BACKGROUND:Capillary self-collection (CSC) devices allow patients to collect blood samples at home, potentially reducing outpatient phlebotomy visits. This study aimed to (a) assess the patient experience with multiple commercially available CSC devices; (b) determine which laboratory tests are commonly ordered together, which could reduce the need for appointments; and (c) evaluate the analytical performance of these tests using CSC samples. METHODS:User experience for 3 CSC devices was evaluated. Clinical feasibility was determined by comparing test results in paired sera collected by venipuncture (VP) and CSC devices. VP samples were centrifuged within 2 h and tested immediately. CSC sera were centrifuged and tested both immediately and after delayed processing to simulate shipping temperature extremes (-20°C or 40°C). Basic metabolic panel, lipid panel, thyroid function cascade, and prostate-specific antigen were evaluated. Differences between VP and CSC collections were characterized according to their statistical and clinical differences. RESULTS:Patients reported CSC devices were easy to use and painless. Clinically significant differences between VP and CSC sera processed immediately were limited to potassium and bicarbonate. Following delayed processing of CSC serum samples (48 h at room temperature), clinically significant differences in potassium, bicarbonate, and glucose were observed. Frozen samples could not be analyzed. A 48 h delay at 40°C caused clinically significant differences in all analytes except creatinine, lipid panel, prostate-specific antigen, and the thyroid cascade. CONCLUSION:Potassium, bicarbonate, and glucose were not stable at room temperature in CSC sera. CSC serum specimens may be a viable option but require analyte-specific evaluation and consideration of transportation conditions.

BACKGROUND:Dipeptidyl peptidase 3 (DPP3) is a peptidase released from dying cells. It cleaves proteins in the renin-angiotensin pathway, which can result in hemodynamic instability. At elevated concentrations DPP3 is associated with worse outcomes, particularly in patients with shock. Herein we describe the assay performance of a DPP3 assay (4TEEN4 Pharmaceuticals GmbH) in human plasma. METHODS:DPP3 concentration was measured using the DPP3 immunoluminometric assay (4TEEN4 Pharmaceuticals GmbH) and the signal was read using a luminometer (Berthold Centro LB963). Analytical performance was established for precision, linearity, accuracy, detection limit, analytical specificity, reference interval, kit lot-to-lot comparison, specimen type, and sample stability. RESULTS:Limit of detection was verified at 1.6 ng/mL in EDTA plasma with a coefficient of variation (CV) of <10%. Precision studies revealed a CV ≤ 6% at 28.5 ng/mL and 59.4 ng/mL and comparability with a manufacturer performed assay was demonstrated between 7.7 and 195.2 ng/mL. An upper 97.5% limit of 22 ng/mL without age or sex associations was verified in healthy donors. The assay was not susceptible to interference from lipemia or bilirubin. However, measured DPP3 concentrations increased linearly with increasing hemolysis. DPP3 concentrations are stable in EDTA plasma for up to 24 h and at least 11 months when stored ambient or at -80°C, respectively. CONCLUSIONS:DPP3 can be measured precisely in EDTA plasma using the immunoluminometric DPP3 assay. Given the potential clinical use of DPP3 in critical care patients, caution should be taken to avoid inducing pre-analytical hemolysis during sample collection.

BACKGROUND:Direct measurement of low-density lipoprotein cholesterol (LDL-C) is widely used and recommended by professional society guidelines despite its potential limitations in patients with hypertriglyceridemia and low LDL-C. This study evaluated the performance of 3 direct LDL-C (LDL-CD) assays, 2 modern LDL-C calculation methods [LDL-C Martin (LDL-CM), LDL-C modified Sampson (LDL-CS)] and the conventional Friedewald (LDL-CF) method against the reference method, beta-quantification (LDL-CBQ). METHODS:A total of 181 remnant sera from patients with standard lipid panel orders or from patients with LDL-CBQ orders with triglycerides (TG) ≥ 400 mg/dL (4.5 mmol/L), or with TG ≥ 150 mg/dL (1.69 mmol/L) and LDL-C < 70 mg/dL (1.8 mmol/L) were included. LDL-CD and lipid panel data were gathered from Abbott Alinity, Roche Cobas, and Siemens Atellica platforms. RESULTS:LDL-CD among the 3 platforms showed a median CV of 11.2%. In patients with TG <400 mg/dL, LDL-CM and LDL-CS demonstrated less bias and less misclassification at the clinical decision LDL-C levels than LDL-CF or LDL-CD. In the 400 to 800 mg/dL (9.0 mmol/L) TG group, LDL-CS was superior to LDL-CD or LDL-CM in accuracy. When TG is ≥ 800 mg/dL, LDL-CD (Roche) showed substantial bias from LDL-CBQ while LDL-CS (Roche) showed smaller but significant bias. CONCLUSIONS:In summary, LDL-CD or LDL-CF showed little advantage over the 2 modern LDL-C calculation methods. LDL-CS showed the best overall correlation with LDL-CBQ and therefore is recommended to replace LDL-CF and potentially LDL-CD when making clinical decisions in patients with low LDL-C and hypertriglyceridemia.

