Icteric human samples: Icterus index and method of estimating an interference-free value for 16 biochemical analyses

Contrast-enhanced ultrasound-guided percutaneous transhepatic cholangiodrainage is a safe and effective procedure for patients with malignant biliary obstruction and stage 3 chronic kidney disease

OBJECTIVES

This study aimed to validate the efficacy and safety of contrast-enhanced ultrasound-guided percutaneous transhepatic cholangiodrainage (CEUS-PTCD) as a biliary drainage procedure in patients with malignant biliary obstruction and stage 3 chronic kidney disease (CKD3).

MATERIALS AND METHODS

Between January 2019 and December 2023, 634 patients who underwent CEUS-PTCD were retrospectively enrolled in this study. During the procedure, imaging parameters such as the maximum diameter of the dilated bile duct, presence of ascites, detailed findings from CEUS, and clinical outcomes were meticulously recorded. Laboratory results, including serum bilirubin levels, liver function tests, and estimated glomerular filtration rate (eGFR), were evaluated in one day before and three days after procedure. The aforementioned parameters were compared using the paired-sample t test and the Wilcoxon test.

RESULTS

A total of 66 (10.41 %) patients with malignant biliary obstruction and CKD3 were included in the final analysis (median age: 66, range: 30-89 years, 46 males and 20 females). Procedure records indicated that 23 patients (34.8 %) had a maximum biliary duct dilation diameter of ≤ 4 mm, while 5 patients (7.6 %) exhibited mild ascites. Additionally, 24 patients (36.4 %) had ultrasound contrast agent entry into both the biliary duct and bloodstream. All patients successfully achieved external bile drainage following CEUS-PTCD, with no significant complications observed during or after the intervention. Post-procedure, there was a statistically significant reduction in all previously elevated serum bilirubin and liver enzyme levels (P-values were less than 0.05). Furthermore, no statistically significant alterations in eGFR were observed prior to or following CEUS-PTCD across all patients (P = 0.295), including comparisons between groups with and without the ultrasound contrast agent into the bloodstream (P = 0.254).

CONCLUSION

CEUS-PTCD is a safe and effective biliary drainage procedure for patients with malignant biliary obstruction and CKD3.

Definition of icteric interference index for six biochemical analytes

Introduction

Icterus, if not detected, can affect the validity of results delivered by clinical laboratories, leading to erroneous results. This study aims to define bilirubin interference for some biochemical analytes and compare it with the manufacturer's data.

Material and methods

Serum pools prepared with outpatients' samples were spiked with increasing bilirubin concentration (Merck, reference14370, Darmstadt, Germany) up to 513 µmol/L in order to evaluate the bias for the following biochemical analytes: creatinine (CREA), creatine kinase (CK), cholesterol (CHOL), gamma-glutamyltransferase (GGT), high-density lipoprotein cholesterol (HDL), and total protein (TP). For each analyte, six pools of different concentrations were prepared. Measurements were made employing Cobas 8000 analyser c702-502, Roche Diagnostics (Mannheim, Germany). This study employed a study procedure defined by the Spanish Society of Laboratory Medicine.

Results

Obtained bilirubin concentrations producing a negative interference were 103 µmol/L for CHOL, 205 µmol/L for TP and 410 µmol/L for CK, but only for CK values less than 100 U/L. Bilirubin concentrations lower than 513 µmol/L do not produce interference for HDL and GGT. Finally, for the studied bilirubin concentrations, there is no interference for CREA higher than 80 µmol/L.

Conclusion

Icterus interferences have been defined for each analyte, observing differences compared to data provided by the manufacturer. The evidence indicates that each laboratory should evaluate icteric interferences to ensure the high quality of the delivered results, thus benefiting patient care.

