Correction For Dilution Research Articles

Comparing prescribed and delivered doses in ICU patients on continuous renal replacement therapy at King Fahad Hospital Saudi Arabia.

The outcomes of several studies to assess the dose of dialysis during renal replacement therapy (RRT) created confusion among the clinicians to considered that dose of dialysis can influence the outcomes of patients with acute kidney injury (AKI). Suitable dose of CRRT is associated with improved survival in critically ill patients with acute kidney injury (AKI). Among different studies Effluent Volume per weight and unit time (mL/kg/h) used to express prescribed effluent rates, in our study same unit used express the effluent rates. Purpose of this study is to find the difference among dosage of CRRT based on effluent rate prescription and actual delivered effluent rate by monitoring records of dialysis. Study Design: Prospective observational cohort study. Setting: King Fahad Hospital Medina Saudi Arabia. Period: 1st June 2016 to 31st December 2016. Material & Methods: Two hundred acute kidney injury patients admitted in ICU on CRRT at rate of 20ml/kg using pre-filter continuous venovenous hemodia-filtration (CVVHDF), among (AKI) patients prescribed doses were compared with the actual dose with in the duration of 24 hours to find out difference between prescribed and actual dose. Results: Findings of our study shows that. Mean average dose of dialysis delivered per day was only 16 hours which is 21% of prescription of pre-dilution CVVHDF. Patients were receiving 14ml/Kg of continues renal replacement therapy (CRRT) with the lack of 21% dilution correction factor. The average number of hours/day on continuous renal replacement therapy was 14.1±2.41, with a mean flow rate of 1.36±0.31 L/h (averaged over 24 h). The delivered doses were significantly lowered then the prescribed doses with (P < 0.001). 30% of doses was missing during CRRT among patients with acute kidney diseases admitted in ICU at king Fahad hospital Saudi Arabia (P-value <0.001). Conclusions: We concluded that during dialysis patients did not received the prescribed dose in comparison to actual delivered dose which effects the survival of critical ill patients with acute kidney injury.

Degassing at Sabancaya volcano measured by UV cameras and the NOVAC network

We used low-cost Raspberry Pi ultraviolet (UV) cameras to measure sulphur dioxide (SO2) fluxes from Sabancaya volcano, Peru, during eruptive activity on 27 April 2018. Light dilution corrections were made by operating instruments at two distances simultaneously. Estimated SO2 fluxes of 27.1 kgs-1 are higher than previously reported, likely due to the current eruptive episode (ongoing since November 2016). Each eruptive event included frequent (2–3 per minute), ash-rich emissions, forming gas pulses with masses of 3.0–8.2 tonnes SO2. Sustained degassing and lack of overpressure suggest open-vent activity. Mean fluxes are consistent with those measured by a permanent NOVAC station (25.9 kgs-1) located under the plume, with remaining differences likely due to windspeed estimates and sampling rate. Our work highlights the importance of accurate light dilution and windspeed modelling in SO2 retrievals and suggests that co-location of UV cameras with permanent scanning spectrometers may be valuable in providing accurate windspeeds.

StaRdom: Versatile Software for Analyzing Spectroscopic Data of Dissolved Organic Matter in R

The roles of dissolved organic matter (DOM) in microbial processes and nutrient cycles depend on its composition, which requires detailed measurements and analyses. We introduce a package for R, called staRdom (“spectroscopic analysis of DOM in R”), to analyze DOM spectroscopic data (absorbance and fluorescence), which is key to deliver fast insight into DOM composition of many samples. staRdom provides functions that standardize data preparation and analysis of spectroscopic data and are inspired by practical work. The user can perform blank subtraction, dilution correction, Raman normalization, scatter removal and interpolation, and fluorescence normalization. The software performs parallel factor analysis (PARAFAC) of excitation–emission matrices (EEMs), including peak picking of EEMs, and calculates fluorescence indices, absorbance indices, and absorbance slope indices from EEMs and absorbance spectra. A comparison between PARAFAC solutions by staRdom in R compared with drEEM in MATLAB showed nearly identical solutions for most datasets, although different convergence criteria are needed to obtain similar results and interpolation of missing data is important when working with staRdom. In conclusion, staRdom offers the opportunity for standardized multivariate decomposition of spectroscopic data without requiring software licensing fees and presuming only basic R knowledge.

