Immunofluorometric Point-of-Care Assays for the Detection of Acute Coronary Syndrome-Related Noncomplexed Pregnancy-Associated Plasma Protein A

Exploring free pregnancy associated plasma protein a (fPAPP-A) as a biomarker in early pregnancy

Objectives

In combined first trimester screening for Down syndrome, Pregnancy-Associated Plasma Protein A (PAPP-A) is pivotal. PAPP-A tests evaluate total PAPP-A, consisting of the biologically active free PAPP-A (fPAPP-A) and PAPP-A complexed with eosinophil major basic protein's proform (proMBP). While PAPP-A is well-researched, limited understanding persists regarding fPAPP-A's first trimester concentrations and diagnostic utility.

Design

and methods: PAPP-A and fPAPP-A levels were gauged in 602 serum samples at 2-week intervals (gestational weeks 4-14) from 159 women with delivery of a healthy neonate and 80 samples from 37 miscarriages. The final sample at the time of diagnosis from women who miscarried was included in analyses.

Results

During the first trimester, PAPP-A and fPAPP-A levels displayed significant and strong correlation (r = 0.94), with median values doubling weekly. Free PAPP-A constituted only 3.0 % of PAPP-A over gestational weeks. Low fPAPP-A linked to miscarriage (p < 0.001), maternal weight (p < 0.001), and smoking (p = 0.02). For miscarriage prediction fPAPP-A was equal to PAPP-A (area under the receiver operating characteristics curve 0.79 vs. 0.81, p = 0.44).

Conclusions

Investigating fPAPP-A presence and concentration directly in first trimester serum has not been done previously. This study report lower fPAPP-A values than anticipated from prior enzymatic studies of fPAPP-A. fPAPP-A was not superior to PAPP-A as a first trimester biomarker in this dataset.

Effect of Anthocyanins Supplementation on Serum IGFBP-4 Fragments and Glycemic Control in Patients with Fasting Hyperglycemia: A Randomized Controlled Trial

BACKGROUND

Insulin-like growth factor binding protein-4 (IGFBP-4) fragments have been shown to be associated with cardiometabolic diseases. Anthocyanins as a subgroup of natural polyphenols could have benefits on treating cardiometabolic diseases. The aim of this study was to examine the effects of purified anthocyanins on serum IGFBP-4 fragments and glycemic control in patients with fasting hyperglycemia.

METHODS

A set of 121 participants with elevated fasting glucose (≥5.6 mmol/L), who were originally randomly assigned to anthocyanins (320 mg/day) or placebo groups, were included in this study. Serum IGFBP-4 fragments, fasting and postload glucose, insulin, and C-peptide after a three-hour oral glucose tolerance test (OGTT) were measured at baseline and at the end of 12 weeks.

RESULTS

Compared with placebo, anthocyanins increased serum IGFBP-4 fragments (net change 8.33 ng/mL, 95% CI [1.2, 15.47], p=0.023) and decreased fasting glucose (-0.4 mmol/L [-0.71, -0.1], p=0.01), 2-hour C-peptide (-1.02 ng/mL [-1.99, -0.04], p=0.041) and the 3-hour area under the curve (AUC) of C-peptide (-2.19 [-4.11, -0.27], p=0.026). No other significant difference in parameters for glycemic control and insulin resistance was observed.

CONCLUSION

Anthocyanins supplementation for 12 weeks improved serum IGFBP-4 fragments and decreased fasting glucose and postload C-peptide in patients with fasting hyperglycemia. Further studies are needed to confirm our findings and clarify the potential mechanism.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02689765. Registered on 6 February 2016, https://clinicaltrials.gov/ct2/show/NCT02689765.

Direct Immunoassay for Free Pregnancy-Associated Plasma Protein A (PAPP-A)

Background

Pregnancy-associated plasma protein A (PAPP-A), especially in its noncomplexed form (fPAPP-A), is linked to vulnerable atherosclerotic plaques and risk of cardiac events. An assay for sensitive detection of fPAPP-A has been lacking. Our aim was to develop and validate a direct fPAPP-A assay to meet this need.

Methods

Monoclonal antibodies binding exclusively fPAPP-A were produced by immunizing mice with recombinant PAPP-A. In the optimized immunoassay, we used an fPAPP-A–specific capture antibody together with a lanthanide-chelate–labeled monoclonal antibody recognizing all PAPP-A forms. The assay was evaluated with CLSI guidelines and compared to a 2-assay subtractive fPAPP-A approach. Clinical performance was assessed with acute coronary syndrome patients.