BACKGROUND:Low-density lipoprotein cholesterol (LDL-C) is directly associated with coronary artery disease (CAD) risk. Subfractionation of LDL enables differentiation between large-buoyant LDL (>20.5 nm) and small-dense LDL (≤20.5 nm). Small-dense LDL reportedly increases CAD risk, as do LDL-C and LDL particle (LDL-P) concentrations. Nuclear magnetic resonance spectroscopy (NMR) reports LDL-C, LDL-P, and LDL size (LDL-s). We investigated associations between these outputs and their agreement on CAD risk information. METHODS:Associations between LDL-P, LDL-C, and LDL-s measured by NMR were evaluated in serum from clinically ordered samples (n = 26 710), and a subset of patients with CAD evaluation from coronary angiography (n = 356). Correlations were determined using Spearman ρ, and clinical classifications were compared using the following thresholds for increased risk: LDL-C > 160 mg/dL, LDL-P > 1600 nmol/L, and LDL-S < 20.5 nm. RESULTS:The large laboratory NMR data set showed LDL-C was highly correlated with LDL-P (ρ = 0.87), and moderately with LDL-s (ρ = 0.51). Correlation between LDL-P and LDL-s was weakest (ρ = 0.21). When comparing pairwise high- and low-risk laboratory values, concordant values were observed in 99.8%, 43%, and 25% of cases for LDL-P/LDL-C, LDL-s/LDL-P, and LDL-C/LDL-s, respectively. In patients with angiography and NMR results, CAD was diagnosed in 40% (6/15) of patients with concordant high-risk LDL-C and small-dense LDL-s in the smaller patient cohort, but only 19% (6/31) of CAD-positive patients with high-risk LDL-C had small-dense LDL-s. CONCLUSIONS:LDL-s and LDL-C are frequently discordant at established LDL-C risk cutoffs. CAD diagnosis was found in similar numbers regardless of LDL-s phenotype.

