Bias, the unfinished symphony

In laboratory medicine, mathematical equations are frequently used to calculate various parameters including bias, imprecision, measurement uncertainty, sigma metric (SM), creatinine clearance, LDL-cholesterol concentration, etc. Mathematical equations have strict limitations and cannot be used in all situations and are not open to manipulations. Recently, a paper “Bias estimation for Sigma metric calculation: Arithmetic mean versus quadratic mean” was published in Biochemia Medica. In the paper, the author criticized the approach of taking the arithmetic mean of the multiple biases to obtain a single bias and proposed a quadratic method to estimate the overall bias using external quality assurance services (EQAS) data for SM calculation. This approach does not fit the purpose and it should be noted that using the correct equation in calculations is as important as using the correct reagent in the measurement of the analytes, therefore before using an equation, its suitability should be checked and confirmed

The impact of oil prices on oil-gas stock returns: A fresh evidence from the covid-affected countries

The effects of oil price exposure of oil-gas sectors of the countries largely affected by Covid-19 is analyzed with a time-varying parameter model. Estimation results suggest that market risk of all countries’ oil-gas sector excluding China has increased remarkably compared to the period before the spread of the virus. Positive and significant effects of the oil price factor become negative and significant for most countries during the pandemic. The results further indicate that the oil-gas sector of China is not affected by the outbreak of Covid-19, even though the virus has first appeared in that country. © 2021, Bucharest University of Economic Studies. All rights reserved

The impact of central bank digital currency news on the stock and cryptocurrency markets: Evidence from the TVP-VAR model

This study employs a non-linear framework to investigate the impacts of central bank digital currency (CBDC) news on the financial and cryptocurrency markets. The time-varying vector autoregressive (TVP-VAR) model developed by Primiceri (2005) is estimated based on weekly data from the first week of January 2015 to the last week of December 2021. The vector of endogenous variables in the VAR estimation contains the Central Bank Digital Currency uncertainty index (CBDCU), cryptocurrency policy uncertainty index, S&P 500 index, VIX, and Bitcoin price. The TVP-VAR model’s time-varying responses demonstrated that the reactions of the cryptocurrency market to central bank digital currency announcements vary remarkably over time. The impacts of the CBDC shocks on the financial market have been increasingly visible during the COVID-19 pandemic. According to the time-varying forecast error decompositions, CBDCU and VIX shocks have accounted for most of the variance in cryptocurrency uncertainty and Bitcoin return shocks, notably during the COVID-19 period

The Importance Of Financial Conditions on the Functionning Of Monetary Transmission Mechanisms: Evidences From Tvp-Var Models

Bu makalede Türkiye’de parasal aktarım mekanizmalarındaki değişimin finansal koşulların rolü dikkate alınarak incelenmesiamaçlanmaktadır. Bu çerçevede, parasal değişkenler ve finansal koşulların fiyatlar ve iktisadi aktivite üzerindeki etkileri zamanladeğişen parametreli vektör otoregresif (TVP-VAR) modellerin tahmininden elde edilen etki-tepki fonksiyonları ile analizedilmiştir. Sonuçlar aktarım mekanizmalarının işleyişinin zaman içinde önemli ölçüde değiştiğini göstermektedir. Fiyatlarınfaiz oranı şoklarına 2006 yılından sonra negatif ve anlamlı tepki vermesi; faiz oranı kanalının açık enflasyon hedeflemesinegeçiş ile birlikte etkin bir şekilde çalıştığını ima etmektedir. Finansal koşullar endeksine verilen şoklar özellikle finansal krizdönemlerinde iktisadi aktivite üzerinde pozitif ve anlamlı etkilere sahiptir. Bu nedenle söz konusu değişken iktisadi aktiviteniniyi bir öngörücüsü olarak dikkate alınabilir.This article aims to investigate the evolution of monetary transmission channels in Turkey by taking into account the role of financial conditions. In this context, the impacts of monetary variables and financial conditions on the prices and economic activity have been analyzed through impulse-response functions obtained from the estimation of time-varying vector autoregressive (TVP-VAR) models. The results suggest that the functioning of transmission channels has changed remarkably over time. The evidence on the negative and significant impact of interest rate shocks on the prices after 2006 indicates that interest rate channel is functioning efficiently with the adoption of explicit inflation targeting policy. The shocks in financial conditions index have a positive and significant impact on economic activity especially during the periods of financial crises. Therefore this measure can be considered as a good predictor of economic activity