Results

The limits of detection and quantitation were 0.4 mIU/L and 1.3 mIU/L, respectively, and the assay was linear up to 1000 mIU/L (R2 = 0.999). Both serum and heparin plasma were suitable matrices, and the complexed form of PAPP-A caused no significant interference. Correlation between the developed assay and the 2-assay approach was fair (Pearson's r = 0.819). Median concentration in healthy individuals was 1.0 mIU/L. fPAPP-A concentration was higher in patients who had myocardial infarction or died during the 1-year follow-up period than in those who did not (1.13 mIU/L vs 0.82 mIU/L, P = 0.008, model adjusted with age and sex). fPAPP-A measured with this direct assay predicted this end point as well as (follow-up 1 year) or better (30 days) than the 2-assay fPAPP-A alone or in combination with cTnI.

Conclusions

The new assay enables sensitive and reliable measurement of low cardiac-related fPAPP-A concentrations from blood samples.

IGFBP-4 and PAPP-A in normal physiology and disease

Insulin-like growth factor (IGF) binding protein-4 (IGFBP-4) is a modulator of the IGF system, exerting both inhibitory and stimulatory effects on IGF-induced cellular growth. IGFBP-4 is the principal substrate for the enzyme pregnancy-associated plasma protein-A (PAPP-A). Through IGF-dependent cleavage of IGFBP-4 in the vicinity of the IGF receptor, PAPP-A is able to increase IGF bioavailability and stimulate IGF-mediated growth. Recently, the stanniocalcins (STCs) were identified as novel inhibitors of PAPP-A proteolytic activity, hereby adding additional members to the seemingly endless list of proteins belonging to the IGF family. Our understanding of these proteins has advanced throughout recent years, and there is evidence to suggest that the role of IGFBP-4 and PAPP-A in defining the relationship between total IGF and IGF bioactivity can be linked to a number of pathological conditions. This review provides an overview of the experimental and clinical findings on the IGFBP-4/PAPP-A/STC axis as a regulator of IGF activity and examines the conundrum surrounding extrapolation of circulating concentrations to tissue action of these proteins. The primary focus will be on the biological significance of IGFBP-4 and PAPP-A in normal physiology and in pathophysiology with emphasis on metabolic disorders, cardiovascular diseases, and cancer. Finally, the review assesses current new trajectories of IGFBP-4 and PAPP-A research.

Pregnancy associated plasma protein-A as a prognostic biomarker of all-cause mortality and cardiovascular events in patients presenting with chest pain: a systematic review

AIM

Novel biomarkers have been proposed for identification of patients at greater risk of future adverse events among those presenting with chest pain. In this review, we aim to elucidate the ability of pregnancy associated plasma protein-A (PAPP-A) to predict mortality and other cardiovascular events in this patient population.

METHODS

A literature search of the electronic databases Medline, Scopus, Cochrane Library and ClinicalTrials.gov was performed in order to identify studies investigating the utility of PAPP-A to predict mortality and adverse cardiovascular events in patients with chest pain.

RESULTS

Eight studies met our inclusion criteria. Five of these studies pertained to patients with confirmed ischemic chest pain, while the rest included patients presenting with chest pain possibly due to acute coronary syndrome, irrespectively of the underlying cause. Although the results for long-term events were inconclusive in both groups of patients, higher PAPP-A concentrations were found to be a significant predictor of short-term adverse events in patients with confirmed ischemic chest pain.

CONCLUSIONS

PAPP-A appears to be a potentially useful biomarker for short-term risk stratification of patients presenting with chest pain of ischemic origin. However, there is an eminent need for more standardized clinical studies investigating the prognostic value of this biomarker.

Design of Novel, Water Soluble and Highly Luminescent Europium Labels with Potential to Enhance Immunoassay Sensitivities

To meet the continual demands of more-sensitive immunoassays, the synthesis of novel luminescent Eu(III) chelate labels having similar substituted 4-(phenylethynyl)pyridine chromophores in three different chelate structure classes are reported. Significantly enhanced luminescence intensities were obtained, evidently caused by the intra-ligand charge transfer (ILCT) mediated sensitization, but the alternative ligands triplet state process cannot be ruled out. Based on the present study, even quite small changes on the chelate structure, and, especially, on the substituents' donor/acceptor strength on both ends of 4-(phenylethynyl)pyridine subunits have an unpredictable effect on the luminescence. The highest observed brightness was 16,400 M^-1cm^-1 in solution and 69,500 M^-1cm^-1 on dry surface, being 3.4 and 8.7 fold higher compared to the reference chelate. The new label chelates provide solutions for improved assay sensitivity up-to tenfold from the present concepts.

