Background β-Trace protein (BTP) and β2 -microglobulin (B2M) are novel glomerular filtration markers that have stronger associations with adverse outcomes than creatinine. Comparisons of BTP and B2M ...to creatinine and cystatin C are limited by the absence of rigorously developed glomerular filtration rate (GFR) estimating equations for the novel markers. Study Design Study of diagnostic test accuracy. Setting & Participants Pooled database of 3 populations with chronic kidney disease (CKD) with mean measured GFR of 48 mL/min/1.73 m2 (N = 3,551; MDRD Modification of Diet in Renal Disease Study, AASK African American Study of Kidney Disease and Hypertension, and CRIC Chronic Renal Insufficiency Cohort Study). Index Tests GFR estimated using creatinine, cystatin C, BTP, or B2M level. Reference Test GFR measured as the urinary clearance of iothalamate. Results For BTP and B2M, coefficients for age, sex, and race were smaller than for creatinine and were similar or smaller than for cystatin C. For B2M, coefficients for sex, age, and race were smaller than for creatinine and were similar (age and race) or smaller (sex) than for cystatin C. The final equations with BTP (BTP, age, and sex) or B2M (B2M alone) were less accurate than either the CKD-EPI (CKD Epidemiology Collaboration) creatinine or cystatin C equations. The combined BTP-B2M equation (BTP and B2M alone) had similar accuracy to the CKD-EPI creatinine or cystatin C equation. The average of the BTP-B2M equation and the CKD-EPI creatinine–cystatin C equation was not more accurate than the CKD-EPI creatinine–cystatin C equation. Limitations No external validation population, study population was restricted to CKD, few participants older than 65 years, or nonblack nonwhite race. Conclusions BTP and B2M are less influenced by age, sex, and race than creatinine and less influenced by race than cystatin C, but provide less accurate GFR estimates than the CKD-EPI creatinine and cystatin C equations. The CKD-EPI BTP and B2M equation provides a methodological advance for their study as filtration markers and in their associations with risk and adverse outcomes, but further study is required before clinical use.
Use of cystatin C for glomerular filtration rate estimation (eGFR) has garnered heightened interest as a means to avoid race-based medicine, since eGFRcys equations do not require specification of ...race. Before considering more widespread use of cystatin C, it is important to confirm that assays provide accurate measurements of cystatin C concentration, to ensure accurate GFR estimates.
To determine if the accuracy of cystatin C measurements in laboratories participating in the College of American Pathologists' (CAP) Cystatin C (CYS) survey has improved since 2014.
Two fresh frozen serum pools, the first from healthy donors without chronic kidney disease (CKD), and the second from patients with CKD, along with a synthetically prepared elevated cystatin C pool, were sent to laboratories participating in the 2019 CYS-A survey. Target values were established by using 2 immunoassays and a bracketed 2-point calibration with diluted ERM-DA471/IFCC reference material.
For the healthy donor fresh frozen pool (ERM-DA471/IFCC-traceable target of 0.725 mg/L), the all-method mean (standard deviation, coefficient of variation) was 0.731 mg/L (0.071, 9.7%). For the CKD pool (ERM-DA471/IFCC-traceable target of 2.136 mg/L), the all-method mean was 2.155 mg/L (0.182, 8.4%). For the synthetically spiked pool (ERM-DA471/IFCC-traceable target of 1.843 mg/L), the all-method mean was 1.886 mg/L (0.152, 8.1%). This represents marked improvement in accuracy and between-method agreement compared to the 2014 CAP survey.
Manufacturers have markedly improved accuracy and between-method agreement of cystatin C measurement procedures since 2014, which allows for greater confidence in estimated GFR relying on cystatin C.