Urine selenium concentration is a useful biomarker for assessing population level selenium status

Plasma selenium (Se) concentration is an established population level biomarker of Se status, especially in Se-deficient populations. Previously observed correlations between dietary Se intake and urinary Se excretion suggest that urine Se concentration is also a potentially viable biomarker of Se status. However, there are only limited data on urine Se concentration among Se-deficient populations. Here, we test if urine is a viable biomarker for assessing Se status among a large sample of women and children in Malawi, most of whom are likely to be Se-deficient based on plasma Se status. Casual (spot) urine samples (n = 1406) were collected from a nationally representative sample of women of reproductive age (WRA, n =741) and school aged children (SAC, n=665) across Malawi as part of the 2015/16 Demographic and Health Survey. Selenium concentration in urine was determined using inductively coupled plasma mass spectrometry (ICP-MS). Urinary dilution corrections for specific gravity, osmolality, and creatinine were applied to adjust for hydration status. Plasma Se status had been measured for the same survey participants. There was between-cluster variation in urine Se concentration that corresponded with variation in plasma Se concentration, but not between households within a cluster, or between individuals within a household. Corrected urine Se concentrations explained more of the between-cluster variation in plasma Se concentration than uncorrected data. These results provide new evidence that urine may be used in the surveillance of Se status at the population level in some groups. This could be a cost-effective option if urine samples are already being collected for other assessments, such as for iodine status analysis as in the Malawi and other national Demographic and Health Surveys.

A comparative assessment of dilution correction methods for spot urinary analyte concentrations in a UK population exposed to arsenic in drinking water

Spot urinary concentrations of environmental exposure biomarkers require correction for dilution. There is no consensus on the most appropriate method, with creatinine used by default despite lacking theoretical robustness. We comparatively assessed the efficacy of creatinine; specific gravity (SG); osmolality and modifications of all three for dilution correcting urinary arsenic. For 202 participants with urinary arsenic, creatinine, osmolality and SG measurements paired to drinking water As, we compared the performance corrections against two independent criteria: primarily, (A) correlations of corrected urinary As and the dilution measurements used to correct them - weak correlations indicating good performance and (B) correlations of corrected urinary As and drinking water As - strong correlations indicating good performance. More than a third of variation in spot urinary As concentrations was attributable to dilution. Conventional SG and osmolality correction removed significant dilution variation from As concentrations, whereas conventional creatinine over-corrected, and modifications of all three removed measurable dilution variation. Modified creatinine and both methods of SG and osmolality generated stronger correlations of urinary and drinking water As concentrations than conventional creatinine, which gave weaker correlations than uncorrected values. A disparity in optima between performance criteria was observed, with much smaller improvements possible for Criterion B relative to A. Conventional corrections – particularly creatinine - limit the utility spot urine samples, whereas a modified technique outlined here may allow substantial improvement and can be readily retrospectively applied to existing datasets. More studies are needed to optimize urinary dilution correction methods. Covariates of urinary dilution measurements still warrant consideration.

Iodine status in western Kenya: a community-based cross-sectional survey of urinary and drinking water iodine concentrations.

Spot urinary iodine concentrations (UIC) are presented for 248 individuals from western Kenya with paired drinking water collected between 2016 and 2018. The median UIC was 271µgL-1, ranging from 9 to 3146µgL-1, unadjusted for hydration status/dilution. From these data, 12% were potentially iodine deficient (< 100µgL-1), whilst 44% were considered to have an excess iodine intake (> 300µgL-1). The application of hydration status/urinary dilution correction methods was evaluated for UICs, using creatinine, osmolality and specific gravity. The use of specific gravity correction for spot urine samples to account for hydration status/urinary dilution presents a practical approach for studies with limited budgets, rather than relying on unadjusted UICs, 24h sampling, use of significantly large sample size in a cross-sectional study and other reported measures to smooth out the urinary dilution effect. Urinary corrections did influence boundary assessment for deficiency-sufficiency-excess for this group of participants, ranging from 31 to 44% having excess iodine intake, albeit for a study of this size. However, comparison of the correction methods did highlight that 22% of the variation in UICs was due to urinary dilution, highlighting the need for such correction, although creatinine performed poorly, yet specific gravity as a low-cost method was comparable to osmolality corrections as the often stated 'gold standard' metric for urinary concentration. Paired drinking water samples contained a median iodine concentration of 3.2µgL-1 (0.2-304.1µgL-1). A weak correlation was observed between UIC and water-I concentrations (R = 0.11).