Potentially pathogenic circulating autoantibodies to cardiac troponin are present in hemodialysis patients

INTRODUCTION

Repetitive dialysis-induced cardiac injury is associated with elevated troponin levels, inflammation, and longitudinal reduction in cardiac function. Pathogenic autoantibodies to cardiac troponins (cTnAAb) produce inflammatory cardiomyopathy in murine models. This study aimed to explore the possibility that analogous autoimmune processes might occur in hemodialysis (HD) patients, by initially investigating cTnAAb prevalence, and exploring potential links with HD-induced myocardial stunning.

METHODS

In 130 prevalent HD patients from two centers (Derby, UK; Turku, Finland), cTnAAb (immunoassay) and cardiac troponins were quantified. Sixty-four patients underwent serial echocardiography to assess myocardial stunning.

FINDINGS

cTnAAb were present in 7% of patients. Dual positivity to cTnAAb and elevated cTn occurred in 3% and 6% for cTnI and cTnT, respectively. Patients with cTnAAb had significantly longer dialysis vintage (82 vs. 30 months, P = 0.024), higher cTnT (0.1 vs. 0.05 pg/mL, P = 0.04), cTnI (0.02 vs. 0.01 pg/mL, P = 0.029), and free PAPP-A (6.4 vs. 3.3 mIU/L, P = 0.038).

DISCUSSION

This is the first description of cTnAAb in HD patients, which raises the possibility that longitudinal exposure to repetitive HD-induced cardiac injury may lead to further autoimmune-based myocardial insult.

Pregnancy-associated plasma protein-A and the vulnerable plaque

For more than a decade, pregnancy-associated plasma protein-A (PAPP-A) has been examined for its relation to acute coronary syndrome (ACS) and the vulnerable plaque. This review summarizes the current knowledge of plasma PAPP-A in relation to nonpregnant individuals focusing on patients with ACS, discusses its use as a possible biomarker for diagnosis and prognosis in ACS, briefly describes the challenges in different assay technologies and describes the effect of heparin administration on PAPP-A concentrations in plasma.

Characterization of endogenously circulating IGFBP-4 fragments-Novel biomarkers for cardiac risk assessment

BACKGROUND

Recent findings show that circulating N- and C-terminal fragments of IGF-binding protein-4 (NT-IGFBP-4 and CT-IGFBP-4) can be utilized as biomarkers for cardiac risk assessment in acute coronary syndrome (ACS) patients. The fragments are thought to be the products of pregnancy-associated plasma protein A (PAPP-A)-dependent proteolysis. Two immunoassays for the measurement of IGFBP-4 fragments have been proposed. However, properties of the endogenous IGFBP-4 fragments that could influence the performance of the immunoassays were still not investigated.

METHODS

NT- and CT-IGFBP-4 were extracted from pooled ACS plasma using affinity purification, and their concentrations were measured using sandwich immunoassays utilizing antibodies specific to their proteolytic neo-epitopes or internal epitopes. The extracted fragments were characterized by Western blots (WB) and mass-spectrometry. ACS plasma samples were analyzed by size exclusion chromatography (SEC).

RESULTS

Immunoassays utilizing the neo-epitope-specific and the internal epitope-specific antibodies measured equal concentrations of the analyte in the endogenous IGFBP-4 fragments preparations. Only the 18 kDa NT-IGFBP-4 and 14 kDa CT-IGFBP-4 were detected in the WB analysis. Using mass-spectrometry, peaks corresponding to intact non-truncated and non-modified NT-IGFBP-4 (14626 Da) and CT-IGFBP-4 (11346 Da) were observed. The absence of complexed forms of IGFBP-4 in patients' plasma was demonstrated using SEC.

CONCLUSIONS

Endogenous NT- and CT-IGFBP-4 from ACS patients' plasma correspond to the PAPP-A-derived IGFBP-4 fragments and do not undergo any truncation, modification, or complex formation in the patients' blood. Because of the demonstrated intact state of the circulating IGFBP-4 fragments, the neo-epitope-specific immunoassays perform reliably, allowing further clinical validation of these novel biomarkers.

