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Background: Observational epidemiologic studies often yield different results on the same question. In this article, we explain how this comes about., Methods: In this review, which is based on publications retrieved by a selective search in PubMed and the Web of Science, we use information from international publications, simulation studies on sampling error, and a quantitative bias analysis on fictitious data to demonstrate why the results of epidemiologic studies are often uncertain, and why it is, therefore, generally necessary to perform more than one study on any particular question., Results: Sampling errors, imprecise measurements, alternative but equally appropriate methods of data analysis, and features of the populations being studied are common reasons why studies on the same question can yield different results. Simulation studies are used to illustrate the fact that effect estimates such as relative risks or odds ratios can deviate markedly from the true value because of sampling error, i.e., by chance alone. Quantitative bias analysis is used to show how strongly effect estimates can be distorted by misclassification of exposures or outcomes. Finally, it is shown through illustrative examples that different but equally appropriate methods of data analysis can lead to divergent study results., Conclusion: The above reasons why epidemiologic study results can be heterogeneous are explained in this review. Quantitative bias analyses and sensitivity analyses with alternative data evaluation strategies can help explain divergent results on one and the same question.

Background: Deviations in serum creatinine (SCr), due to its determination using a Jaffe or an enzymatic method, have an effect on kidney disease detection and staging. It is not yet clear how large this effect is in kidney transplant recipients (KTRs). SCr measurement differences are of particular importance here to evaluate the graft function. Methods: The results of all parallel SCr measurements (Jaffe and enzymatic method) of adult outpatient KTRs in the same serum sample at the University Hospital Essen (Germany) between January 2020 and October 2023 were evaluated. A Bland-Altman plot with 95% limits of agreement (LoA) was used to assess the difference between the Jaffe and the enzymatic SCr (eSCr). For all patients, we used the CKD-EPI 2009 and EKFC formula, and for patients ≥ 70 years, we also used the BIS1 formula for the determination of eGFR. Results: A total of 12,081 parallel SCr measurements from 1243 KTRs were analyzed, where 61% were male and the median age was 53 years. On average, Jaffe SCr was 0.03 mg/dL higher than eSCr (LoA -0.16; 0.21 mg/dL). On average, the eGFR determined by Jaffe SCr was 1.9 mL/min/1.73 m 2 lower than the eGFR determined by eSCr (LoA -9.5; 5.7 mL/min/1.73 m 2 ). The comparison of eGFR between the two SCr methods revealed a different CKD stage in 1589 (13%) of all analyzed measurements, most frequently between G2/G3a (41%) and G3a/G3b (24%). When using the EKFC and BIS1 formulas, there were approximately the same number of measurements leading to a different CKD stage. Conclusions: In more than every tenth SCr determination in outpatient KTRs, the difference between the Jaffe and enzymatic methods had an influence on the assignment to a CKD stage. This effect was comparably pronounced for all eGFR formulas applied.

Background: Albumin, as the most abundant plasma protein, represents a target structure for both drug and physicochemical therapeutic approaches to eliminate uraemic toxins more efficiently. Potentially, this approach could reduce mortality of haemodialysis patients. However, little is known about albumin functional properties in these patients and its alteration by haemodialysis treatment., Methods: The binding and detoxification efficiency of albumin were assessed by electron paramagnetic resonance spectroscopy using a spin-labelled fatty acid. Binding efficiency (BE) reflects strength and amount of bound fatty acids under certain ethanol concentration. Detoxification efficiency (DTE) reflects the molecular flexibility of the patient's albumin molecule, thus the ability to change the conformation depending on ethanol concentration. Percentage of BE and DTE are depicted in relation to healthy individuals (100%)., Results: Fifty-eight patients (59% male, median age 68 years, median time on haemodialysis 32 months) were included in the study. Before haemodialysis treatment, albumin binding and detoxification efficiency were substantially below healthy individuals [median BE 52% (interquartile range, IQR, 45%-59%); median DTE 38% (IQR 32-49%)]. After haemodialysis treatment, median BE and DTE significantly decreased [BE 28% (IQR 20-41%); DTE 11% (IQR 7%-27%; P < .001)]. BE and DTE decline after haemodialysis was not dependent on age, sex or treatment modalities, but was to a certain extent on the level of non-esterified fatty acids., Conclusion: Albumin binding and detoxification efficiency of fatty acids in maintenance haemodialysis patients were substantially below those in healthy individuals and even declined after dialysis treatment. These findings might be helpful when considering new therapeutic approaches in maintenance haemodialysis patients., (© The Author(s) 2023. Published by Oxford University Press on behalf of the ERA.)

