The Danish National Patient Registry can be used to reliably obtain information about systemic anticancer treatments, keeping in mind limitations for recently introduced drugs and for some types of cancer.

Positive Predictive Value of Diagnostic Codes for Inflammatory Bowel Disease in the Danish National Patient Registry Among Individuals 50+ Years, Using Patient Records as Reference Standard.

PURPOSE: Inflammatory bowel diseases (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), are chronic diseases. The aim was to validate diagnoses of IBD among patients aged 50+ years in the Danish National Patient Registry (NPR) by comparison with patient medical records. PATIENTS AND METHODS: Men and women in the Diet, Cancer and Health (DCH) cohort were linked to NPR, and cases with a diagnosis of IBD and their respective hospital records were identified. Validation was performed by comparing patient medical records with information on discharge diagnoses of IBD from the NPR. RESULTS: Of 57,053 individuals in the DCH-cohort, 339 were registered with an IBD diagnosis in NPR, with 277 (82%) records available for review. Among 277 patients, the positive predictive values (PPVs) of one CD or UC registration in NPR were 78% for IBD overall, 51% for CD and 54% for UC. One hundred fifty-seven patients had at least two CD and/or UC registrations with PPVs of 90% for IBD overall, 65% for CD and 73% for UC. One hundred and two patients had at least three registrations with PPVs of 97% for IBD overall, 75% for CD and 88% for UC. 96% were diagnosed at a specialized department. Other diagnoses coded as IBD mostly included microscopic colitis, irritable bowel syndrome and cancer. CONCLUSION: Validity of IBD diagnoses in the registry of individuals aged 50+ years increased with the number of registrations. It is recommended that these results are taken into consideration in future studies, especially in epidemiology research using NPR as a data source for patients diagnosed with IBD.

How "benign" is cutaneous mastocytosis? A Danish registry-based matched cohort study.

BACKGROUND: There are limited estimates of the incidence rates (IRs) of mastocytosis, and only a few studies have addressed the long-term consequences of living with these diagnoses. Previous reports have shown that systemic mastocytosis is associated with leukemic transformations and an increased risk of death as opposed to cutaneous mastocytosis (CM) and indolent systemic mastocytosis (ISM), which have benign diagnoses with life expectancy rates similar to those of the background population. OBJECTIVE: This study aimed to analyze the incidence and mortality of mastocytosis. METHODS: A population-based matched cohort study of patients with mastocytosis between 1 January 1, 1977 and 31 December 31, 2014 was identified from the Danish National Health Registries. IRs of CM, ISM, and pediatric mastocytosis were highlighted. Survival estimates were compared with those of a healthy background population, using a Cox proportional hazard model. RESULTS: A total of 1461 patients with mastocytosis were identified. The annual IR of overall mastocytosis was 1.1 per 100,000 person years (95% confidence interval [CI], 1.0-1.2). Among children, the IR was 1.8 per 100,000 person years (95% CI, 1.6-2.1). The prevalence of any comorbidity was twice as high among patients with mastocytosis compared with the population without mastocytosis (odds ratio: 2.1; 95% CI, 1.8-2.5). The Charlson Comorbidity Index-adjusted mortality among adult patients with mastocytosis was HRCutaneous Mastocytosis 1.2 (95% CI, 0.8-1.9), HRIndolent Systemic Mastocytosis 1.9 (95% CI 1.4-2.5), and HRSystemic Mastocytosis 4.2 (95%, CI 1.9-9.4), respectively. CONCLUSION: Based on an entire nation, with free health care at the point of access, we estimated an annual IR of mastocytosis and its subgroups. We discovered that patients with ISM had an increased risk of death compared with the general population. Our data supported the overall benign nature of CM diagnosed after age 2 years.

Positive Predictive Value of the Giant Cell Arteritis Diagnosis in the Danish National Patient Registry: A Validation Study.

