High-resolution pediatric reference intervals for 15 biochemical analytes described using fractional polynomials

OBJECTIVES

Assessment of children's laboratory test results requires consideration of the extensive changes that occur during physiological development and result in pronounced sex- and age-specific dynamics in many biochemical analytes. Pediatric reference intervals have to account for these dynamics, but ethical and practical challenges limit the availability of appropriate pediatric reference intervals that cover children from birth to adulthood. We have therefore initiated the multi-center data-driven PEDREF project (Next-Generation Pediatric Reference Intervals) to create pediatric reference intervals using data from laboratory information systems.

METHODS

We analyzed laboratory test results from 638,683 patients (217,883-982,548 samples per analyte, a median of 603,745 test results per analyte, and 10,298,067 test results in total) performed during patient care in 13 German centers. Test results from children with repeat measurements were discarded, and we estimated the distribution of physiological test results using a validated statistical approach (kosmic).

RESULTS

We report continuous pediatric reference intervals and percentile charts for alanine transaminase, aspartate transaminase, lactate dehydrogenase, alkaline phosphatase, γ-glutamyl-transferase, total protein, albumin, creatinine, urea, sodium, potassium, calcium, chloride, anorganic phosphate, and magnesium. Reference intervals are provided as tables and fractional polynomial functions (i.e., mathematical equations) that can be integrated into laboratory information systems. Additionally, Z-scores and percentiles enable the normalization of test results by age and sex to facilitate their interpretation across age groups.

CONCLUSIONS

The provided reference intervals and percentile charts enable precise assessment of laboratory test results in children from birth to adulthood. Our findings highlight the pronounced dynamics in many biochemical analytes in neonates, which require particular consideration in reference intervals to support clinical decision making most effectively.

Next-generation reference intervals for pediatric hematology

Background Interpreting hematology analytes in children is challenging due to the extensive changes in hematopoiesis that accompany physiological development and lead to pronounced sex- and age-specific dynamics. Continuous percentile charts from birth to adulthood allow accurate consideration of these dynamics. However, the ethical and practical challenges unique to pediatric reference intervals have restricted the creation of such percentile charts, and limitations in current approaches to laboratory test result displays restrict their use when guiding clinical decisions. Methods We employed an improved data-driven approach to create percentile charts from laboratory data collected during patient care in 10 German centers (9,576,910 samples from 358,292 patients, 412,905-1,278,987 samples per analyte). We demonstrate visualization of hematology test results using percentile charts and z-scores (www.pedref.org/hematology) and assess the potential of percentiles and z-scores to support diagnosis of different hematological diseases. Results We created percentile charts for hemoglobin, hematocrit, red cell indices, red cell count, red cell distribution width, white cell count and platelet count in girls and boys from birth to 18 years of age. Comparison of pediatricians evaluating complex clinical scenarios using percentile charts versus conventional/tabular representations shows that percentile charts can enhance physician assessment in selected example cases. Age-specific percentiles and z-scores, compared with absolute test results, improve the identification of children with blood count abnormalities and the discrimination between different hematological diseases. Conclusions The provided reference intervals enable precise assessment of pediatric hematology test results. Representation of test results using percentiles and z-scores facilitates their interpretation and demonstrates the potential of digital approaches to improve clinical decision-making.

Evaluation of the sensitivity and specificity of a novel line immunoassay for the detection of criteria and non-criteria antiphospholipid antibodies in comparison to established ELISAs

Background

Persistent antiphospholipid antibodies (aPL) constitute the serological hallmark of the antiphospholipid syndrome (APS). Recently, various new assay technologies for the detection of aPL better suited to multiplex reaction environments than ELISAs emerged. We evaluated the diagnostic performance of such a novel line immunoassay (LIA) for the simultaneous detection of 10 different aPL.