Background: The validity of self-reported chronic conditions has been assessed by comparing them with medical records or register data in several studies. However, the reliability of self-reports of chronic diseases has less often been examined. Our aim was to assess the proportion and determinants of inconsistent self-reports of diabetes in a long panel study., Methods: SHARE (Survey of Health, Ageing and Retirement in Europe) includes 140,000 persons aged ≥ 50 years from 28 European countries and Israel. We used data from waves 1 to 7 (except wave 3) collected between 2004 and 2017. Diabetes was assessed by self-report. An inconsistent report for diabetes was defined as reporting the condition in one wave, but denying it in at least one later wave. The analysis data set included 13,179 persons who reported diabetes, and answered the question about diabetes in at least one later wave. Log-binomial regression models were fitted to estimate crude and adjusted relative risks (RR) with 95% confidence intervals (CI) for the associations between various exposure variables and inconsistent report of diabetes., Results: The proportion of persons with inconsistent self-reports of diabetes was 33.0% (95% CI: 32.2%-33.8%). Inconsistencies occurred less often in persons taking antidiabetic drugs (RR = 0.53 (0.53-0.56)), persons with BMI ≥ 35 kg/m 2 versus BMI < 25 kg/m 2 (RR = 0.70, (0.64-0.77)), and poor versus excellent subjective health (RR = 0.87 (0.75-1.01)). Inconsistencies occurred more often in older persons (RR = 1.15 (1.12-1.18) per 10 years increase of age), and persons not reporting their age at diabetes onset (RR = 1.38 (1.31-1.45))., Conclusion: In SHARE, inconsistent self-report of diabetes is frequent. Consistent reports are more likely for persons whose characteristics make diabetes more salient, like intake of antidiabetic medication, obesity, and poor subjective health. However, lack of attention in answering the questions, and poor wording of the items may also play a role., (© 2024. The Author(s).)

Background: In former studies, parity was associated with adverse cardiovascular outcomes in parents. This study aims to extend the limited existing data regarding the association between the number of children and heart disease and/or stroke in a large longitudinal study in different European countries in both men and women., Methods: For 42 075 subjects (18 080 men, 23 995 women; median age 58 years (interquartile range: 53 to 65)) from 19 European countries and Israel in the Survey of Health, Ageing and Retirement in Europe (SHARE), odds ratios (OR) for the association between number of children and incident self-reported heart disease and/or stroke (HDS) were estimated using logistic regression analyses. Persons with one or two children were used as reference. The final model was adjusted for baseline age, sex, education, region, and marital status. All analyses were stratified by sex., Results: Women with seven or more children had the highest OR for the association between the number of children and incident HDS (OR = 2.12 [95% CI: 1.51 to 2.98]), while men with six children showed the highest OR (OR = 1.62 [1.13 to 2.33]). Stratified by education, across all education levels, men and women with five or more children had the highest ORs for this association. The highest OR was observed in both women and men in the group with primary education (OR = 1.66 [1.29 to 2.15] and OR = 1.60 [1.19 to 2.14], respectively). Stratified by region, both men and women with five or more children showed the highest ORs in Southern Europe (OR = 2.07 [1.52 to 2.82] and OR = 1.75 [1.25 to 2.44], respectively)., Conclusion: In this long-term follow-up study in various countries in Europe and Israel we found a positive association between number of children and incident HDS. This association was more pronounced in lower educated subjects and showed regional variations., (© 2023. The Author(s).)