Independent Validation and Assay Standardization of Improved Metabolic Biomarker Signature to Differentiate Pancreatic Ductal Adenocarcinoma From Chronic Pancreatitis

BACKGROUND & AIMS

Pancreatic ductal adenocarcinoma cancer (PDAC) is a highly lethal malignancy requiring efficient detection when the primary tumor is still resectable. We previously developed the MxPancreasScore comprising 9 analytes and serum carbohydrate antigen 19-9 (CA19-9), achieving an accuracy of 90.6%. The necessity for 5 different analytical platforms and multiple analytical runs, however, hindered clinical applicability. We therefore aimed to develop a simpler single-analytical run, single-platform diagnostic signature.

METHODS

We evaluated 941 patients (PDAC, 356; chronic pancreatitis [CP], 304; nonpancreatic disease, 281) in 3 multicenter independent tests, and identification (ID) and validation cohort 1 (VD1) and 2 (VD2) were evaluated. Targeted quantitative plasma metabolite analysis was performed on a liquid chromatography-tandem mass spectrometry platform. A machine learning-aided algorithm identified an improved (i-Metabolic) and minimalistic metabolic (m-Metabolic) signatures, and compared them for performance.

RESULTS

The i-Metabolic Signature, (12 analytes plus CA19-9) distinguished PDAC from CP with area under the curve (95% confidence interval) of 97.2% (97.1%-97.3%), 93.5% (93.4%-93.7%), and 92.2% (92.1%-92.3%) in the ID, VD1, and VD2 cohorts, respectively. In the VD2 cohort, the m-Metabolic signature (4 analytes plus CA19-9) discriminated PDAC from CP with a sensitivity of 77.3% and specificity of 89.6%, with an overall accuracy of 82.4%. For the subset of 45 patients with PDAC with resectable stages IA-IIB tumors, the sensitivity, specificity, and accuracy were 73.2%, 89.6%, and 82.7%, respectively; for those with detectable CA19-9 >2 U/mL, 81.6%, 88.7%, and 84.5%, respectively; and for those with CA19-9 <37 U/mL, 39.7%, 94.1%, and 76.3%, respectively.

CONCLUSIONS

The single-platform, single-run, m-Metabolic signature of just 4 metabolites used in combination with serum CA19-9 levels is an innovative accurate diagnostic tool for PDAC at the time of clinical presentation, warranting further large-scale evaluation.

Data on the frequency and causes of icteric interference in clinical chemistry laboratory tests

The presence of elevated levels of bilirubin (icterus) in serum or plasma specimens has the potential to interfere with clinical chemistry and other laboratory assays. Along with hemolysis and lipemia, icterus represents one of the most common endogenous interferences with laboratory tests. There are two common mechanisms by which icterus can cause assay interference. The first common mechanism is spectral interference due to absorption at wavelengths used in assays by bilirubin and/or bilirubin breakdown products. The second common mechanism involves chemical reaction of bilirubin with the reagents used in some enzymatic assays. Most automated clinical chemistry platforms can perform rapid estimates of indices for hemolysis, icterus, and lipemia (HIL), typically by measuring absorbance at wavelengths impacted by these interferences. The data in this article provides results from a detailed 12-month retrospective review of icteric indices and the impact on 114 clinical chemistry assays at an academic medical center in the United States. The data include 414,502 specimens from 94,081 unique patients (51,851 females; 42,230 males), with a total of 2,791,591 discrete clinical chemistry assays performed on the specimens. Detailed chart review was performed for all patients who had one or more specimens with an icteric index of 40 or higher (‘severe icterus’), including determination of the medical diagnoses likely causing icterus and the mortality of these patients within 1 and 3 years following laboratory testing. Data for all specimens include patient location at time of testing (emergency department, inpatient unit, or outpatient site), sex, age, HIL indices, specific clinical chemistry assays performed, and number of times specimens had icteric indices exceeding the icteric index threshold in the package inserts for the clinical chemistry assays performed. The dataset reported is related to the research entitled “Frequency of Icteric Interference in Clinical Chemistry Laboratory Tests and Causes of Severe Icterus” [S. Mainali, A.E. Merrill, M.D. Krasowski, Frequency of icteric interference in clinical chemistry laboratory tests and causes of severe icterus, Pract. Lab. Med. (2021) 27: e00259]

Frequency of icteric interference in clinical chemistry laboratory tests and causes of severe icterus

Objectives

The aims of this study were to identify the causes of severe icterus in an academic medical center patient population and to assess the impact of icterus on clinical chemistry testing using assay package insert thresholds.