Elevated serum free pregnancy-associated plasma protein-A independently predicts mortality in haemodialysis patients but is not associated with recurrent haemodialysis-induced ischaemic myocardial injury

BACKGROUND/AIMS

Pregnancy-associated plasma protein-A (PAPP-A) is a putative marker of atheroma instability and ischaemic myocardial stress prior to necrosis. Total PAPP-A (tPAPP-A) levels in acute coronary syndromes predict adverse outcomes. However, free PAPP-A (fPAPP-A) predominates in the circulation. Ischaemic haemodialysis (HD)-induced cardiac injury (myocardial stunning) is common and is associated with markers of myocardial necrosis, inflammation, cardiovascular events and mortality. Coronary plaque instability in pathophysiology of HD-induced myocardial stunning has not been studied. We aimed to investigate the relationship of fPAPP-A with stunning and mortality.

METHODS

130 prevalent patients from two HD centres (Finland and UK) were studied. Pre-HD free, complexed and total PAPP-A were measured by immunoassay. A subset of 62 patients underwent echocardiography to assess HD-induced myocardial stunning. The mean duration of follow-up was 407 ± 98 days.

RESULTS

fPAPP-A was elevated (median: 3.45 mIU/l) and correlated with dialysis vintage (r = 0.391, p < 0.001), cardiac troponin T (cTnT; r = 0.29, p = 0.001) and cardiac troponin I (cTnI; r = 0.22, p = 0.01). PAPP-A was not related to stunning. Dialysis vintage and cTnT independently predicted Ln fPAPP-A (model R = 0.463). fPAPP-A, cTnT and age independently predicted death (Nagelkerke R(2) = 0.362).

CONCLUSIONS

fPAPP-A, a novel predictor of HD-related mortality, demonstrates better prognostic power than tPAPP-A. Coronary plaque instability may contribute to sub-lethal myocardial injury, but may not be critical in pathogenesis of HD-induced ischaemic cardiac injury.

N-terminal and C-terminal fragments of IGFBP-4 as novel biomarkers for short-term risk assessment of major adverse cardiac events in patients presenting with ischemia

OBJECTIVES

Pregnancy Associated Plasma Protein A (PAPP-A)-derived N- and C-terminal fragments of IGF-binding protein-4 (NT- and CT-IGFBP-4) released from vulnerable atherosclerotic plaques are proposed to be used for cardiovascular risk assessment.

DESIGN AND METHODS

NT- and CT-IGFBP-4 were measured by novel immunoassays in EDTA-plasma of 180 patients admitted to the emergency department with symptoms of myocardial ischemia but without ST-segment elevation. Six-month incidence of major adverse cardiac events (MACE), including myocardial infarction, cardiac death, percutaneous coronary interventions, and coronary artery bypass grafting was recorded.

RESULTS

Sixteen patients met the endpoint. NT- and CT-IGFBP-4 were strong predictors of MACE: area under ROC curve (AUC) 0.856 and 0.809, respectively. NT-IGFBP-4 concentrations≥214μg/L and CT-IGFBP-4 concentrations≥124μg/L were associated with increased risk of future MACE: adjusted hazard ratio 13.79 and 7.93, respectively.

CONCLUSIONS

IGFBP-4 fragments can be utilized as biomarkers for MACE prediction in patients with suspected myocardial ischemia.

A high-affinity recombinant antibody permits rapid and sensitive direct detection of myeloperoxidase

Over the past 10 years, a growing field of research supporting the value of myeloperoxidase (MPO) as a prognostic indicator in acute cardiac pathophysiologies has emerged. The availability of a rapid and disposable MPO detection platform would enable research clinicians to more readily assess MPO indications for guiding therapy and also facilitate clinicians at the patient interface to readily adopt MPO testing and potentially drive more informed prognoses. Here we describe the isolation of a high-affinity avian MPO-specific recombinant antibody panel using phage display. Rapid isolation of a suitable single-chain variable fragment (scFv) antibody was facilitated using a surface plasmon resonance (SPR)-based "off-rate ranking" screening process. The selected scFv was then successfully incorporated into a rapid, simple, and sensitive one-step lateral flow immunoassay (LFIA) for the detection of MPO. This "one-step" feature of the developed assay was made possible by the scFv's strong affinity for MPO, obviating the need for sandwich signal enhancement steps. The assay's rapid performance was also further enhanced by exploiting the intrinsic enzymatic properties of MPO in its final detection. Use of the optimized LFIA facilitated the sensitive detection of MPO in MPO-depleted serum within clinically relevant reference ranges.