Indirect Reference Intervals Estimated from Hospitalized Population for Thyrotropin and Free Thyroxine

Aim To establish indirect reference intervals from patient results obtained during routine laboratory work as an alternative to laborious and expensive producing of their own reference range values according to international instructions. Methods All results for thyrotropin (TSH) and free thyroxine (T4) that were stored in our laboratory information system between 2004 and 2008 were included in this study. After a logarithmic transformation of the raw data, outliers were excluded. Non-parametric reference intervals were estimated statistically after visual observation of the distribution using stem-and-leaf plots and histograms. A standard normal deviation test was performed to test the significance of differences between sub-groups. Results There was no significant difference in serum TSH or free T4 concentrations between male and female participants. Because no differences were found within the time span of the study, combined reference intervals were calculated. Indirect reference values were 0.43-3.93 mU/L for TSH and 11.98-21.33 pmol/L for free T4. Conclusion Using patient laboratory data values is a relatively easy and cheap method of establishing laboratoryspecific reference values if skewness and kurtosis of the distribution are not too large

Oil prices and sectoral stock returns in the BRICS-T countries: A time-varying approach

This paper investigates how exchange rates and oil prices have affected sectoral stock returns in the BRICS-T countries over the period from 2 January 2001 to 22 March 2021. Following the estimation of a benchmark linear model, Bai and Perron (2003) tests are carried out in each case to identify structural breaks, and then a state-space model with time-varying parameters is also estimated. The analysis shows that oil prices have a significant, positive effect on the energy sectors of all BRICS-T countries except India; a negative one on the industrial sectors of all countries except Turkey; a negative one on the financial sectors of Brazil, Russia, India, and South Africa; a negative one on the transportation sectors of India and Turkey and a positive one on that of Russia; finally, the most significant effect is on the chemicals sector, though it varies across countries. The subsamples and time-varying estimates indicate that exchange rate returns have a larger influence than oil price returns. Because energy-dependent sectors are vulnerable to global volatility, appropriate energy regulations should be implemented to reduce risk

Within- and between-subject biological variation data for tumor markers based on the European Biological Variation Study

Postponed access: the file will be available after 2022-05-10Objectives: Reliable biological variation (BV) data are required for the clinical use of tumor markers in the diagnosis and monitoring of treatment effects in cancer. The European Biological Variation Study (EuBIVAS) was established by the EFLM Biological Variation Working Group to deliver BV data for clinically important measurands. In this study, EuBIVAS-based BV estimates are provided for cancer antigen (CA) 125, CA 15-3, CA 19-9, carcinoembryonic antigen, cytokeratin-19 fragment, alpha‐fetoprotein and human epididymis protein 4. Methods: Subjects from five European countries were enrolled in the study, and weekly samples were collected from 91 healthy individuals (53 females and 38 males; 21–69 years old) for 10 consecutive weeks. All samples were analyzed in duplicate within a single run. After excluding outliers and homogeneity analysis, the BVs of tumor markers were determined by CV-ANOVA on trend-corrected data, when relevant (Røraas method). Results: Marked individuality was found for all tumor markers. CYFRA 21-1 was the measurand with the highest index of individuality (II) at 0.67, whereas CA 19-9 had the lowest II at 0.07. The CV I s of HE4, CYFRA 21-1, CA 19-9, CA 125 and CA 15-3 of pre- and postmenopausal females were significantly different from each other. Conclusions: This study provides updated BV estimates for several tumor markers, and the findings indicate that marked individuality is characteristic. The use of reference change values should be considered when monitoring treatment of patients by means of tumor markers.publishedVersio

