scholarly journals Discrepancy between Cardiac Troponin Assays Due to Endogenous Antibodies

2020 ◽  
Vol 66 (3) ◽  
pp. 445-454 ◽  
Author(s):  
Leo Lam ◽  
Lisa Aspin ◽  
Robert Campbell Heron ◽  
Leah Ha ◽  
Campbell Kyle
Keyword(s):  
Regression Analysis ◽  
Polyethylene Glycol ◽  
Cardiac Troponin ◽  
Protein A ◽  
Gel Filtration ◽  
Interquartile Range ◽  
Clinical Use ◽  
Gel Filtration Chromatography ◽  
Polyethylene Glycol Precipitation

Abstract Background Despite well-described analytical effects of autoantibodies against cardiac troponin (cTn) I on experimental assays, no study has systematically examined their impact on cTn assays in clinical use. We determined the effects of endogenous antibodies on 5 different cTnI assays and a cTnT assay. Methods cTn was measured by 6 methods: Siemens hs-cTnI Centaur, Siemens hs-cTnI Vista, Abbott hs-cTnI Architect, Beckman hs-cTnI Access, Beckman cTnI Access, and Roche hs-cTnT Elecsys. Measurements were repeated on 5 assays (all except Siemens hs-cTnI Vista) following immunoglobulin depletion by incubation with protein A. Low recovery of cTnI (<40%) following immunoglobulin depletion was considered positive for macro-cTnI. Protein A findings were validated by gel filtration chromatography and polyethylene glycol precipitation. Results In a sample of 223 specimens selected from a community laboratory that uses the Siemens hs-cTnI Centaur assay and from which cTn was requested, 76% of samples demonstrated increased cTnI (median, 88 ng/L; interquartile range, 62–204 ng/L). Macro-cTnI was observed in 123 (55%) of the 223 specimens. Comparisons of cTnI assays markedly improved once patients with macro-cTnI were removed. Passing-Bablok regression analysis between hs-cTnI assays demonstrated different slopes for patients with and without macro-cTnI. In patients with macro-cTnI, 89 (72%) showed no effect on the recovery of cTnT, whereas 34 (28%) had reduced recovery of cTnT. The proportion of results above the manufacturers' 99th percentile varied with the cTn assay and macro-cTnI status. Conclusion We suggest that the observed discrepancy between hs-cTnI assays may be attributed in part to the presence of macro-cTnI.

Screening for macroamylase in a community hospital.

1984 ◽  
Vol 30 (5) ◽  
pp. 741-742 ◽  
Author(s):  
C A Isham ◽  
N A Ridgeway ◽  
R Hedrick ◽  
J C Cate
Keyword(s):  
Polyethylene Glycol ◽  
Community Hospital ◽  
Serum Amylase ◽  
Gel Filtration ◽  
Screening Procedure ◽  
Gel Filtration Chromatography ◽  
Polyethylene Glycol Precipitation ◽  
Precipitation Test

Abstract We evaluated the polyethylene glycol precipitation test (Gastroenterology 83: 378-382, 1982), looking for macroamylase in the serum of 66 patients whose values for serum amylase were above normal. Three patients (4.5%) were identified by this method as having macroamylase , and this was confirmed by gel-filtration chromatography and electrophoresis. We find this to be the test of choice as a screening procedure for macroamylasemia because of its speed, simplicity, and apparent reliability. Diagnosis of macroamylasemia is important in preventing needless treatment and investigation for pancreatitis.

False-Positive AxSYM Cardiac Troponin I Results in a 53-Year-Old Woman

2002 ◽  
Vol 126 (5) ◽  
pp. 606-609
Author(s):  
Ronald J. Knoblock ◽  
Christopher M. Lehman ◽  
Ruth A. Smith ◽  
Fred S. Apple ◽  
William L. Roberts
Keyword(s):  
Polyethylene Glycol ◽  
Rheumatoid Factor ◽  
Cardiac Troponin ◽  
Troponin I ◽  
Protein A ◽  
Cardiac Troponin I ◽  
Heterophile Antibody ◽  
Clinically Significant ◽  
Polyethylene Glycol Precipitation ◽  
Number Of Classes