Design

and Methods: In this retrospective study at an academic medical center core clinical laboratory, icteric, hemolysis, and lipemia indices were available for all serum and plasma chemistry specimens analyzed on Roche Diagnostics cobas 8000 analyzers over a 12-month period, encompassing 414,502 specimens from 94,081 unique patients (51,851 females; 42,230 males) including children, inpatient, outpatient, and emergency department patients. Extensive chart review was done for all 57 patients (4 pediatric, 53 adult; 534 total specimens) who had one or more samples with an icteric index of 40 or higher (defined as severe icterus).

Results

Specimen icteric index exceeded package insert icteric index thresholds in 0.14% of clinical chemistry assays, with the highest number of instances for creatinine (1358 samples, 0.6% of total tests), total protein (1194 samples, 2.2%), and ammonia (161 samples, 3.9%). The 57 patients with an icteric index of 40 or higher accounted for 49.7% of all instances where the icteric index exceeded the specific assay package insert limit. The most common etiologies of this group of 57 patients were alcohol-related liver disease (34 patients), biliary tract disease (7 patients), and neoplasms (6 patients).

Conclusions

Approximately half of all instances where specimen icteric index exceeded assay package insert thresholds occurred in a small cohort of patients with severe liver/biliary tract disease.

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Specimen icteric indices exceeded package insert icteric index thresholds for 0.14% of clinical chemistry tests ordered at an academic medical center.

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Icteric interference exceeding package insert thresholds had the most overall occurrences for enzymatic creatinine, total protein, and ammonia.

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Only 57 of 94,081 unique patients (0.06%) with severe icterus accounted for nearly half of instances where the icteric index exceeded the package insert limit for a specific assay.

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The small cohort of patients with severe icterus had high mortality generally associated with cirrhosis, biliary disease, or aggressive metastatic cancer.

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Icteric indices exceeding 20 were mostly comprised of patients with predominantly conjugated hyperbilirubinemia.

Development and Validation of Hematocrit Level Measurement in Dried Blood Spots Using Near-Infrared Spectroscopy

BACKGROUND

Dried blood spots (DBSs) have gained recent popularity as a sampling method for therapeutic drug monitoring. For patients, DBS sampling has several advantages over venous blood sampling. However, technical issues primarily influenced by hematocrit levels, interfere with the implementation of this method in daily clinical practice. The results of concentration measurements of drugs that are influenced by hematocrit should be corrected for hematocrit levels. In this article, we developed a fast, nondestructive, near-infrared (NIR)-based method for measuring the hematocrit in DBSs.

METHOD

Using a partial least squares algorithm, an NIR-based quantification method was developed for measuring hematocrit levels of 0.19-0.49 L/L. Residual venous blood of 522 patients was used to build this partial least squares model. The validity of the method was evaluated using 40 patient samples. DBSs were created by adding a small amount (50 µL) of blood on a Whatman filter paper and drying for 24 hours in a desiccator cabinet. The robustness was evaluated by measuring 24 additional samples with a high hemolysis, icterus, and lipemia (HIL) index. The hematocrit values obtained using a Sysmex XN hemocytometry analyzer were used as reference.

RESULTS

The difference between hematocrit measurements obtained with NIR spectroscopy and a hemocytometry analyzer was <15% for the 40 samples. The accuracy (≤9%) and precision (≤7%) for all the quality control samples were within the acceptance criteria of <15%. The intraassay and interassay coefficient of variability was ≤3% and ≤6%, respectively, for the different quality control levels. There were no deviations in the measurements for the samples with high HIL indices. The stability of hematocrit in DBS was up to 14 days for all levels.