Background: Hospital mortality after acute myocardial infarction (AMI, ICD-10: I21-I22) is used as OECD indicator of the quality of acute care. The reported AMI hospital mortality in Germany is more than twice as high as in the Netherlands or Scandinavia. Yet, in Europe, Germany ranks high in health spending and availability of cardiac procedures. We provide insights into this contradictory situation., Methods: Information was collected on possible factors causing the reported differences in AMI mortality such as prevalence of risk factors or comorbidities, guideline conform treatment, patient registration, and health system structures of European countries. International experts were interviewed. Data on OECD indicators 'AMI 30-day mortality using unlinked data' and 'average length of stay after AMI' were used to describe the association between these variables graphically and by linear regression., Results: Differences in prevalence of risk factors or comorbidities or in guideline conform acute care account only to a smaller extent for the reported differences in AMI hospital mortality. It is influenced mainly by patient registration rules and organization of health care. Non-reporting of day cases as patients and centralization of AMI care-with more frequent inter-hospital patient transfers-artificially lead to lower calculated hospital mortality. Frequency of patient transfers and national reimbursement policies affect the average length of stay in hospital which is strongly associated with AMI hospital mortality (adj R 2  = 0.56). AMI mortality reported from registries is distorted by different underlying populations., Conclusion: Most of the variation in AMI hospital mortality is explained by differences in patient registration and organization of care instead of differences in quality of care, which hinders cross-country comparisons of AMI mortality. Europe-wide sentinel regions with comparable registries are necessary to compare (acute) care after myocardial infarction., (© 2023. The Author(s).)

Background: Serum creatinine (SCr), mainly determined by the Jaffe or an enzymatic method, is the central marker to assess kidney function. Deviations between these two methods may affect the diagnosis and staging of acute kidney injury (AKI) and chronic kidney disease (CKD)., Methods: The results of the first parallel SCr measurement (Jaffe and enzymatic method) of adult in- and outpatients in the same serum sample at the University Hospital Essen (Essen, Germany) between 2020-2022 were retrospectively evaluated. A Bland-Altman plot with 95% limits of agreement (LoAs) was used to assess the difference between the Jaffe and the enzymatic SCr (eSCr) method. We used the 2009 Chronic Kidney Disease Epidemiology Collaboration equation for determination of estimated glomerular filtration rate (eGFR) according to the Kidney Disease: Improving Global Outcomes guidelines., Results: A total of 41 144 parallel SCr measurements were evaluated. On average, Jaffe SCr was 0.07 mg/dl higher than eSCr (LoA -0.12; 0.25 mg/dl). In 19% of all cases there was a different CKD stage when comparing eGFR between both SCr methods, of which 98% resulted in a more severe CKD stage determined with Jaffe SCr. In 1.6% of all cases Jaffe SCr was ≥0.3 mg/dl higher than eSCr., Conclusion: The present study showed that methods of SCr measurement may affect both the diagnosis and staging of AKI and CKD. This must be taken into account when interpreting measurements of renal function in everyday clinical practice, but also when planning and comparing studies on renal diseases. One should therefore stay with one method for SCr measurement, preferably with the enzymatic method., Competing Interests: A.K. is a member of the CKJ editorial board and has received grants for clinical studies, speaker fees, honoraria and travel expenses from Actelion, Amgen, Amicus, Alexion, Astellas, Bayer, Baxter, Binding Site, Bristol-Myers Squibb, Chiesi, CytoSorbents, Fresenius, GlaxoSmithKline, Hexal, Janssen, Kyowa Kirin, MSD, Novartis, Otsuka, Peripal, Pfizer, Roche, Sanofi, Shire, Teva and Vifor Fresenius Medical. All other authors declare no conflicts of interests., (© The Author(s) 2023. Published by Oxford University Press on behalf of the ERA.)