Though the microbiome’s impact on immune system homeostasis is well documented, the effect of circulating T cells on the gut microbiome remains unexamined. We analyzed data from 50 healthy volunteers ...in a pilot trial of aspirin, using immunophenotyping and 16S rRNA sequencing to evaluate the effect of baseline T cells on microbiome changes over 6 weeks. We employed an unsupervised sparse canonical correlation analysis (sCCA) and used multivariable linear regression models to evaluate the association between selected T cell subsets and selected bacterial genera after adjusting for covariates. In the cross-sectional analysis, percentages of naïve CD4+ T cells were positively associated with a relative abundance of Intestinimonas, and the percentage of activated CD8+ T cells was inversely associated with Cellulosibacter. In the longitudinal analysis, the baseline percentages of naïve CD4+ T cells and activated CD4+ T cells were inversely associated with a 6-week change in the relative abundance of Clostridium_XlVb and Anaerovorax, respectively. The baseline percentage of terminal effector CD4+ T cells was positively associated with the change in Flavonifractor. Notably, the microbiome taxa associated with T cell subsets exclusively belonged to the Bacillota phylum. These findings can guide future experimental studies focusing on the role of T cells in impacting gut microbiome homeostasis.
Biotinylated antibodies and analogues, with their strong binding to streptavidin, are used in many clinical laboratory tests. Excess biotin in blood due to supplemental biotin ingestion may affect ...biotin-streptavidin binding, leading to potential clinical misinterpretation. However, the degree of interference remains undefined in healthy adults.
To assess performance of specific biotinylated immunoassays after 7 days of ingesting 10 mg/d of biotin, a dose common in over-the-counter supplements for healthy adults.
Nonrandomized crossover trial involving 6 healthy adults who were treated at an academic medical center research laboratory.
Administration of 10 mg/d of biotin supplementation for 7 days.
Analyte concentrations were compared with baseline (day 0) measures on the seventh day of biotin treatment and 7 days after treatment had stopped (day 14). The 11 analytes included 9 hormones (ie, thyroid-stimulating hormone, total thyroxine, total triiodothyronine, free thyroxine, free triiodothyronine, parathyroid hormone, prolactin, N-terminal pro-brain natriuretic peptide, 25-hydroxyvitamin D) and 2 nonhormones (prostate-specific antigen and ferritin). A total of 37 immunoassays for the 11 analytes were evaluated on 4 diagnostic systems, including 23 assays that incorporated biotin and streptavidin components and 14 assays that did not include biotin and streptavidin components and served as negative controls.
Among the 2 women and 4 men (mean age, 38 years range, 31-45 years) who took 10 mg/d of biotin for 7 days, biotin ingestion-associated interference was found in 9 of the 23 (39%) biotinylated assays compared with none of the 14 nonbiotinylated assays (P = .007). Results from 5 of 8 biotinylated (63%) competitive immunoassays tested falsely high and results from 4 out of 15 (27%) biotinylated sandwich immunoassays tested falsely low.
In this preliminary study of 6 healthy adult participants and 11 hormone and nonhormone analytes measured by 37 immunoassays, ingesting 10 mg/d of biotin for 1 week was associated with potentially clinically important assay interference in some but not all biotinylated assays studied. These findings should be considered for patients taking biotin supplements before ordering blood tests or when interpreting results.
clinicaltrials.gov Identifier: NCT03034707.