Methods

Fifty-three APS patients and 34 healthy controls were investigated for criteria (antibodies against cardiolipin [aCL], β2-glycoprotein I [aβ2-GPI]) and non-criteria aPL (antibodies against phosphatidic acid [aPA], phosphatidyl-choline [aPC], -ethanolamine [aPE], -glycerol [aPG], -inositol [aPI], -serine [aPS], annexin V [aAnnV], prothrombin [aPT]) IgG and IgM by LIA. Criteria aPL were additionally determined with the established Alegria (ALE), AcuStar (ACU), UniCap (UNI), and AESKULISA (AES) systems and non-criteria aPL with the AES system. Diagnostic performance was evaluated with a gold standard for criteria aPL derived from the results of the four established assays via latent class analysis and with the clinical diagnosis as gold standard for non-criteria aPL.

Results

Assay performance of the LIA for criteria aPL was comparable to that of ALE, ACU, UNI, and AES. For non-criteria aPL, sensitivities of the LIA for aPA-, aPI-, aPS-IgG and aPA-IgM were significantly higher and for aPC-, aPE-, aAnnV-IgG and aPC- and aPE-IgM significantly lower than AES. Specificities did not differ significantly.

Conclusions

The LIA constitutes a valuable diagnostic tool for aPL profiling. It offers increased sensitivity for the detection of aPL against anionic phospholipids. In contrast, ELISAs exhibit strengths for the sensitive detection of aPL against neutral phospholipids.

Anticoagulants of primary haemostasis

Inhibition of platelet function plays an important role in the treatment and secondary prevention of cardiovascular or cerebrovascular ischemic diseases. Established antiplatelet agents use different pharmacological targets for this role. Acetylic salicylic acid achieves a reduction of thromboxane A2 formation by inhibition of COX-1. Ticlopidin or clopidogrel are ADP-P2Y12 receptor antagonists. Tirofiban, abciximab or eptifibatid are used for the inhibition of the glycoprotein IIb/IIIa receptor which is activated at the surface of platelets preceding the final step of their aggregation. The mechanism of dipyridamole is based on the inhibition of adenosine uptake and of phosphodiesterase-5.

Efforts are made to improve antiplatetelet therapy with the aim to find agents with favorable clinical outcome and lower bleeding risk. Current clinical studies focus on a new generation of ADP receptor antagonists (prasugrel, cangrelor and ticagrelor) as successors of ticlopidin and clopidogrel after coronary arterial interventions. Developments using platelet targets different from established drugs are thrombin receptor antagonists (like SCH530348) or thromboxane receptor antagonists (like S18886/terutroban) in patients with cerebrovascular events. Results from recent experimental studies could lead to new strategies for antiplatetelet therapy (like inhibition of GP Ib receptor, GP VI receptor, platelet-leukocyte interaction, factor XII and others) in the future.

Evaluation of antiphospholipid antibody assays using latent class analysis to address the lack of a reference standard

BACKGROUND

Method evaluation of new assays for the detection of antiphospholipid antibodies (aPL) such as anti-cardiolipin (aCL) or anti-β2-glycoprotein I (aβ2-GPI) is challenging, as no internationally accepted reference material is available yet. Besides a lack of standardization, unacceptable inter-laboratory comparability of established tests is regularly observed. Owing to the absence of a commonly accepted reference standard, the evaluation of two research surface plasmon resonance (SPR) biosensor assays was performed using statistical methods from latent class analysis (LCA).

METHODS

aCL and aβ2-GPI IgG and IgM were measured in sera from 63 antiphospholipid syndrome patients, fulfilling the Sydney criteria, and in 34 healthy controls with four commercial assays. LCA was performed on the results and sera were assigned to the antibody-positive or antibody-negative group. Sera were subsequently evaluated in the SPR assays for aCL and aβ2-GPI. Optimal cutoffs and diagnostic performances of the research systems were established employing the LCA-derived gold standard.

RESULTS

With area under the curve results of 0.96 and 0.89 for the detection of aCL and aβ2-GPI, the research SPR assays discriminated well between antibody-positive and antibody-negative sera. Their sensitivities and specificities were comparable to the investigated commercial immunoassays.