Comparison of efficiency of techniques for delineating uni-element anomalies from stream sediment geochemical landscapes

This paper compares analyses of raw geochemical data and processed stream sediment geochemical data (i.e., background-corrected and dilution-corrected via the sample catchment basin approach (SCBA)). Both sets of analyses, based on multifractal approach, aimed to identify geochemical anomalies in three study regions in Iran with different geological characteristics and mineralization styles. The results of both analyses were validated for robustness by using the concept of normalized density (ND), which simultaneously considers both mineralized locations and area of anomalous zones. The comparison of the results emphasizes the efficiency of background and dilution correction procedures, which deal with stream sediment geochemical landscapes in the search for mineral deposits. This paper also presents results of discrete (catchment-based) and continuous (interpolation-based) field modelling of stream sediment geochemical dataset per region study. Although interpolation-based field modelling is rapid, time efficient and simple for delineation of geochemical anomalies, the results of discrete-based field modelling of geochemical anomalies are more superior. Therefore, regardless of the mineralization styles and geological settings, the SCBA to identify geochemical anomalies for mineral exploration is efficient.

Community Water Fluoridation and Urinary Fluoride Concentrations in a National Sample of Pregnant Women in Canada.

Background:Fluoride exposures have not been established for pregnant women who live in regions with and without community water fluoridation.Objective:Our aim was to measure urinary fluoride levels during pregnancy. We also assessed the contribution of drinking-water and tea consumption habits to maternal urinary fluoride (MUF) concentrations and evaluated the impact of various dilution correction standards, including adjustment for urinary creatinine and specific gravity (SG).Methods:We measured MUF concentrations in spot samples collected in each trimester of pregnancy from 1,566 pregnant women in the Maternal–Infant Research on Environmental Chemicals cohort. We calculated intraclass correlation coefficients (ICCs) to assess variability in MUF concentrations across pregnancy. We used regression analyses to estimate associations between MUF levels, tea consumption, and water fluoride concentrations as measured by water treatment plants.Results:Creatinine-adjusted MUF values (; milligrams per liter) were almost two times higher for pregnant women living in fluoridated regions () compared with nonfluoridated regions (; ). MUF values tended to increase over the course of pregnancy using both unadjusted values and adjusted values. Reproducibility of the unadjusted and adjusted MUF values was modest (). The municipal water fluoride level was positively associated with creatinine-adjusted MUF (, 95% CI: 0.46, 0.57), accounting for 24% of the variance after controlling for covariates. Higher MUF concentrations correlated with numbers of cups of black ( but not green tea (). Urinary creatinine and SG correction methods were highly correlated () and were interchangeable in models examining predictors of MUF.Conclusion:Community water fluoridation is a major source of fluoride exposure for pregnant women living in Canada. Urinary dilution correction with creatinine and SG were shown to be interchangeable for our sample of pregnant women. https://doi.org/10.1289/EHP3546

Community Water Fluoridation and Urinary Fluoride Concentrations in a National Sample of Pregnant Women in Canada

Background: Fluoride exposure in pregnant women who live in regions with and without community water fluoridation has not been established.Objective: To measure urinary fluoride levels during pregnancy using urinary creatinine and specific gravity (SG) as dilution correction standards.Methods: We measured maternal urinary fluoride (MUF) concentrations in spot samples collected in each trimester of pregnancy from 1566 pregnant women living in ten Canadian cities and enrolled in the &amp;#8220;Maternal-Infant Research on Environmental Chemicals&amp;#8221; cohort. We calculated intraclass correlation coefficients (ICCs) to assess variability in MUF concentrations across pregnancy. We estimated associations between MUF levels, tea consumption, and water fluoride concentrations as measured by water treatment plants using regression analyses.Results: Creatinine-adjusted MUF values (M &amp;#177; SD; mg/L) were almost two-times higher for pregnant women living in fluoridated regions (0.86 &amp;#177; 0.34) compared with non-fluoridated regions (0.46 &amp;#177; 0.50; p&amp;lt;0.001). MUF values had modest reproducibility (ICC &amp;#61; 0.41) and tended to increase over the course of pregnancy. Creatinine-adjusted MUF was positively associated with municipal water fluoride level (B&amp;#61;0.52, 95% CI: 0.46, 0.57), accounting for 24% of the variance after controlling for covariates. Higher MUF concentration correlated with number of cups of black (r &amp;#61; 0.31 to 0.32, p&amp;lt;0.005), but not green tea (r &amp;#61; 0.04 to 0.06). Urinary creatinine and SG correction methods were highly correlated (r &amp;#61; 0.91) and interchangeable in models examining predictors of MUF.Conclusion: Community water fluoridation is a major source of fluoride exposure for pregnant women living in Canada. Urinary dilution correction with creatinine and SG are valid and interchangeable methods for pregnant women.