Abstract A number of classes of endogenous antibodies, including heterophile, rheumatoid factor, and autoantibodies, can interfere with immunoassay measurements of many different analytes. Heterophile and rheumatoid factor antibody interferences have been described previously for the AxSYM cardiac troponin I assay. Several commercial products have been developed to neutralize heterophile antibody interferences. We describe a patient with multiple apparently falsely elevated cardiac troponin I results that were unique to the AxSYM analyzer. These cardiac troponin I results diluted linearly. When treated with 2 different heterophile-blocking reagents, the magnitudes of the falsely elevated results increased 17- and 26-fold, and these results also demonstrated dilution linearity. This interfering substance could be removed by passage through an immobilized protein A column and by polyethylene glycol precipitation. It does not appear to be a classic heterophile antibody, nor is it a paraprotein. Laboratorians must remain constantly vigilant for immunoassay interferences that lead to clinically significant inaccurate results and must recognize that accepted methods for detecting and neutralizing the interference may be ineffective.

scholarly journals Specificity and Clinical Utility of Methods for the Detection of Macroprolactin

2006 ◽  
Vol 52 (7) ◽  
pp. 1366-1372 ◽  
Author(s):  
Lucille Kavanagh ◽  
T Joseph McKenna ◽  
Michael N Fahie-Wilson ◽  
James Gibney ◽  
Thomas P Smith
Keyword(s):  
Polyethylene Glycol ◽  
Clinical Utility ◽  
Protein A ◽  
Gel Filtration ◽  
Protein G ◽  
Serum Concentrations ◽  
Gel Filtration Chromatography ◽  
Common Cause ◽  
Choice Alternative ◽  
First Choice

Abstract Background: Increased serum concentrations of macroprolactin are a relatively common cause of misdiagnosis and mismanagement of hyperprolactinemic patients. Methods: We studied sera from a cohort of 42 patients whose biochemical hyperprolactinemia was explained entirely by macroprolactin. Using 5 pretreatments, polyethylene glycol (PEG), protein A (PA), protein G (PG), anti-human IgG (anti-hIgG), and ultrafiltration (UF), to deplete macroprolactin from sera before immunoassay, we compared residual prolactin concentrations with monomer concentrations obtained by gel-filtration chromatography (GFC). A monomeric prolactin standard was used to assess recovery and specificity of the pretreatment procedures. Results: Residual prolactin concentrations in all pretreated sera differed significantly (P <0.001) from monomeric concentrations obtained after GFC. PEG underestimated (mean, 75%), whereas PA, PG, anti-hIgG, and UF overestimated (means, 178%, 151%, 178%, and 112%, respectively) the amount of monomer present. Of the 5 methods examined, PEG correlated best with GFC (r = 0.80) followed by PG (r = 0.78), PA (r = 0.72), anti-hIgG (r = 0.70), and UF (r = 0.61). After UF or pretreatment with anti-hIgG or PEG, recovery of monomeric prolactin standard was low: 60%, 85%, and 77% respectively. In contrast, pretreatment with PA or PG gave almost quantitative recovery. Conclusions: None of the methods examined yielded results identical to the GFC method. PEG pretreatment yielded results that correlated best and is recommended as the first-choice alternative to GFC.

Macro-alkaline phosphatase due to IgG κ complex: demonstration with polyethylene glycol precipitation and immunofixation

2002 ◽  
Vol 39 (5) ◽  
pp. 523-525 ◽  
Author(s):  
MC Owen ◽  
LS Pike ◽  
PM George ◽  
ML Barclay ◽  
CM Florkowski
Keyword(s):  
Alkaline Phosphatase ◽  
Polyethylene Glycol ◽  
Gel Filtration ◽  
Light Chains ◽  
Elevated Plasma ◽  
Plasma Alkaline Phosphatase ◽  
Polyethylene Glycol Precipitation

An otherwise unexplained, persistently elevated plasma alkaline phosphatase concentration in a 71-year-old woman was found to be attributable to the presence of macro-alkaline phosphatase using polyethylene glycol precipitation. Gel filtration showed two high MW peaks with masses of about 330 kDa and 560 kDa. The alkaline phosphatase (ALP) complex was characterized by immunoelectrophoresis as a complex with IgG with κ light chains.