Free vs Total Pregnancy-Associated Plasma Protein A (PAPP-A) as a Predictor of 1-Year Outcome in Patients Presenting with Non–ST-Elevation Acute Coronary Syndrome

Background: The free fraction of pregnancy-associated plasma protein A (FPAPP-A) was found to be the PAPP-A form released to the circulation in acute coronary syndrome (ACS). We estimated the prognostic value of FPAPP-A vs total PAPP-A (TPAPP-A) concentrations in forecasting death and nonfatal myocardial infarction (combined endpoint) in patients with non–ST-elevation ACS.

Methods: We recruited 267 patients hospitalized for symptoms consistent with non–ST-elevation ACS and followed them for 12 months. FPAPP-A, TPAPP-A, C-reactive protein (CRP), and cardiac troponin I (cTnI) were measured at admission; cTnI was also measured at 6–12 h and 24 h. Because of the recently shown interaction between PAPP-A and heparin, we excluded patients treated with any heparin preparations before the admission blood sampling.

Results: During the follow-up, 57 (21.3%) patients met the endpoint (22 deaths and 35 nonfatal myocardial infarctions). According to FPAPP-A (&lt;1.27, 1.27–1.74, &gt;1.74 mIU/L) and TPAPP-A (&lt;1.98, 1.98–2.99, &gt;2.99 mIU/L) tertiles, this endpoint was met by 12 (13.5%), 18 (20.2%), 27 (30.3%) (P = 0.02), and 17 (19.1%), 17 (19.1%), 23 (25.8%) (P = 0.54) patients, respectively. After adjusting for age, sex, diabetes, previous myocardial infarction, and ischemic electrocardiogram (ECG) findings, FPAPP-A &gt;1.74 mIU/L [risk ratio (RR) 2.0; 95% CI 1.0–4.1, P = 0.053), increased cTnI, and CRP ≥2.0 mg/L were independent predictors of an endpoint. The prognostic performance of TPAPP-A was inferior to that of FPAPP-A.

Conclusions: FPAPP-A seems to be superior as a prognostic marker compared to TPAPP-A, giving independent and additive prognostic information when measured at the time of admission in patients hospitalized for non–ST-elevation ACS.

Leukocyte counts, myeloperoxidase, and pregnancy-associated plasma protein a as biomarkers for cardiovascular disease: towards a multi-biomarker approach

We evaluated leukocyte counts and levels of CRP, fibrinogen, MPO, and PAPP-A in patients with stable and unstable angina pectoris, acute myocardial infarction, and healthy controls. All biomarkers were analyzed again after 6 months. Leukocyte counts and concentrations of fibrinogen, CRP, MPO, and PAPP-A were significantly increased in patients with acute myocardial infarction. Leukocyte counts and concentrations of MPO were significantly increased in patients with unstable angina pectoris compared with controls. After 6 months, leukocyte counts and MPO concentrations were still increased in patients with acute myocardial infarction when compared to controls. Discriminant analysis showed that leukocyte counts, MPO, and PAPP-A concentrations classified study group designation for acute coronary events correctly in 83% of the cases. In conclusion, combined assessment of leukocyte counts, MPO, and PAPP-A was able to correctly classify acute coronary events, suggesting that this could be a promising panel for a multibiomarker approach to assess cardiovascular risk.

Pregnancy-associated plasma protein-A, a marker for outcome in patients suspected for acute coronary syndrome

OBJECTIVES

To examine if pregnancy-associated plasma protein-A (PAPP-A) in patients with chest pain, could identify patients at risk for death or myocardial infarction.

DESIGN AND METHODS

Patients admitted with chest pain and both normal ECG and normal biomarkers were evaluated by serial measurement of PAPP-A. Main outcome measures were mortality and non-fatal myocardial infarction.

RESULTS

Median age of patients included (415) was 67years and 43% were women. The risk of death or non-fatal myocardial infarction after 3 months was 15% in the highest quartile of circulating PAPP-A compared with 3% in the lowest quartile (relative risk 3.7, p<0.01). Corresponding numbers after 1 year were 24% and 10% (relative risk 2.4, p=0.01).