Many laboratories utilize direct LDL-C assays as part of a reflex protocol at TG >400 mg/dL. Despite the cost associated with the direct LDL-C testing in place of freely available calculations, some laboratories still prefer direct LDL-C assay as part of lipid panel. This approach is followed regardless of the patient's LDL-C or TG levels. However, Miller et al. have shown biases with direct LDL-C assays, often leading to the overestimating of LDL-C in dyslipidemia patients (7). Importantly, their analytical performance in the current context of potent lipid-lowering therapies and stringent LDL-C target levels have remained insufficiently evaluated. It is notable that direct LDL-C assays are also susceptible to discrepancies due to different methodologies and inherent Although the newer LDL-C equations have been independently verified to calculate LDL-C up to TG 800 mg/dL with reasonable accuracy compared with direct LDL-C measurements in different populations (13)(14)(15), at TG levels >500 mg/dL, the clinical priority, in these cases, should be to first reduce the elevated TG level to prevent acute pancreatitis. Given this clinical need and the relatively better performance of the new calculations-based LDL-C estimations at even higher TG levels (Sampson-NIH, up to 800 mg/dL) and lower LDL-C levels (Martin/Hopkins equation, LDL-C <70 mg/dL), it is apparent that fewer patients will only require reflexive direct LDL-C measurements.However, it must be noted that no calculation method is perfect, and direct measurement may still be necessary in some cases, particularly when precise quantification of very low LDL-C levels is critical for clinical decision-making. Notably, in case of rare lipid disorders as in type III hyperlipidemia, the FW equation performs poorly due to inaccurate VLDL-C estimation. However, the Martin/Hopkins equation uses an adjustable factor for the TG:VLDL-C ratio, which may provide more accurate estimates in atypical lipid profiles. Nevertheless, they may still have limitations in accurately estimating LDL-C in type III hyperlipidemia due to the condition's unique lipid profile and an accumulation of remnant lipoproteins. Also, in case of post-prandial conditions, unlike the FW equation, which is limited to fasting samples, the newer equations perform equally well in both fasting and non-fasting samples. Thus, while these newer equations offer improvements over the FW equation and can largely curtail the need for reflexive direct LDL-C measurements, they may not eliminate it entirely, especially for very high TG levels (>800 mg/dL), extremely low levels of LDL-C (below 40 mg/dL), or rare lipid disorders. However, it is important to know that direct LDL-C measurements can also be discordant, particularly in patients with high cardiovascular risk and/or dyslipidemia (7). Table 1 summarizes different LDL-C estimation methods comparison.Given that ADLM and other associations have also acknowledged the strength of newer equations, it is important to address why are we still stuck in the old era and still using the FW equation? Recent informal surveys while indicating a slight increase in adoption of the newer equations, the uptake remains still lukewarm. This raises critical questions: What are the barriers to implementing the new LDL-C equations? Why does the reluctance to move on from the FW equation persist? Is it driven by convenience or perceived complications?We believe the primary reason lies in the convenience of sticking to routine practices and a strong reluctance to change, as the FW equation has been entrenched in clinical use for over 5 decades now. This indeed is also largely fueled by the absence of universal guidelines. Without a clear consensus about how new equations may benefit patients, practitioners and facilities may adopt "if it's not broken, don't fix it" approach and continue with established practices.One of the factors hindering the implementation of new equations, particularly, the MH equation is the prevalent misconception that it is copyrighted and would require a licensing fee for its commercial use. However, it has been recently clarified that the MH equation is royalty-free, addressing this concern. Additionally, some confusion may linger about the term "free" in "royalty-free", as it could be interpreted that it is free only from ongoing royalties but still require a significant one-time licensing fee or other specific licensing terms. Recently, Johns Hopkins University has abandoned the patent application to facilitate the use of their equation without intellectual property restrictions (16). Notably, this decision means that this formula is allowed for broader access and application and can be used freely or even modified without any licensing barriers. Thus, the previously misconstrued concern regarding the "no royalty-free" notion is no longer an issue for the transition to using MH equation. Furthermore, despite some concern about the complexity of implementing the MH equation, Johns Hopkins has made this equation more readily accessible in formats that can be seamlessly integrated into LIS and middleware systems like Data Innovations. Laboratories are encouraged to contact JHTT-Communications@jh.edu and smart100@jhmi.edu for assistance with this process (16). Indeed, they have gone a step further and willing to share line-by-line sample code with labs/health systems that are intending to implement their equation. This approach allows faster, more convenient implementation, with each step in the code visible and modifiable for adaptability across LIS platforms and lab protocols. Besides, it can foster collaboration and troubleshooting through peer-reviewed code snippets. Indeed, the MH equation's ease of implementation is exemplified by its increasing adoption in laboratories While these recent changes reflect the growing recognition of the value of the new LDL-C equations and there is now momentum to move towards these next-gen equations, the transition is still far from complete. Although it must be acknowledged that FW equation have served well for decades, its well-known negative bias contributes to the undertreatment of patients, which is a major issue with lipid-lowering therapy (22).Whatever the reason for its ongoing use, be it convenience, familiarity, and or the perceived complexity of change, it is becoming increasingly untenable to persist with the FW equation given the crucial role that LDL-C plays in the management of cardiovascular disease, a leading worldwide cause of death and morbidity. Indeed, in our view it is long past due to break "free" from the conservative mindset and adopt one of the newer "free" LDL-C equations, specifically the Martin/Hopkins or Sampson-NIH.