CONCLUSIONS

We developed and validated a hematocrit model using NIR spectroscopy. This nondestructive, accurate, and reproducible method has a short analysis time (51 seconds), and can be used to analyze DBS samples stored for up to 2 weeks in a desiccator cabinet.

Evaluation of a new point-of-care testing for creatinine and urea measurement

Point of care testing makes it possible to obtain results in an extremely short time. Recently, radiometer has expanded the panel of tests available on its ABL90 FLEX PLUS blood gas analyzer (ABL90) by adding urea and creatinine. The aim of this study was to verify the performance of these new parameters. This included assessment of imprecision, linearity, accuracy by comparison with central laboratory standard assays and interferences. In addition, clinical utility in a dialysis center was evaluated. Within-lab coefficients of variation were close to 2%. The mean and limits of agreement (mean ± 1.96 SD) of the difference between ABL90 and Roche enzymatic assays on cobas 8000 were 0.5 (from -1.4 to 2.3) mmol/L and -0.9 (from -19.5 to 17.8) µmol/L for urea and creatinine, respectively. The ABL90 enzymatic urea and creatinine assays met the acceptance criteria based on biological variation for imprecision and showed good agreement with central laboratory. The two assays were unaffected by hematocrit variation between 20 and 70%, hemolysis and icterus interferences. It should be noted that the relationship between lab methods and ABL90 was conserved even for high pre-dialysis values allowing easy access to dialysis adequacy parameters (Kt/V) and muscle mass evaluation (creatinine index). Rapid measurement of creatinine and urea using whole blood specimens on ABL90 appears as a fast and convenient method. Analytical performances were in accordance with our expectations without any significant interferences by hemolysis or icterus.

The CONSTANCES Cohort Biobank: An Open Tool for Research in Epidemiology and Prevention of Diseases

“General-purpose cohorts” in epidemiology and public health are designed to cover a broad scope of determinants and outcomes, in order to answer several research questions, including those not defined at study inception. In this context, the general objective of the CONSTANCES project is to set up a large population-based cohort that will contribute to the development of epidemiological research by hosting ancillary projects on a wide range of scientific domains, and to provide public health information. CONSTANCES was designed as a randomly selected sample of French adults aged 18–69 years at study inception; 202,045 subjects were included over an 8-year period. At inclusion, the selected participants are invited to attend one of the 24 participating Health Prevention Centers (HPCs) for a comprehensive health examination. The follow-up includes a yearly self-administered questionnaire, and a periodic visit to an HPC. Procedures have been developed to use the national healthcare databases to allow identification and validation of diseases over the follow-up. The biological collection (serum, lithium heparinized plasma, EDTA plasma, urine and buffy coat) began gradually in June 2018. At the end of the inclusions, specimens from 83,000 donors will have been collected. Specimens are collected according to a standardized protocol, identical in all recruitment centers. All operations relating to bio-banking have been entrusted by Inserm to the Integrated Biobank of Luxembourg (IBBL). A quality management system has been put in place. Particular attention has been paid to the traceability of all operations. The nature of the biological samples stored has been deliberately limited due to the economic and organizational constraints of the inclusion centers. Some research works may require specific collection conditions, and can be developed on request for a limited number of subjects and in specially trained centers. The biological specimens that are collected will allow for a large spectrum of biomarkers studies and genetic and epigenetic markers through candidate or agnostic approaches. By linking the extensive data on personal, lifestyle, environmental, occupational and social factors with the biomarker data, the CONSTANCES cohort offers the opportunity to study the interplays between these factors using an integrative approach and state-of-the-art methods.

Interferences in the measurement of circulating phosphate: a literature review

Background

Inorganic phosphate in blood is currently determined by the reaction with molybdate. This report aims at reviewing conditions underlying spuriously altered levels of circulating inorganic phosphate.

Content

A systematic search of the Excerpta Medica, the National Library Database and the Web of Science database was conducted without language restriction from the earliest publication date available through January 31, 2020.