Within- and between-subject biological variation data for serum zinc, copper and selenium obtained from 68 apparently healthy Turkish subjects

Postponed access: the file will be available after 2022-10-22Objectives: Trace elements (TrEL) are nutritionally essential components in maintaining health and preventing diseases. There is a lack of reliable biological variation (BV) data for TrELs, required for the diagnosis and monitoring of TrEL disturbances. In this study, we aimed to provide updated within- and between-subject BV estimates for zinc (Zn), copper (Cu) and selenium (Se). Methods: Weekly serum samples were drawn from 68 healthy subjects (36 females and 32 males) for 10 weeks and stored at −80 °C prior to analysis. Serum Zn, Cu and Se levels were measured using inductively-coupled plasma mass spectrometry (ICP-MS). Outlier and variance homogeneity analyses were performed followed by CV-ANOVA (Røraas method) to determine BV and analytical variation estimates with 95% CI and the associated reference change values (RCV) for all subjects, males and females. Results: Significant differences in mean concentrations between males and females were observed, with absolute and relative (%) differences for Zn at 0.5 μmol/L (3.5%), Cu 2.0 μmol/L (14.1%) and Se 0.06 μmol/L (6.0%). The within-subject BV (CVI [95% CI]) estimates were 8.8% (8.2–9.3), 7.8% (7.3–8.3) and 7.7% (7.2–8.2) for Zn, Cu and Se, respectively. Within-subject biological variation (CVI) estimates derived for male and female subgroups were similar for all three TrELs. Marked individuality was observed for Cu and Se. Conclusions: The data of this study provides updated BV estimates for serum Zn, Cu and Se derived from a stringent protocol and state of the art methodologies. Furthermore, Cu and Se display marked individuality, highlighting that population based reference limits should not be used in the monitoring of patients.publishedVersio

The frequency of Duchenne muscular dystrophy/Becker muscular dystrophy and Pompe disease in children with isolated transaminase elevation: results from the observational VICTORIA study

IntroductionElevated transaminases and/or creatine phosphokinase can indicate underlying muscle disease. Therefore, this study aims to determine the frequency of Duchenne muscular dystrophy/Becker muscular dystrophy (DMD/BMD) in male children and Pompe disease (PD) in male and female children with isolated hypertransaminasemia.MethodsThis multi-center, prospective study enrolled patients aged 3–216 months with serum alanine transaminase (ALT) and/or aspartate transaminase (AST) levels >2× the upper limit of normal (ULN) for ≥3 months. Patients with a known history of liver or muscle disease or physical examination findings suggestive of liver disease were excluded. Patients were screened for creatinine phosphokinase (CPK) levels, and molecular genetic tests for DMD/BMD in male patients and enzyme analysis for PD in male and female patients with elevated CPK levels were performed. Genetic analyses confirmed PD. Demographic, clinical, and laboratory characteristics of the patients were analyzed.ResultsOverall, 589 patients [66.8% male, mean age of 63.4 months (standard deviation: 60.5)] were included. In total, 251 patients (188 male and 63 female) had CPK levels above the ULN. Of the patients assessed, 47% (85/182) of male patients were diagnosed with DMD/BMD and 1% (3/228) of male and female patients were diagnosed with PD. The median ALT, AST, and CPK levels were statistically significantly higher, and the questioned neurological symptoms and previously unnoticed examination findings were more common in DMD/BMD patients than those without DMD/BMD or PD (p < 0.001).DiscussionQuestioning neurological symptoms, conducting a complete physical examination, and testing for CPK levels in patients with isolated hypertransaminasemia will prevent costly and time-consuming investigations for liver diseases and will lead to the diagnosis of occult neuromuscular diseases. Trial RegistrationClinicaltrials.gov NCT04120168