Key PointsStudies on GFR assessment in people with cancer are needed.In this study, the creatinine-cystatin C equations performed better than other equations, and this was observed in solid and hematological cancers.Our findings give support to the preferential use of creatinine and cystatin C-based equations in people with cancer.BackgroundGFR assessment is important in clinical practice with implications for diagnosis, prognostication, and drug dosing. People with cancer are at risk of imprecision in GFR estimation. This cross-sectional study evaluated the performance of various creatinine and cystatin C-based equations in comparison with measured GFR (mGFR) in people with cancer.MethodsWe retrieved data for all adult patients who had mGFR by urinary iothalamate clearance between 2011 and 2023 at Mayo Clinic and use of an electronic health record diagnosis code for cancer within 2 years before mGFR. The CKD Epidemiology Collaboration (CKD-EPI), European Kidney Function Consortium, and Cockcroft-Gault equations were computed, along with performance metrics (bias, precision, and root mean square error [RMSE]. Confidence intervals were generated by bootstrapping, and analysis were stratified by solid and hematological cancers.ResultsFrom all adults with cancer and mGFR, 1145 had both creatinine and cystatin C available within 7 days of mGFR. Among all equations, the creatinine-cystatin C CKD-EPI equation provided the best performance, with small bias (median, 3.0; 95% confidence interval, 2.3 to 3.8) and higher precision (RMSE, 14.5) compared with creatinine-only or cystatin C-only equations (RMSE varying from 16.6 to 20), and this was also true in solid and hematological cancers. The creatinine-cystatin European Kidney Function Consortium equation had a similar performance to CKD-EPI, Cockcroft-Gault showed worst precision (30% of people with errors above 30%), and cystatin C CKD-EPI equation was the most biased, prone to underestimation of mGFR.ConclusionsIn our cohort of patients with mGFR and cancer, the CKD-EPI creatinine-cystatin C equation performed best for GFR assessment, and this was true for both solid and hematological cancers. Our findings give support for the preferential use of creatinine and cystatin C-based equations instead of creatinine-only or cystatin C-only equations in people with cancer.

Background: Glomerular filtration rate (GFR) assessment is important in clinical practice, with implications for diagnosis, prognostication, and drug dosing. People with cancer are at risk of imprecision in GFR estimation. This cross-sectional study evaluated the performance of various creatinine and cystatin C-based equations in comparison to measured GFR (mGFR) in people with cancer. Methods: We retrieved data for all adult patients who had mGFR by urinary iothalamate clearance between 2011 and 2023 at Mayo Clinic and use of an electronic health record diagnosis code for cancer within two years prior to mGFR. The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), European Kidney Function Consortium (EKFC), and Cockcroft-Gault (CG) equations were computed, along with performance metrics (bias, precision, and root mean square error, RMSE). Confidence intervals were generated by bootstrapping and analysis were stratified by solid and hematological cancer. Results: From all adults with cancer and mGFR, 1145 had both creatinine and cystatin C available within seven days of mGFR. Among all equations, the creatinine- cystatin C CKDEPI equation provided the best performance, with small bias (median 3.0, 95%CI 2.3-3.8) and higher precision (RMSE 14.5) compared to creatinine-only or cystatin-only equations (RMSE varying from 16.6 to 20), and this was also true in solid and hematological cancers. The creatinine-cystatin EKFC equation had a similar performance to CKDEPI, CG showed worst precision (30% of people with errors above 30%), and cystatin C CKDEPI equation was the most biased, prone to underestimation of mGFR. Conclusions: In our cohort of patients with mGFR and cancer, the CKDEPI creatinine-cystatin C equation performed best for GFR assessment, and this was true for both solid and hematological cancers. Our findings give support for the preferential use of creatinine and cystatin C-based equations instead of creatinine-only or cystatin C-only equations in people with cancer.