The Precision and Accuracy of Urinary Creatinine Analysis for Correction of Urine Dilution in Biological Monitoring Measurements

Biomonitoring has been widely used to assess environmental exposure, and spot urine is commonly studied due to its easy sample collection. The variability of urine dilution has been crucial for assessing the exposure magnitude. Previous studies indicated that creatinine-adjusted concentrations are better correlated with the parent chemical concentrations in blood, plasma or serum than unadjusted concentrations. More recent studies have documented problems with creatinine-adjustment in pregnant women and diverse populations because creatinine varies with age, gender, race, body size, and diet.In addition to the inter- and intra-person variability in creatinine, we found significant variability in the testing methods and the testing laboratories. Two immunoassays gave decidedly different concentrations on the same samples in two different laboratories and even had a greater than 35% bias on NIST Standard Reference Materials. In an attempt to standardize the creatinine measurements, both laboratories adopted the same immunoassay.The inter-laboratory relative percent differences (RPD) ranged from 0.3-13.4% with 5.2% median, and the values determined in each laboratory were highly correlated (Pearson correlation coefficient: r&amp;#61;0.98). Although the results were correlated and relatively precise, 15% biases were found between laboratories with values determined by laboratory B being uniformly higher. The directional significant differences were confirmed by paired t-test (p-value&amp;lt;0.001). Thus, a systemic error can occur among different laboratories which might alter the point estimates of central tendency and percentile concentrations.The results show that in addition to the inherent limitations of biological variation in using creatinine-adjustment in biomonitoring, laboratory error from non-standardized measurements can further introduce variation. Taken together, we suggest that the standardized creatinine measurement or cross-laboratories validation is needed.

Characterization of a UV camera system for SO2 measurements from Popocatépetl Volcano

Since 2016, a UV camera records images of the Popocatépetl Volcano for continuous monitoring of the SO2 plume. Five band-pass filters (300a, 300b, 307, 310, 330) with the different bandwidth (BW) of 10 and 25 nm with transmissions centered at 300 nm (BW = 10) nm), 300 nm (BW = 25 nm), 307 nm (BW = 25 nm), 310 nm (BW = 10 nm)and 330 nm (BW = 10 nm) are used for the analysis. In order to fully characterize the filters and improve our knowledge of the errors affecting the results, the UV camera was used together with a UV spectrometer for experiments and measurements. Gas cells with different concentrations were prepared to simulate field conditions and to calibrate the SO2 column images when measuring from a fixed site. Our study is focused on a) applying the required corrections due to vignetting by the instrumentation as well as flattening the light intensity gradients in the field of view, b) determining the effect on the results when using different interference filters, c) applying a simplified light dilution correction and d) performing an a posteriori calibration correction using four interference filters. Our results show that a permanently installed and well-characterized camera, even with the rather long distance from the crater (11.3 km), can provide valuable and reliable information of the SO2 emissions from the Popocatépetl Volcano.

Progress in Automated Urinalysis.

New technological advances have paved the way for significant progress in automated urinalysis. Quantitative reading of urinary test strips using reflectometry has become possible, while complementary metal oxide semiconductor (CMOS) technology has enhanced analytical sensitivity and shown promise in microalbuminuria testing. Microscopy-based urine particle analysis has greatly progressed over the past decades, enabling high throughput in clinical laboratories. Urinary flow cytometry is an alternative for automated microscopy, and more thorough analysis of flow cytometric data has enabled rapid differentiation of urinary microorganisms. Integration of dilution parameters (e.g., creatinine, specific gravity, and conductivity) in urine test strip readers and urine particle flow cytometers enables correction for urinary dilution, which improves result interpretation. Automated urinalysis can be used for urinary tract screening and for diagnosing and monitoring a broad variety of nephrological and urological conditions; newer applications show promising results for early detection of urothelial cancer. Concomitantly, the introduction of matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) has enabled fast identification of urinary pathogens. Automation and workflow simplification have led to mechanical integration of test strip readers and particle analysis in urinalysis. As the information obtained by urinalysis is complex, the introduction of expert systems may further reduce analytical errors and improve the quality of sediment and test strip analysis. With the introduction of laboratory-on-a-chip approaches and the use of microfluidics, new affordable applications for quantitative urinalysis and readout on cell phones may become available. In this review, we present the main recent developments in automated urinalysis and future perspectives.