scholarly journals Frequency of Macroprolactinemia Due to Autoantibodies against Prolactin in Pregnant Women

2001 ◽  
Vol 86 (2) ◽  
pp. 924-929 ◽  
Author(s):  
Dalila Pascoe-Lira ◽  
Genoveva Duran-Reyes ◽  
Iris Contreras-Hernández ◽  
Leticia Manuel-Apolinar ◽  
Francisco Blanco-Favela ◽  
...  
Keyword(s):  
Polyethylene Glycol ◽  
Pregnant Women ◽  
Molecular Mass ◽  
Chromatographic Separation ◽  
Protein A ◽  
Gel Filtration ◽  
Serum Levels ◽  
The Other ◽  
Positive Correlation ◽  
Before And After

The frequency of macroprolactinemia related to the presence of anti-PRL autoantibodies in the serum of 209 healthy women at different stages of pregnancy was studied. Measurements were taken of serum PRL concentrations before and after chromatographic separation (gel filtration and affinity with proteins A and G) and extraction of free PRL with polyethylene glycol (PEG). Sera from 8 of the 209 women (3.8%) were found to have a significantly high proportion of precipitated PRL by PEG (macroprolactinemia); in these patients, gel filtration showed that a substantial amount of big big PRL (molecular mass >100 kDa) was present (19.0–78.2% vs. 3.8–4.9%, P = 0.009 in normal pregnant women with a normal proportion of precipitated PRL by PEG). The presence of macroprolactinemia was attributable to anti-PRL autoantibodies in 5 of the 8 women. Comparison of serum levels of direct and free PRL between women with macroprolactinemia related to anti-PRL autoantibodies and women without macroprolactinemia showed significant differences (direct PRL: 270.2 ± 86.9 vs. 203.4 ± 69.0 μg/L, P = 0.04; and free PRL: 107.0 ± 75.9 vs. 173.3 ± 67.6 μg/L, P = 0.002). On the other hand, there was no difference between women with macroprolactinemia not related to anti-PRL autoantibodies and women with macroprolactinemia caused by anti-PRL autoantibodies, nor was there a difference between women with macroprolactinemia not related to anti-PRL autoantibodies and women without macroprolactinemia. There was a positive correlation between titers of the anti-PRL autoantibody and serum PRL levels (r = 0.82, P = 0.09). The presence of the anti-PRL autoantibody had no relation to the patient’s age, stage of gestation, or number of previous pregnancies. We concluded that the frequency of macroprolactinemia was 3.8% among healthy, pregnant women, which was caused by a anti-PRL autoantibodies in 62.5% of the cases. The autoantibodies were found in the bloodstream, forming a PRL-IgG complex, in accordance with the following observations: 1) immunoreactive PRL on gel filtration was eluted in the fractions corresponding to the molecular mass of IgG (150 kDa); 2) a significantly high proportion of immunoreactive PRL was retained on an affinity gel for IgG (proteins A and G); and 3) a significantly high proportion of serum PRL bound to IgG was precipitated by protein A. There was a positive correlation between titers of anti-PRL autoantibodies and serum PRL levels. Serum levels of total PRL were higher, and serum levels of free PRL were lower, in pregnant women with anti-PRL autoantibodies than in pregnant women without macroprolactinemia.

A protein A-binding, polyethylene glycol precipitation-based immunoradiometric assay

1986 ◽  
Vol 89 (1) ◽  
pp. 27-35 ◽  
Author(s):  
L.C. Pontes-de-Carvalho ◽  
J. Lannes-Vieira ◽  
S. Giovanni-de-Simone ◽  
B. Galvão-Castro
Keyword(s):  
Polyethylene Glycol ◽  
Protein A ◽  
Immunoradiometric Assay ◽  
Polyethylene Glycol Precipitation

Macrocomplexes and discordant high-sensitivity cardiac troponin concentrations

2017 ◽  
Vol 55 (4) ◽  
pp. 500-504 ◽  
Author(s):  
Peter A Kavsak ◽  
Chantele Roy ◽  
Paul Malinowski ◽  
Ching-Tong Mark ◽  
Terry Scott ◽  
...  
Keyword(s):  
Polyethylene Glycol ◽  
Cardiac Troponin ◽  
Ethylenediaminetetraacetic Acid ◽  
High Sensitivity ◽  
Creatine Kinase Mb ◽  
Additional Testing ◽  
Analytical Range ◽  
Highly Correlated ◽  
Polyethylene Glycol Precipitation ◽  
Result Interpretation