PURPOSE: To investigate the positive predictive value (PPV) of the giant cell arteritis (GCA) diagnosis in the Danish National Patient Registry (DNPR). PATIENTS AND METHODS: A total of 293 patients aged ≥50 years with a first-time diagnosis of GCA in the DNPR between January 2012 and December 2017 were included. Patients were sampled from two secondary and one tertiary care hospitals in the Central Region Denmark. Two independent investigators (PH & PT) reviewed all medical files, including medical records, treatment, biochemistry, histopathology and imaging, and either confirmed or dismissed the diagnosis of GCA. In case of disagreement, a consensus agreement was reached. Sub-analyses including number of redeemed prescriptions performed temporal artery biopsies (TABs), and number of GCA-related hospital contacts were performed. RESULTS: We confirmed the diagnosis of GCA in 183/293 patients resulting in a PPV of 62% (95% CI: 57-68). In patients with ≥3 redeemed prescriptions of glucocorticoids (GCs), we confirmed the diagnosis in 166/214 resulting in a PPV of 78% (95% CI: 71-83). In patients with ≥3 redeemed prescriptions of GCs and ≥3 GCA-related hospital contacts, we confirmed the diagnosis in 88/95 resulting in a PPV of 93% (95% CI: 85-96); however, this only included 88/183 confirmed GCA patients. CONCLUSION: This is the first study to validate the diagnostic code of GCA in the DNPR. The overall PPV of GCA in the DNPR was 62%. Requiring redeemed prescriptions of GCs and/or GCA-related hospital contacts increase the PPV, but also excludes a significant number of GCA patients.

Validation of ulcerative colitis and Crohn's disease and their phenotypes in the Danish National Patient Registry using a population-based cohort.

INTRODUCTION: The Danish National Patient Registry (DNPR) has been the source of several epidemiological studies of inflammatory bowel disease (IBD). However, the validation dates back to 1996 and lacks outpatient records and disease classification. The aim of this study was to update the validation and assess the validity and reliability of using the registry in disease classification. METHODS: Validation of the registry was done using a population-based inception cohort of IBD patients from 2003 to 2011 consisting of 513 patients. Specificity and sensitivity were calculated for the diagnoses of Crohn's disease (CD) and ulcerative colitis (UC), age at diagnosis and disease classification according to the Montreal Classification at both time of diagnosis and end of follow-up. RESULTS: The registry showed high validity and reliability in identifying CD and UC patients concerning correct age classification and identifying perianal disease. The registry showed inconsistent, unreliable results in further disease classification. CONCLUSIONS: The DNPR has good validity and reliability in identifying patients with CD and UC, and defining the age of patients at diagnosis. However, categorising IBD patients according to the Montreal Classification should not be carried out using DNPR data in their current form, except when identifying CD patients with perianal disease.

Risk of comorbidities in patients diagnosed with chronic urticaria: A nationwide registry-study.

BACKGROUND: The autoimmune profile of Chronic Urticaria (CU) patients is an increasing topic of interest. Associated diseases suggest shared pathogenic pathways, and they may provide important knowledge on specific targets for future treatment models. In this study we examined the prevalence and risk of comorbidities in CU. METHODS: The Danish National Patient Registry was used to identify all CU patients from 1994 to 2015. Five of 5 specialized dermatological units in Denmark were covered. Analyses were conducted as a nested case control study and a matched cohort study. CSU patients were matched 1:10 on age and sex to an otherwise random group of people from the background population. RESULTS: A total of 12,185 CU patients were identified, with an overweight of female cases (69% versus 32%). There was an overrepresentation of mast cell mediated diseases including mastocytosis and anaphylaxis, as well as atopic diseases including type 1 allergies and atopic dermatitis. The prevalence of rheumatoid arthritis, systemic lupus erythematosus, thyroiditis and vitiligo was also increased, as was the prevalence of depression. CU patients who did not have any of the co-morbidities at the time of their CU diagnosis had an increased risk of developing both mast cell mediated diseases, atopic diseases, and autoimmune diseases excluding thyroiditis and diabetes. CONCLUSION: The autoimmune profile of the comorbidities of CU was demonstrated with an evident risk of developing rheumatoid arthritis. CU patients were also at increased risk of either having or achieving depression. Mast cell related diseases seemed to be overrepresented, although registry data within this disease category are questionable and similar to symptoms of CU to the untrained eye. Thus, CU patients constitute a multimorbid group of patients, which must be recognized among treating physicians.

Positive predictive value of acute and chronic pancreatitis diagnoses in the Danish National Patient Registry: A validation study.

Aims: To examine the validity of the diagnoses of acute and chronic pancreatitis registered in the Danish National Patient Registry. Methods: We identified all patients in the Danish National Patient Registry admitted to two Danish hospitals with acute or chronic pancreatitis from 1996 to 2013. From this population, we randomly sampled 100 patients with acute pancreatitis and 100 patients with chronic pancreatitis. For each cohort, we computed the positive predictive values and associated 95% confidence intervals (CIs) for the discharge diagnosis of acute or chronic pancreatitis using medical records as the gold standard. Results: We identified 2617 patients with acute pancreatitis and 1284 patients with chronic pancreatitis discharged from either of the two hospitals during the study period. Of these, 776 (19.9%) had a diagnosis of both acute and chronic pancreatitis and are thus present in both cohorts. From the 200 sampled patients, a total of 138 (69.0%) medical records were available for review. The positive predictive value for a diagnosis of acute pancreatitis in the Danish National Patient Registry was 97.3% (95% CI 90.5-99.2%) and for chronic pancreatitis 83.1% (95% CI 72.2-90.3%). Conclusions: The validity of diagnoses of acute and chronic pancreatitis registered in the Danish National Patient Registry since 1996 is generally high.