CONCLUSIONS

SPR assays are a suitable tool for the detection of aCL and aβ2-GPI with diagnostic performances not different from currently available commercial tests. LCA enabled the calculation of sensitivities and specificities for aPL assays in absence of a reference standard.

Pediatric reference intervals for alkaline phosphatase

BACKGROUND

Interpretation of alkaline phosphatase activity in children is challenging due to extensive changes with growth and puberty leading to distinct sex- and age-specific dynamics. Continuous percentile charts from birth to adulthood allow accurate consideration of these dynamics and seem reasonable for an analyte as closely linked to growth as alkaline phosphatase. However, the ethical and practical challenges unique to pediatric reference intervals have restricted the creation of such percentile charts, resulting in limitations when clinical decisions are based on alkaline phosphatase activity.

METHODS

We applied an indirect method to generate percentile charts for alkaline phosphatase activity using clinical laboratory data collected during the clinical care of patients. A total of 361,405 samples from 124,440 patients from six German tertiary care centers and one German laboratory service provider measured between January 2004 and June 2015 were analyzed. Measurement of alkaline phosphatase activity was performed on Roche Cobas analyzers using the IFCC's photometric method.

RESULTS

We created percentile charts for alkaline phosphatase activity in girls and boys from birth to 18 years which can be used as reference intervals. Additionally, data tables of age- and sex-specific percentile values allow the incorporation of these results into laboratory information systems.

CONCLUSIONS

The percentile charts provided enable the appropriate differential diagnosis of changes in alkaline phosphatase activity due to disease and changes due to physiological development. After local validation, integration of the provided percentile charts into result reporting facilitates precise assessment of alkaline phosphatase dynamics in pediatrics.

Diagnostic performance study of an antigen microarray for the detection of antiphospholipid antibodies in human serum

The parallelization of clinically relevant antigens in a microarray format is of growing importance due to the ability to measure multiple antigen-antibody interactions. With the development of a microarray for the detection of antiphospholipid antibodies we focussed on one important autoimmune disease that is still diagnostically challenging. Reasons are the heterogeneity of the autoantibodies and the unspecific clinical symptoms.

For the covalent immobilization of antigenic structures, glass transducers were coated with 11-aminoundecyltrimethoxysilane (11-AUTMS). In total 35 antiphospholipid syndrome (APS) patients, six patients with lupus erythematosus and 24 healthy controls were investigated on a microarray format using polarized imaging reflectometric interference spectroscopy.

The novel surface modification based on the short derivative 11-AUTMS resulted in a selective biosensor allowing a clear differentiation of patient and control samples. It combined proteinogenic as well as phospholipid-derived antigens, namely β

Multiplexed determination of serological parameters has a great potential. We have shown that our biosensor is capable of detecting four different APS relevant antibodies in parallel exhibiting a sensitivity and specificity comparable to existing ELISA methods.

Reference ranges for analytes of thyroid function in children

Promptly detecting pediatric thyroid dysfunction requires age-appropriate reference ranges for serum thyroid-stimulating hormone (TSH), serum free thyroxine (FT4), and serum free triiodothyronine (FT3). We sought to establish such ranges, employing the widely-used Immulite® 2000 automated immunoluminometric assays in a large population. We assayed the analytes according to manufacturer's instructions in serum samples from 359 male and 297 female university hospital patients, aged between newborn to 18 years, without evidence of thyroid or pituitary dysfunction. As data were not normally distributed, the reference ranges were assumed to lie between the 2.5th and 97.5th percentiles. Curves for age-related changes in the reference ranges were calculated using the linearity, median and skewness method. TSH, FT4, and FT3 reference ranges showed a wide spread immediately after birth, rapidly decreasing within the first 2 years of life. Reference range width was fairly stable after about age 4 years. However, from that time, the ranges' lower and upper limits steadily declined, essentially reaching (FT3) or approximating (TSH, FT4) healthy adult values by age 18 years. Age-specific reference ranges should be used when measuring TSH, FT4, and FT3 in children. During very early life, values of these analytes range widely, making it challenging to interpret measurements in infants, and, especially, newborns.