We assessed the feasibility of a highly sensitive immunoassay method based on single molecule array (Simoa) technology to detect IgG and IgA antibodies against SARS-CoV-2 spike protein receptor ...binding domain (RBD) in saliva from individuals with natural or vaccine-induced COVID-19 immunity. The performance of the method was compared to a laboratory-developed SARS-CoV-2 RBD total antibody enzyme-linked immunosorbent assay (ELISA). Paired serum and saliva specimens were collected from individuals (n = 40) prior to and 2 weeks after receiving an initial prime COVID-19 vaccine dose (Pfizer/BioNTech BNT162b2 or Moderna mRNA-1273). Saliva was collected using a commercially available collection device (OraSure Inc.) and SARS-CoV-2 RBD IgG antibodies were measured by an indirect ELISA using concentrated saliva samples and a Simoa immunoassay using unconcentrated saliva samples. The IgG results were compared with paired serum specimens that were analyzed for total RBD antibodies using the ELISA method. The analytical sensitivity of the saliva-based Simoa immunoassay was five orders of magnitude higher than the ELISA assay: 0.24 pg/mL compared to 15 ng/mL. The diagnostic sensitivity of the saliva ELISA method was 90% (95% CI 76.3-97.2%) compared to 91.7% (95% CI 77.5-98.2%) for the Simoa immunoassay without total IgG-normalization and 100% (95% CI 90.3-100%) for the Simoa immunoassay after total IgG-normalization when compared to the serum ELISA assay. When analyzed using the SARS-CoV-2 RBD IgG antibody ELISA, the average relative increase in antibody index (AI) between the saliva of the post- and pre-vaccinated individuals was 8.7 (AI
). An average relative increase of 431 pg/mL was observed when the unconcentrated saliva specimens were analyzed using the Simoa immunoassay (SARS-CoV-2 RBD IgG
). These findings support the suitability of concentrated saliva specimens for the measurement of SARS-CoV-2 RBD IgG antibodies via ELISA, and unconcentrated saliva specimens for the measurement of SARS-CoV-2 RBD IgG and IgA using an ultrasensitive Simoa immunoassay.
Background: Tubular biomarkers may provide insight into progression of kidney tubulointerstitial pathology that is complementary to traditional measures of glomerular function and damage.
Methods: We ...examined longitudinal tubular biomarker trajectories in the DCCT/EDIC Study of T1D. For each of 220 randomly-selected participants, biomarkers were measured at up to 7 time points over 26 years. Measurements comprised KIM-1 and sTNFR1 in plasma, EGF and MCP1 in timed urine, and a composite tubular secretion score calculated from the urinary clearances of 8 small molecules secreted by the proximal tubule. Biomarker trends were described and associations with intensive diabetes therapy and glycemia changes over time were tested.
Results: Mean age was 28 years at baseline, 45% were women, and 50% were assigned to intensive versus conventional therapy during DCCT. At baseline, participants had a mean estimated glomerular filtration rate (eGFR) of 125 ml/min/1.73m2, and 90% had a urinary albumin excretion rate (AER) < 30 mg/24h. Mean changes in biomarkers over time (in percent per decade) were: KIM-1 27.3% (95% CI 21.4, 33.5), sTNFR1 16.9% (95% CI 14.5, 19.3), MCP1 18.4% (95% CI 8.9, 28.8), EGF -13.5% (95% CI -16.7, -10.1), EGF/MCP1 -26.9% (95% CI -32.2, -21.3), and tubular secretion score -0.9% (95% CI -1.8, 0.0), compared with -12.0% (95% CI -12.9, -11.1) for eGFR and 10.9% (95% CI 2.5, 20.1) for AER. Intensive versus conventional therapy was associated with slower rise in sTNFR1 (relative difference in change 0.94; 95% CI 0.90, 0.98). Higher time-updated HbA1c was associated with faster rises in sTNFR1 (relative difference in change 1.06 per 1% higher HbA1c; 95% CI 1.05, 1.08) and KIM-1 (1.09; 95% CI 1.05, 1.14).
Conclusion: Among people with T1D and normal eGFR at baseline, kidney tubular biomarkers changed significantly over long-term follow-up. Hyperglycemia was associated with larger increases in plasma sTNFR1 and KIM1 over time.