Positive predictive value of infective endocarditis in the Danish National Patient Registry: a validation study.

The positive predictive value of an infective endocarditis diagnosis is approximately 80% in the Danish National Patient Registry. However, since infective endocarditis is a heterogeneous disease implying long-term intravenous treatment, we hypothesiszed that the positive predictive value varies by length of hospital stay. A total of 100 patients with first-time infective endocarditis in the Danish National Patient Registry were identified from January 2010 - December 2012 at the University hospital of Aarhus and regional hospitals of Herning and Randers. Medical records were reviewed. We calculated the positive predictive value according to admission length, and separately for patients with a cardiac implantable electronic device and a prosthetic heart valve using the Wilson score method. Among the 92 medical records available for review, the majority of the patients had admission length ⩾2 weeks. The positive predictive value increased with length of admission. In patients with admission length <2 weeks the positive predictive value was 65% while it was 90% for admission length ⩾2 weeks. The positive predictive value was 81% for patients with a cardiac implantable electronic device and 87% for patients with a prosthetic valve. The positive predictive value of the infective endocarditis diagnosis in the Danish National Patient Registry is high for patients with admission length ⩾2 weeks. Using this algorithm, the Danish National Patient Registry provides a valid source for identifying infective endocarditis for research.

Positive predictive value of peptic ulcer diagnosis codes in the Danish National Patient Registry.

BACKGROUND: Diagnoses of peptic ulcer are registered in the Danish National Patient Registry (DNPR) for administrative as well as research purposes, but it is unknown whether the coding validity depends on the location of the ulcer. OBJECTIVE: To validate the International Classification of Diseases, 10th revision diagnosis codes of peptic ulcer in the DNPR by estimating positive predictive values (PPVs) for gastric and duodenal ulcer diagnoses. METHODS: We identified all patients registered with a hospital discharge diagnosis of peptic ulcer from Aarhus University Hospital, Denmark, in 1995-2006. Among them, we randomly selected 200 who had an outpatient gastroscopy at the time of ulcer diagnosis. We reviewed the findings from these gastroscopies to confirm the presence of peptic ulcer and its location. We calculated PPVs and corresponding 95% confidence intervals (CIs) of gastric and duodenal ulcer diagnoses, using descriptions from the gastroscopic examinations as standard reference. RESULTS: In total, 182 records (91%) were available for review. The overall PPV of peptic ulcer diagnoses in DNPR was 95.6% (95% CI 91.5-98.1), with PPVs of 90.3% (95% CI 82.4-95.5) for gastric ulcer diagnoses, and 94.4% (95% CI 87.4-98.2) for duodenal ulcer diagnoses. PPVs were constant over time. CONCLUSION: The PPV of uncomplicated peptic ulcer diagnoses in the DNPR is high, and the location of the ulcers is registered correctly in most cases, indicating that the diagnoses are useful for research purposes.

The completeness of chest X-ray procedure codes in the Danish National Patient Registry.

OBJECTIVE: The aim of this validation study was to assess the completeness of the registrations of chest X-rays (CXR) in two different versions of the Danish National Patient Registry (DNPR). MATERIAL AND METHODS: We included electronic record data on CXR performed on patients aged 40 to 99 years from nine radiology departments covering 20 Danish hospitals. From each department, we included data from three randomly selected weeks between 2004 and 2011 (reference standard). In two versions of the DNPR from the State Serum Institute (SSI) and Statistics Denmark, respectively, we investigated the proportion of registered CXR compared to the reference standard. Furthermore, we compared the completeness of the recorded data according to the responsible department (main department). RESULTS: We identified 11,235 patients and 12,513 CXR in the reference standard. The data from the SSI contained 12,265 (98%) CXR, whereas the data from Statistics Denmark comprised 9,151 (73.1%) CXR. The completeness of the SSI data was fairly constant across years, radiology departments, medical specialties, and age groups. The data from Statistics Denmark was almost complete in 2011 (95.8%). However, for the remaining study period, the data with radiology departments registered as the main department were lacking in the version from Statistics Denmark, and so the overall completeness was 73.1%. CONCLUSION: The completeness of CXR registrations varied between 98% and 73% depending on the information source, and this should be considered when investigating radiology services in the basis of DNPR.