CONCLUSION

In patients admitted with chest pain and both normal ECG and normal biomarkers PAPP-A seems to be valuable for predicting patients at high risk of death or non-fatal myocardial infarction.

Intravenous administration of low molecular weight and unfractionated heparin elicits a rapid increase in serum pregnancy-associated plasma protein A

BACKGROUND

Pregnancy-associated plasma protein A (PAPP-A) has been suggested as a useful diagnostic and prognostic marker in acute coronary syndromes. Because low molecular weight heparin (LMWH) and unfractionated heparin (UFH) are commonly used in these cases, we analyzed the effects of intravenous administration of these heparins on serum PAPP-A concentrations.

METHODS

Serum concentrations of total and free PAPP-A were analyzed in 14 patients on chronic hemodialysis and in 10 coronary angiography patients. Ten of the dialysis patients received standard LMWH anticoagulation at the start of dialysis, and 4 were treated with a heparin-free method. Two of the patients on heparin-free hemodialysis received a reduced LMWH bolus 2 h after the start of dialysis. All angiography patients received UFH at the start of the procedure, and 1 patient received 2 extra boluses of UFH. Serum PAPP-A concentrations were analyzed before and during the dialysis session and during the coronary angiography examination.

RESULTS

A rapid increase in total PAPP-A (median, 25-fold) was seen in all patients within 5 min of administration for both LMWH and UFH boluses. This response was due to an increase in free PAPP-A in the serum. PAPP-A did not increase significantly in the patients who underwent heparin-free hemodialysis. Repeated heparin boluses induced a new PAPP-A release. In vitro addition of heparins to samples of whole blood did not increase PAPP-A concentrations.

CONCLUSIONS

Intravenous administration of heparin induces an intense and rapid increase in free PAPP-A in the serum. We recommend that this effect be considered when PAPP-A is assessed as a biomarker in acute coronary syndromes.

Lateral flow (immuno)assay: its strengths, weaknesses, opportunities and threats. A literature survey

Lateral flow (immuno)assays are currently used for qualitative, semiquantitative and to some extent quantitative monitoring in resource-poor or non-laboratory environments. Applications include tests on pathogens, drugs, hormones and metabolites in biomedical, phytosanitary, veterinary, feed/food and environmental settings. We describe principles of current formats, applications, limitations and perspectives for quantitative monitoring. We illustrate the potentials and limitations of analysis with lateral flow (immuno)assays using a literature survey and a SWOT analysis (acronym for "strengths, weaknesses, opportunities, threats"). Articles referred to in this survey were searched for on MEDLINE, Scopus and in references of reviewed papers. Search terms included "immunochromatography", "sol particle immunoassay", "lateral flow immunoassay" and "dipstick assay".

Pregnancy-associated plasma protein-A (PAPP-A) and cardiovascular risk

The search for markers to improve risk prediction for individuals at risk of developing serious cardiovascular events is ongoing. New markers of coronary artery disease progression have been identified in recent years, among which, circulating levels of pregnancy-associated plasma protein-A (PAPP-A) offer an interesting profile. PAPP-A may play a role in the development of atherosclerotic lesions and represent also a marker of atheromatous plaque instability and extent of cardiovascular disease. PAPP-A has been shown to be a marker of adverse outcome in both acute coronary syndrome and stable coronary disease patients. The present article reviews currently available evidence supporting a role for PAPP-A as a marker of cardiovascular risk and discusses some of the pitfalls that may limit its use in clinical practice.

Follicular fluid and serum levels of inhibin A and pregnancy-associated plasma protein A in patients undergoing IVF

OBJECTIVE

To elucidate transport of intrafollicular proteins Inhibin A and pregnancy-associated plasma protein A (PAPP-A) across the follicular fluid (FF)/blood barrier.

DESIGN

A retrospective study.

SETTING

IVF lab at a university hospital, academic, and industrial research labs.

PATIENT(S)

Fifty-five women undertook the IVF program.

INTERVENTION(S)

Follicular fluid aspirations and analysis, blood sample drawing, and serum analysis.

MAIN OUTCOME MEASURE(S)

Concentrations of Inhibin A, PAPP-A, and major serum proteins in FF and serum, total amount of PAPP-A, and Inhibin A in FF.