Disclosure
C.Limonte: None. I.Bebu: None. J.Seegmiller: None. M.Molitch: Consultant; Amryt Pharma Plc, Corcept Therapeutics, Janssen Pharmaceuticals, Inc., Sention, Takeda Pharmaceutical Co., Ltd. B.A.Perkins: Advisory Panel; Dexcom, Inc., Insulet Corporation, Novo Nordisk, Sanofi, Vertex Pharmaceuticals Incorporated, Other Relationship; Abbott, Medtronic, Sanofi, Research Support; Novo Nordisk, Bank of Montreal (BMO). A.B.Karger: Consultant; Roche Diagnostics, Research Support; Kyowa Kirin Co., Ltd., Siemens, Speaker's Bureau; Siemens, American Society of Nephrology, American Kidney Fund, National Kidney Foundation. I.De boer: Advisory Panel; AstraZeneca, Boehringer Ingelheim and Eli Lilly Alliance, Boehringer Ingelheim International GmbH, Otsuka America Pharmaceutical, Inc., Bayer Inc., Consultant; George Clinical, Gilead Sciences, Inc., Medscape, Research Support; Dexcom, Inc. Dcct/edic writing group: n/a.
Funding
National Institute of Diabetes and Digestive and Kidney Diseases (U01DK094176, U01DK094157)
•Middleware design flaws can impact laboratory operations and patient care.•A results display design flaw led to missed sodium critical value alerts.•Labs should examine all aspects of middleware ...interfaces during validation.
In 2018, our clinical laboratory was alerted to back-to-back plasma sodium critical value callback failures on the same patient, occurring on different shifts and involving different technologists. Therefore, we set forth to investigate the root cause for the critical value callback failures.
We conducted a thorough investigation focused on the processes associated with critical value identification and notification for plasma sodium measurement performed on the Siemens Vista.
Our investigation uncovered a flaw in the Siemens CentraLink middleware software. A default dark blue bar in the top row of the results review display was determined to obscure the red color which highlights critical values for lab staff identification. Sodium was disproportionately impacted by this flaw, as it is commonly ordered as part of metabolic panels, and is listed first among the panel analytes in the top row of the CentraLink display. Retrospective data review comparing critical callback failure rates for sodium to potassium and hemoglobin confirmed that sodium had significantly higher critical callback failure rates than these other analytes. After alerting the product manufacturer, Siemens programmed the CentraLink display so that the top row was blank and devoid of patient results, so that the blue color in the top row would no longer obscure the red visual cue of a patient’s critical result. Sodium critical value callback failures were reduced to 0% after this middleware display correction.
Middleware design flaws can have unexpected consequences on clinical laboratory operations. We encourage clinical laboratories to closely examine user interfaces utilized by laboratory staff, and be wary of potential impacts that the display format may have on results reporting.
BACKGROUNDWe investigated residual β cell function in Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) study participants with an average ...35-year duration of type 1 diabetes mellitus (T1DM).METHODSSerum C-peptide was measured during a 4-hour mixed-meal tolerance test. Associations with metabolic outcomes and complications were explored among nonresponders (all C-peptide values after meal <0.003 nmol/L) and 3 categories of responders, classified by peak C-peptide concentration (nmol/L) as high (>0.2), intermediate (>0.03 to ≤0.2), and low (≥ 0.003 to ≤0.03).RESULTSOf the 944 participants, 117 (12.4%) were classified as responders. Residual C-peptide concentrations were associated with higher DCCT baseline concentrations of stimulated C-peptide (P value for trend = 0.0001). Residual C-peptide secretion was not associated with current or mean HbA1c, HLA high-risk haplotypes for T1DM, or the current presence of T1DM autoantibodies. The proportion of subjects with a history of severe hypoglycemia was lower with high (27%) and intermediate (48%) residual C-peptide concentrations than with low (74%) and no (70%) residual C-peptide concentrations (P value for trend = 0.0001). Responders and nonresponders demonstrated similar rates of advanced microvascular complications.CONCLUSIONβ Cell function can persist in long-duration T1DM. With a peak C-peptide concentration of >0.03 nmol/L, we observed clinically meaningful reductions in the prevalence of severe hypoglycemia.TRIAL REGISTRATIONClinicalTrials.gov NCT00360815 and NCT00360893.FUNDINGDivision of Diabetes Endocrinology and Metabolic Diseases of the National Institute of Diabetes and Digestive and Kidney Diseases (DP3-DK104438, U01 DK094176, and U01 DK094157).
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