BACKGROUND:Cardiovascular guidelines have long recommended low-density lipoprotein-cholesterol (LDL-C) as the primary target for lipid-lowering therapy. Recent guidelines have emphasized the importance of achieving low LDL-C levels; hence, the accurate measurement of low LDL-C is increasingly clinically relevant. METHODS:Using lipid panel test results from the Mayo Clinic (n = 24 590) and the FOURIER clinical trial of evolocumab (n = 9605), the following modified Sampson equation was developed by least-squares regression to match LDL-C (mg/dL) by the β-quantification reference method, by combining terms into non High Density Lipoprotein Cholesterol (nonHDLC = Total Cholesterol - High Density Lipoprotein Cholesterol) and forcing the coefficient to be one. RESULTS:The modified Sampson equation demonstrated significant improvement in its concordance to the reference method compared to other equations (the Lin Concordance Correlation Coefficient 0.992, P < 0.001). By overall kappa analysis, it showed the best agreement to the reference method at the 55 mg/dL cutpoint (1.4 mmol/L, 0.98 [P < 0.001], Sampson-NIH: 0.96, Martin-Hopkins: 0.96, Friedewald: 0.94) and the 70 mg/dL cutpoint (1.8 mmol/L, 0.97 [P < 0.001], Sampson-NIH: 0.94, Martin-Hopkins: 0.95, Friedewald: 0.92). The false classification rate of the modified Sampson equation was also significantly lower compared to the other equations at 55 mg/dL (15%, [P < 0.001], Sampson-NIH: 29%, Martin-Hopkins: 28%, Friedewald: 37%) and 70 mg/dL (18%, [P < 0.001]; Sampson-NIH: 30%, Martin-Hopkins: 28.%, Friedewald: 34%). The new equation increases the percentage of correctly classified patients with low LDL-C by approximately 10% to 20% over the other equations based on its net reclassification index. CONCLUSIONS:The modified Sampson equation shows improved accuracy compared to other equations for low LDL-C. It more accurately identifies high-risk patients, who are not at their LDL-C goals and could benefit from more intensive lipid-lowering therapy.

Ceramides (Cer) are sphingolipids that can accumulate in human blood plasma during metabolic disorders, insulin resistance, and diabetes. Monitoring levels of four circulating plasma ceramides─Cer 18:1;O2/16:0, Cer 18:1;O2/18:0, Cer 18:1;O2/24:0, and Cer 18:1;O2/24:1─can predict the risk for cardiovascular disease (CVD) events and death. Here, using a RapidFire instrument, we present an online Solid Phase Extraction-Tandem Mass Spectrometry (SPE-MS/MS) methodology for ultrafast (∼15 s/sample) measurements of these ceramides in human plasma. The addition of authentic deuterated standards enables absolute quantitation of each ceramide species, and linear calibration lines were obtained for all analytes in the biological and clinical range. The aim of this study was also to determine whether the results produced with the RapidFire-MS/MS platform are in agreement with an existing validated LC-MS/MS method currently used in the clinic. The applicability of the novel methodology was demonstrated by determining ceramide concentrations using both analytical methods in various biological samples, including mouse plasma, NIST reference materials, a human cohort of 99 individuals, and by performing a multicenter comparison. In all of these cases, the RapidFire-MS/MS method yielded results that were in agreement with the validated LC-MS/MS determination, addressing the need for increased speed of lipid analyses and facilitating the measurement of ceramides in large human cohorts for research and clinical applications.

In the original publication [...].

Objectives: The aims of this study were to (1) establish the maximum allowable interference limits for hemolysis, lipemia, and icterus for chemistry analytes tested in body fluid samples and (2) assess the effectiveness of serial dilution to mitigate spectral interferences. Methods: Residual body fluids from clinically ordered testing were mixed (<10% by volume) with stock solutions of interferent (spiked) and compared with a control spiked with an equal volume of 0.9% saline. The analytes were measured on the Roche cobas c501 instrument. Difference and percentage difference were calculated and compared with allowable total error limits. A subset of samples were serially diluted with 0.9% saline. Mean (SD) difference and percentage difference were calculated. Results: The interference thresholds were lower than the package insert for lactate dehydrogenase, cholesterol, triglycerides, and total protein for hemolysis; amylase, cholesterol, and total protein for icterus; and albumin for lipemia. Only cholesterol and triglyceride results returned to baseline upon dilution of icteric samples. Conclusions: Interference thresholds in body fluids were lower than blood for 6 analytes. Diluting interferences that surpass these limits does not produce reliable results that are comparable to the baseline results before spiking in the interferent.