Dilution correction for dynamically influenced urinary analyte data

Urinary analyte data has to be corrected for the sample specific dilution as the dilution varies intra- and interpersonally dramatically, leading to non-comparable concentration measures. Most methods of dilution correction utilized nowadays like probabilistic quotient normalization or total spectra normalization result in a division of the raw data by a dilution correction factor. Here, however, we show that the implicit assumption behind the application of division, log-linearity between the urinary flow rate and the raw urinary concentration, does not hold for analytes which are not in steady state in blood. We explicate the physiological reason for this short-coming in mathematical terms and demonstrate the empirical consequences via simulations and on multiple time-point metabolomic data, showing the insufficiency of division-based normalization procedures to account for the complex non-linear analyte specific dependencies on the urinary flow rate. By reformulating normalization as a regression problem, we propose an analyte specific way to remove the dilution variance via a flexible non-linear regression methodology which then was shown to be more effective in comparison to division-based normalization procedures. In the progress, we developed several, easily applicable methods of normalization diagnostics to decide on the method of dilution correction in a given sample. On the way, we identified furthermore the time-span since last urination as an important variance factor in urinary metabolome data which is until now completely neglected. In conclusion, we present strong theoretical and empirical evidence that normalization has to be analyte specific in dynamically influenced data. Accordingly, we developed a normalization methodology for removing the dilution variance in urinary data respecting the single analyte kinetics.

Volcanic Plumes: Impacts on the Atmosphere and Insights into Volcanic Processes

Here we introduce a Special Issue of Geosciences focused on the scientific research field of ‘Volcanic Plumes: Impacts on the atmosphere and insights into volcanic processes’ [...]

Improved phosphometabolome profiling applying isotope dilution strategy and capillary ion chromatography-tandem mass spectrometry

The phosphometabolome is comprised of all phosphorylated metabolites including the major metabolite classes sugar phosphates and nucleoside phosphates. Phosphometabolites are invaluable in any cell as a part of primary- and energy- metabolism, and as building blocks in the biosynthesis of macromolecules. Here, we report quantitative profiling of the phosphometabolome by applying capillary ion chromatography-tandem mass spectrometry (capIC-MS/MS), ensuring improved chromatographic separation, robustness and quantitative precision. Baseline separation was achieved for six out of eight tested hexose phosphates. Quantitative precision and reproducibility was improved by introducing a fully uniformly (U) 13C–labeled biological extract and applying an isotope dilution (ID) correction strategy. A 13C–labeled biological extract does in principle contain internal standards (IS) for all metabolites, but low abundant metabolites pose a challenge, and solutions to this are discussed. The extreme reproducibility and reliability of this capIC-MS/MS method was demonstrated by running the instrumentation continuously for ten days.

Measurement of total Transcobalamin employing a commercially available assay for Active B12

IntroductionVitamin B12 deficiency is mostly caused by insufficient gastro-intestinal absorption and in rare conditions by Transcobalamin (TC) deficiency. Unsaturated Transcobalamin (apoTC) can be measured by a binding assay using radiolabeled cobalamin. The Active B12 test analyzes saturated Transcobalamin (holoTC) and we hypothesize that this test can be used to measure total TC by additional in vitro saturation with cobalamin. MethodsSerum was saturated in vitro (16 times dilution) with a cyanocobalamin solution and total TC was selectively measured with the Abbott Active B12 test. ApoTC was calculated by subtracting endogenous holoTC from total TC after correction for dilution. Linearity was determined with a pool serum dilution series. Precision was investigated according to the CLSI EP15 protocol. Method comparison was performed against a binding assay using radiolabeled cobalamin. Reference values were determined in 100 healthy controls. ResultsThe method was linear in the range of 240 to 1933pmol/L (R2=0.997, lack of fit F=1.61). Precision of low- and high-pool total TC in serum were; 5.2% and 4.3% respectively. Method comparison against a radiolabeled cobalamin binding assay showed a proportional bias of 30% (y=0.70x+126). Total TC reference values were determined at 500–1276pmol/L. ConclusionWe describe a rapid method to quantify total TC, which can be implemented on routine platforms using commercial Active B12 tests. In addition, apoTC can be assessed by subtracting endogenous holoTC concentration which can be measured in the same run, securing the same calibration level for all three parameters (holoTC, apoTC and total TC). This method is applicable in clinical diagnostics and in larger epidemiological studies.