Summary

For the analysis, 80 reports published in English (n = 77), French (n = 1), German (n = 1) and Spanish (n = 1) were retained. Well-documented pseudohyperphosphatemia was observed in individuals exposed to liposomal amphotericin, in patients affected by a gammopathy, in patients with hyperlipidemia and in patients with hyperbilirubinemia. An unexplained elevated inorganic phosphate level sometimes provided a clue to the diagnosis of a gammopathy. Well-documented cases of pseudohypophosphatemia were observed in patients on large amounts of intravenous mannitol. Finally, pseudohypophosphatemia was occasionally observed on treatment with liposomal amphotericin and in patients with a gammopathy.

Outlook

In order to avoid unnecessary testing and treatment, the phenomenon of spuriously altered inorganic phosphate should be recognized. An unexplained hyperphosphatemia may provide a clue to the diagnosis of a gammopathy or a severe hyperlipidemia.

Establishing hemolysis and lipemia acceptance thresholds for clinical chemistry tests

BACKGROUND

A key component of laboratory medicine is the evaluation of specimen suitability for downstream analytical testing. Accurate identification and characterization of the impact of interferents on clinical chemistry analytes is important for patient care. To empirically assess the influence of hemolysis and lipemia on clinical chemistry tests analyzed on a Roche cobas® c701 system, we evaluated serum pools spiked with increasing concentrations of hemolysate and Intralipid®.

METHODS

Using an interferent acceptance threshold of within ± 10% of the non-hemolyzed or non-lipemic results, 31 routine chemistry analytes were evaluated.

RESULTS

The majority of analytes were determined to have the same or very similar acceptability thresholds as those listed in the vendor package insert. However, several analytes resulted in new thresholds that deviated from manufacturer recommendations (9 higher and 2 lower for lipemia, 7 higher and 6 lower for hemolysis). Samples with high enzyme activities (LDH, ALT, AST, ALP, and CK) were observed to tolerate higher levels of hemolysis, and tiered hemolysis thresholds were established for these enzymes. Independent evaluation of indices is recommended to enable thoughtful implementation of specimen quality criteria and to provide guidance to laboratorians and providers on the nature of these interferences.

Icteric human samples: Icterus index and method of estimating an interference-free value for 16 biochemical analyses

BACKGROUND

Hemolysis, Icterus, and Lipemia constituting the HIL index, are the most common causes of interference with accurate measurement in biochemistry. This study focuses on bilirubin interference, aiming to identify the analyses impacted and proposing a way to predict nominal interference-free analyte concentrations, based on both analyte level and Icterus Index (I_ict ).

METHODS

Sixteen common analytes were studied: alanine aminotransferase (ALT), albumin (ALB), alkaline phosphatase (ALP), amylase (AMY), aspartate aminotransferase (AST), total cholesterol (CHOLT), creatinine (CREA, enzymatic method), fructosamine (FRUC), gamma-glutamyl transferase (GGT), HDL cholesterol (HDLc), total iron (Iron), lipase (LIP), inorganic phosphorus (Phos), total protein (PROT), triglycerides (TG), and uric acid (UA). Both the traditional 10% change in concentrations from baseline and the Total Change Level (TCL) were taken as acceptance limits. Nineteen pools of sera covering a wide range of values were tested on the Cobas® 6000 (Roche Diagnostics). I_ict ranged from 0 to 60.

RESULTS

Eight analytes increased (FRUC and Phos) or decreased (CHOLT, CREA, HDLc, PROT, TG, and UA) significantly when I_ict increased. FRUC, HDLc, PROT, and UA showed a linear relationship when I_ict increased. A non-linear relationship was found for TG, CREA, and for CHOLT; this also depended on analyte levels. Others were not impacted, even at high I_ict .

CONCLUSIONS

A method of estimating an interference-free value for FRUC, HDLc, PROT, Phos, UA, TG, and CREA, and for CHOLT in cases of cholestasis, is proposed. I_ict levels are identified based on analytical performance goals, and equations to recalculate interference-free values are also proposed.