Background Analytical comparisons between different high-sensitivity cardiac troponin (hs-cTn) assays are important for reassurance of results performed with different methodologies and to identify potential interferences or confounders to result interpretation. Our objective in the present study was to compare Beckman Coulter’s latest hs-cTnI assay to Abbott’s hs-cTnI assay and to assess agreement between results. Methods Two hundred ethylenediaminetetraacetic acid plasma samples that had clinically reported hs-cTnI results from the Abbott ARCHITECTi2000 that spanned the analytical range were stored (median = 4 h), re-centrifuged and retested for hs-cTnI on the Abbott ARCHITECTi1000 and Beckman Coulter Access2 analysers. Passing–Bablok regression and fold-differences were evaluated, with differences approximately three-fold between results further subjected to Roche hs-cTnT testing and polyethylene glycol precipitation. Results The Beckman and Abbott hs-cTnI concentrations were correlated ( r = 0.95) with Beckman yielding proportionally lower concentrations (slope = 0.78; 95%CI: 0.74–0.85). There were 12 samples that yielded Abbott hs-TnI concentrations ≥3-fold higher than the Beckman hs-cTnI concentrations; of which nine samples from seven different patients had sufficient quantity for additional testing. All seven patients had macrocomplexes as determined with polyethylene glycol precipitation that affected the Abbott hs-cTnI assay. One patient with Abbott hs-cTnI results >1300 ng/L had polyethylene glycol, heterophile antibodies and creatine kinase-MB testing performed which confirmed that a macrocomplex most likely affected the Abbott and Roche (hs-cTnT = 65 ng/L) assays but not the Beckman (hs-cTnI = 12 ng/L) assay. Conclusion The hs-cTnI concentrations obtained from ethylenediaminetetraacetic acid plasma between the Beckman and Abbott assays are highly correlated, with large differences in concentrations (≥3-fold) between Abbott and Beckman assays possible due to macrocomplexes.

scholarly journals Circulating Immunoreactive Cardiac Troponin Forms Determined by Gel Filtration Chromatography after Acute Myocardial Infarction

2010 ◽  
Vol 56 (6) ◽  
pp. 952-958 ◽  
Author(s):  
Katharine J Bates ◽  
Elizabeth M Hall ◽  
Michael N Fahie-Wilson ◽  
Heiko Kindler ◽  
Clare Bailey ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Acute Myocardial Infarction ◽  
Cardiac Troponin ◽  
Troponin I ◽  
Gel Filtration ◽  
High Molecular Mass ◽  
Gel Filtration Chromatography ◽  
Blood Samples ◽  
Mass Form ◽  
Time Point

Abstract Background: Cardiac troponin I (cTnI) and cTnT measurements are used in the diagnosis of acute myocardial infarction (AMI). Together with troponin C (TnC), the cTnI and cTnT forms make up the ternary cTnT-cTnI-TnC (TIC) complex found within myocardium. Whether cTn occurs in the circulation after AMI as ternary TIC, binary cTnI-TnC (IC) complexes, or free troponin forms has not been thoroughly investigated. Methods: Blood samples from 10 AMI patients were collected at hospital admission and then at 12, 24, and 48 h after onset of chest pain. Serum was subjected to gel filtration chromatography and cTnT (Roche cTnT) and cTnI (Siemens Centaur UltraTnI and Beckman Access AccuTnI) concentrations were measured in the gel filtration chromatography fractions. Results: cTnT was present predominantly as free cTnT and cTnI as binary IC complex. These 2 forms were present at every time point. Lesser quantities of TIC complex (6%–32% of total cTnT and <50% of total cTnI) were detected in 4 patients at varying times. Minor quantities of a high molecular mass form of cTnI were detected occasionally. No free cTnI was found. Both cTnI assays identified a similar pattern of cTnI forms. Conclusions: After AMI, cTnI is present in serum as TIC and IC complexes. cTnT may be present as a combination of TIC and free cTnT or exclusively as free cTnT.

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