Background: Since social distancing during the COVID-19-pandemic had a profound impact on professional life, this study investigated the effect of PCR testing on on-site work., Methods: PCR screening, antibody testing, and questionnaires offered to 4,890 working adults in Lower Saxony were accompanied by data collection on demographics, family status, comorbidities, social situation, health-related behavior, and the number of work-related contacts. Relative risks (RR) with 95 % confidence intervals were estimated for the associations between regular PCR testing and other work and health-related variables, respectively, and working on-site. Analyses were stratified by the suitability of work tasks for mobile office., Results: Between April 2020 and February 2021, 1,643 employees underwent PCR testing. Whether mobile working was possible strongly influenced the work behavior. Persons whose work was suitable for mobile office (mobile workers) had a lower probability of working on-site than persons whose work was not suitable for mobile office (RR = 0.09 (95 % CI: 0.07 - 0.12)). In mobile workers, regular PCR-testing was slightly associated with working on-site (RR = 1.19 (0.66; 2.14)). In those whose working place was unsuitable for mobile office, the corresponding RR was 0.94 (0.80; 1.09). Compared to persons without chronic diseases, chronically ill persons worked less often on-site if their workplace was suitable for mobile office (RR = 0.73 (0.40; 1.33)), but even more often if their workplace was not suitable for mobile office (RR = 1.17 (1.04; 1.33))., Conclusion: If work was suitable for mobile office, regular PCR-testing did not have a strong effect on presence at the work site., Trial Registration: An ethics vote of the responsible medical association (Lower Saxony, Germany) retrospectively approved the evaluation of the collected subject data in a pseudonymized form in the context of medical studies (No. Bo/30/2020; Bo/31/2020; Bo/32/2020)., (© 2023. The Author(s).)

Introduction: Chronic kidney failure (CKD) is as common as diabetes or coronary heart disease in a population aged 40 years and older. Although CKD increases the risk of secondary diseases or premature death, patients with CKD are often unaware of their disease. In a recent analysis of German data, unawareness CKD was higher in women than in men., Methods: Baseline data from 2010 of 3,305 CKD patients from German cohort studies and registries were analyzed. Stage 1-4 CKD was defined by eGFR (estimated glomerular filtration rate) and albumin-creatinine ratio according to the KDIGO-guideline. Patient knowledge of CKD was coded according to self-report. The proportion of patients without knowledge of CKD and the sex-specific proportion difference (each with 95 % confidence interval) were calculated according to CKD stages and additional comorbidities (diabetes, hypertension, anemia, and cardiovascular disease). In addition, the prevalence ratio (PR) for not knowing about CKD was estimated for women compared to men crude and adjusted for age and other risk factors., Results: Women were less likely than men to know about their CKD in all subgroups studied by age, CKD stage, and comorbidities. The proportion difference for CKD awareness increased with higher CKD stage and was 21 percentage points (7.6; 34.6) at the expense of women in CKD stage 4. Among patients with CKD stage 3b and concomitant grade 2 hypertension, 61 % of women versus 45 % of men were unaware of their disease. The PR for CKD unawareness in women compared with men in the fully adjusted model increased from 1.08 (1.00; 1.16) in CKD stage 3a to 1.75 (1.14; 2.68) in CKD stage 4., Conclusion: Despite the presence risk factors that necessitate monitoring of renal function, less than half of patients know they have CKD stage 3b or 4. Women are less likely to be aware of their CKD in all subgroups. Possible causes are gender-related differences in primary health care (gender bias) or in patient-doctor communication., Competing Interests: Die Autorinnen/Autoren geben an, dass kein Interessenkonflikt besteht., (The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commecial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/).)

Background: Chronic kidney disease (CKD) is responsible for large personal health and societal burdens. Screening populations at higher risk for CKD is effective to initiate earlier treatment and decelerate disease progress. We externally validated clinical prediction models for unknown CKD that might be used in population screening., Methods: We validated six risk models for prediction of CKD using only non-invasive parameters. Validation data came from 4,185 participants of the German Heinz-Nixdorf-Recall study (HNR), drawn in 2000 from a general population aged 45-75 years. We estimated discrimination and calibration using the full model information, and calculated the diagnostic properties applying the published scoring algorithms of the models using various thresholds for the sum of scores., Results: The risk models used four to nine parameters. Age and hypertension were included in all models. Five out of six c-values ranged from 0.71 to 0.73, indicating fair discrimination. Positive predictive values ranged from 15 to 19%, negative predictive values were > 93% using score thresholds that resulted in values for sensitivity and specificity above 60%., Conclusions: Most of the selected CKD prediction models show fair discrimination in a German general population. The estimated diagnostic properties indicate that the models are suitable for identifying persons at higher risk for unknown CKD without invasive procedures., (© 2022. The Author(s).)