RESULT(S)

The FF/blood barrier permeability was calibrated using major serum proteins. The FF/serum ratio decreased with the molecular mass of proteins, and their FF and serum concentrations were well correlated. In contrast, concentrations of Inhibin A in paired serum and FF samples showed a weak correlation (r = 0.563), whereas serum and FF concentrations of PAPP-A were independent of each other. The total amount of Inhibin A in FF correlated well with concentrations of Inhibin A in paired serum samples (r = 0.858), whereas the correlation between the total amount of FF PAPP-A and PAPP-A serum concentrations remains poor (r = 0.215).

CONCLUSION(S)

These observations suggest that at the day of oocyte retrieval, FF is a major source of serum Inhibin A but not of serum PAPP-A.

Pregnancy-associated plasma protein A in non-cardiac conditions

OBJECTIVE

PAPP-A is a promising new marker in coronary heart disease. It is important to investigate its specificity in order to establish its clinical utility as a marker of coronary heart disease.

DESIGN AND METHODS

PAPP-A was measured within 24 h following hospital admission in 1448 consecutive patients admitted with diagnoses other than acute coronary syndromes.

RESULTS

PAPP-A was detectable (> or = 4.0 mIU/L) in 278 (19.2%) patients, among whom the mean level was 6.3 mIU/L (95% C.I., 6.1-6.5 mIU/L). The 95 and 99 percentiles for PAPP-A were 7.3 and 9.4 mIU/L, respectively. There was no difference in the mean PAPP-A of different diagnoses (p=0.33). None of the specific diagnoses known to influence established coronary markers appeared to influence the level of circulating PAPP-A.

CONCLUSION

PAPP-A is low in patients without known coronary heart disease. PAPP-A levels seem to be a potentially highly specific marker for heart disease.

Early detection of acute coronary syndromes and risk stratification by multimarker analysis

Cardiac troponin is the standard biomarker for the diagnosis of acute myocardial infarction (AMI) and risk stratification for short-term adverse cardiac events (death, AMI or need for revascularization). Unfortunately, the concentration of troponin in blood is normal in AMI patients who present early after the onset of symptoms. As such, there is active research being conducted in finding early markers of AMI and risk stratification. Despite years of testing dozens of candidates, no single test has had the necessary clinical sensitivity and specificity for this indication. Therefore, many researchers have advocated multimarker testing. There are two approaches that have been taken for discovering new markers. The proteomic approach involves focusing on the differences in the biochemical signatures between the tissues or biological fluids of normal compared with diseased individuals. Specific biochemical targets are not preselected. The pathophysiologic approach involves combining biomarkers that indicate a particular pathway or event known to be involved in the disease process. In both approaches, some bioinformatic algorithm will be necessary in order to combine the information provided by the individual tests. Representative approaches include the Multimarker Index™, classification and regression tree analysis and neural networks.

Measurement and clinical significance of circulating PAPP-A in ACS patients

BACKGROUND

The rupture of coronary atherosclerotic plaque and subsequent thrombus formation are major events underlying acute coronary syndromes (ACS). Pregnancy associated plasma protein A (PAPP-A), a biomarker of plaque rupture, has been studied in patients with ACS. This review aimed to provide an overview of clinical utility of PAPP-A in ACS patients and analytical issues adhering to immunological PAPP-A measurement.

METHODS

The literature relating to PAPP-A in ACS, the molecular structure and immunodetection of PAPP-A was reviewed. PubMed was used to search the relevant articles published from 1974 to 2006.

RESULTS

Higher PAPP-A concentrations have been found in patients with ACS than in patients with stable angina and subjects without coronary artery disease. Elevated PAPP-A concentrations have also been shown to associate with adverse cardiac events in ACS patients. The prognostic value of PAPP-A appears to be independent of cardiac troponins. Noteworthy, the PAPP-A form that accounts for increase in ACS is uncomplexed with the proform of eosinophil major basic protein (proMBP). However, PAPP-A assays applied in clinical studies published thus far detect total PAPP-A. Consequently, the clinical value may be non-optimal when total PAPP-A is measured in ACS patients. In addition, the clinical value can also be affected by the analytical factors that exert an effect on the performance of PAPP-A assays.

CONCLUSIONS

PAPP-A appears to be a very promising biomarker useful in the clinical management of ACS patients. However, more prospective and interventional studies with carefully established immunoassays are required to validate its clinical utility.