Background Clinical risk scores are used to identify those at high risk of atherosclerotic cardiovascular disease (ASCVD). Despite preventative efforts, residual risk remains for many individuals. Very low‐density lipoprotein cholesterol (VLDL‐C) and lipid discordance could be contributors to the residual risk of ASCVD. Methods and Results Cardiovascular disease–free residents, aged ≥40 years, living in Olmsted County, Minnesota, were identified through the Rochester Epidemiology Project. Low‐density lipoprotein cholesterol (LDL‐C) and VLDL‐C were estimated from clinically ordered lipid panels using the Sampson equation. Participants were categorized into concordant and discordant lipid pairings based on clinical cut points. Rates of incident ASCVD, including percutaneous coronary intervention, coronary artery bypass grafting, stroke, or myocardial infarction, were calculated during follow‐up. The association of LDL‐C and VLDL‐C with ASCVD was assessed using Cox proportional hazards regression. Interaction between LDL‐C and VLDL‐C was assessed. The study population (n=39 098) was primarily White race (94%) and female sex (57%), with a mean age of 54 years. VLDL‐C (per 10‐mg/dL increase) was significantly associated with an increased risk of incident ASCVD (hazard ratio, 1.07 [95% CI, 1.05–1.09]; P <0.001]) after adjustment for traditional risk factors. The interaction between LDL‐C and VLDL‐C was not statistically significant ( P =0.11). Discordant individuals with high VLDL‐C and low LDL‐C experienced the highest rate of incident ASCVD events, 16.9 per 1000 person‐years, during follow‐up. Conclusions VLDL‐C and lipid discordance are associated with a greater risk of ASCVD and can be estimated from clinically ordered lipid panels to improve ASCVD risk assessment.

Introduction: Biomarkers can facilitate the prediction of events in primary prevention. Few studies have been conducted in the community setting with analyses that incorporate many biomarkers. Hypothesis: We tested whether a multi biomarker model would outperform clinical factors and individual biomarkers for predicting MACE and Stroke/MI in subjects without known CAD. Methods: A retrospective cohort study assessed composite outcomes MACE (MI, CABG, PCI, stroke, and death) and Stroke/MI. Cox proportional hazard models were fit for individual biomarkers, adjusted for age, gender, BMI, hypertension, CAD, and GFR. Multi biomarker models were developed based on AIC values from the single-biomarker models. Bootstrap tests compared survival C-statistics and relative Integrated Discrimination Index (IDI). Results: 1131 patients in Olmsted County, MN were studied. Median age was 63.1 years, 97.5% were Caucasian, and 52.2% were female. Median BMI was 27.8. Kaplan Meier rates of MACE and Stroke/MI were 29.2% (CI = 26.5-31.8%) and 12.3% (CI = 10.3% - 14.3%), at 10 years. Adjusted NT proBNP models showed a 31% increased risk of MACE/death (HR = 1.31; CI = 1.17-1.46) and a 31% increased risk for stroke/MI (HR = 1.31; CI = 1.08-1.58). Adjusted Ceramide score models showed a 13% increased risk of MACE/death (HR = 1.13; CI = 1.04-1.24) and a 29% increased risk for stroke/MI (HR = 1.29; CI = 1.11-1.51). NT proBNP and the Ceramide score with clinical factors was better than clinical factors alone for MACE/Death (Relative IDI = 29.7%; p = 0.003) and Stroke/MI (Relative IDI = 36.1%; p = 0.034). This combined model did not outperform the strongest single biomarker model for Stroke/MI or MACE/Death. Other biomarkers were not significant when added to the combined model. Discussion: Ceramide score and NT proBNP alone and together improve the prediction of MACE and Stroke/MI in a community primary prevention cohort.

Background The accurate measurement of blood lipids and lipoproteins is crucial for the clinical management of atherosclerotic disease risk. Despite progress in standardization, there are still significant variations in pre-analytical requirements, methods, nomenclature, and reporting work flows.Content The guidance document aims to improve standardization of clinical lipid testing work flows. It provides recommendations for the components of the lipid panel, fasting requirements, reporting of results, and specific recommendations for non-high-density lipoprotein cholesterol (non-HDL-C), low-density lipoprotein cholesterol (LDL-C), lipoprotein(a) [Lp(a)], apolipoprotein B (apo B), point-of-care lipid testing, and LDL subfraction testing.Summary Lipid panels should always report non-HDL-C and LDL-C calculations if possible. Fasting is not routinely required except in specific cases. Modern equations should be utilized for LDL-C calculation. These equations allow for LDL-C reporting at elevated concentrations of triglycerides and obviate the need for direct measured LDL-C in most cases.