Improved detection of anomalous catchment basins by incorporating drainage density in dilution correction of geochemical residuals

In exploration for mineral deposits using stream sediment samples, a phenomenon known as dilution of metal content originating from mineralized sources should be taken into account. Dilution occurs when stream sediments originating from upstream mineralized and non-mineralized areas are mixed during transport and deposition. In the sample catchment basin approach, dilution correction is accomplished by employing Hawkes's equation (1976). Catchment area size is the correction factor used in the Hawkes's equation to correct geochemical residuals for dilution. However, the upstream area of each stream sediment sample is representative of the hydrological response and dilution capability of a drainage basin. In the present research, the Hawkes's equation was modified by incorporating drainage density of catchment basin to correct geochemical residuals for dilution. The existing and new equations were applied to stream sediment data from Iran. The results were compared using known occurrences of Au mineralization as validation points. This showed the superiority of the new technique using drainage density as a factor for correcting geochemical residuals against dilution.

Fluoride exposure and reported learning disability diagnosis among Canadian children: Implications for community water fluoridation.

Recent studies have connected increased fluoride exposure with increased risk of neurodevelopmental-related outcomes, such as ADHD (attention deficit hyperactivity disorder) and lower IQ in children. Our primary objective was to examine the association between fluoride exposure and reported diagnosis of a learning disability among a population-based sample of Canadian children aged 3-12 years. We analyzed data from Cycles 2 and 3 of the Canadian Health Measures Survey. Four measures of fluoride exposure were available: 1) urinary fluoride (μmol/L), 2) creatinine-adjusted urinary fluoride (μmol/mmol), 3) specific gravity-adjusted urinary fluoride (μmol/L), and 4) fluoride concentration of tap water (mg/L) (Cycle 3 only). Diagnosis of a learning disability (yes/no) was based on parental- or self-report. Associations were examined using logistic regression (where possible), unadjusted and adjusted for covariates. When Cycles 2 and 3 were examined separately, reported learning disability diagnosis was not significantly associated with any measure of fluoride exposure in unadjusted or adjusted models. When Cycles 2 and 3 were combined, a small but statistically significant effect was observed such that children with higher urinary fluoride had higher odds of having a reported learning disability in the adjusted model (p = 0.03). However, the association was not observed in models that used creatinine-adjusted urinary fluoride and specific gravity-adjusted urinary fluoride, which are believed to be more accurate measures due to their correction for urinary dilution. Overall, there did not appear to be a robust association between fluoride exposure and parental- or self-reported diagnosis of a learning disability among Canadian children.

Two statistical criteria to choose the method for dilution correction in metabolomic urine measurements

Introduction Different normalization methods are available for urinary data. However, it is unclear which method performs best in minimizing error variance on a certain data-set as no generally applicable empirical criteria have been established so far.

The true sample catchment basin approach in the analysis of stream sediment geochemical data

The Sample Catchment Basin Approach (SCBA) is one of the techniques widely employed in the analysis of stream sediment geochemical data and delineation of anomalous catchments. However, this method fails to take into account the real catchment basin boundaries of each sample by incorporating only the incremental area between two adjacent samples. In other words, the SCBA incorrectly assumes that the geochemistry of every sample catchment within a drainage is independent from upstream sample catchment(s) feeding into this drainage. The chemical composition of sediment at the basin outlet originates from the whole basin upstream and not the incremental area as postulated in the SCBA. Consequently, the calculated background values for various lithologies and the background value for the element of interest at the basin outlet might be far from reality.This study used a True Sample Catchment Basin Approach (TSCBA), that reflects the true catchment boundary of every stream sediment sample, and in which all calculations are carried out on the premise that this boundary and the true area affect the composition of each sample. The results obtained from the application of both the SCBA and TSCBA to a gold endowed study area in western Iran clearly illustrated the superiority of the TSCBA over the SCBA. In addition, this study demonstrated the advantage of using the modified dilution correction equation of Mokhtari and Garousi Nezhad (2015), as compared to the existing Hawkes’s equation commonly used for dilution correction of residual values.