The new INNOVANCE® PFA P2Y cartridge is sensitive to the detection of the P2Y₁₂ receptor inhibition

Insufficient response on antiplatelet medication has become an intensively discussed issue because of the risk factor of recurrent adverse cardiovascular events. However, the monitoring of antiplatelet therapy requires appropriate, robust and reliable test methods. For the measurement of thienopyridine effects, the manufacturer of the PFA-100® System provides the INNOVANCE® PFA P2Y * cartridge. We tested this cartridge for its capacity to detect the inhibition of the P2Y₁₂ receptor, which is the target for thienopyridine medication (e.g. clopidogrel). We compared the INNOVANCE® PFA P2Y * results with those obtained by the receptor specific flow cytometric vasodilator stimulated phosphoprotein (VASP) assay that expresses the status of the P2Y₁₂ receptor as "platelet reactivity index" (PRI). The in vitro addition of the P2Y₁₂ receptor antagonist cangrelor (AR-C69931MX) to citrated human whole blood resulted in a dose-dependent prolongation of closure times (CTs) of the INNOVANCE® PFA P2Y * cartridge correlating with decreased PRI levels. In volunteers, the intake of a 600 mg clopidogrel loading dose caused an increase of the CTs in all volunteers, although some of these volunteers were identified as "poor responders" by the VASP assay (no significant reduction of PRI levels). In 50 patients with stable coronary artery disease undergoing percutaneous coronary intervention (PCI) and under dual antiplatelet therapy, the new cartridge had a detection rate of 84% (CT 106 s as cut-off) for clopidogrel medication. After dividing the 50 patients into two groups according to their response to clopidogrel INNOVANCE® PFA P2Y * recognized all "responders" (defined by a PRI > 50%) using >106 s as cut-off but the specificity for a "good response" was only 42% because several "poor responders" (defined by a PRI > 50%) also showed CTs above the cut-off. The best correlation (substantial agreement) between the results of INNOVANCE® PFA P2Y * and of the VASP phosphorylation assay was achieved using CT > 200 s and PRI < 55% as cut-offs. Then, the sensitivity of INNOVANCE® PFA P2Y * was 97% and the specificity for a "good response" 65%. In summary, INNOVANCE® PFA P2Y * showed a high sensitivity for the detection of P2Y₁₂ receptor blockade, but had only a limited specificity for a "good response" to clopidogrel. Therefore, this new cartridge is a useful tool to rule out P2Y₁₂ receptor inhibition, if normal or only slightly prolonged CTs are obtained. Its predictive value for risk assessment of thromboembolic events, e.g. after coronary stent implantation, needs to be evaluated in clinical trials.

Standardized antigen preparation to achieve comparability of anti-beta2-glycoprotein I assays

INTRODUCTION

The Sydney classification for diagnosis of the antiphospholipid syndrome (APS) first introduced the determination of anti-beta2-glycoprotein I (anti-beta2-GPI)-antibodies in serum as laboratory criteria. In this context, widely differing results of anti-beta2-GPI assays are a concerning issue. Considerable efforts have been made to optimize ELISAs, however little attention was hitherto spent to the antigen preparation. We evaluated the influence of different beta2-GPI preparations on the ability to separate ill and healthy patients and on the comparability of anti-beta2-GPI-assays.

MATERIALS AND METHODS

Microplates were coated with various beta2-GPI preparations and anti-beta2-GPI IgG- and IgM-ELISAs were performed for 21 APS patients and 21 controls using the monoclonal calibrators HCAL and EY2C9. Subsequently, by use of a surface plasmon resonance (SPR) biosensor, affinity constants for the HCAL- and EY2C9-interaction with each beta2-GPI preparation were determined and antigen binding of sera of APS patients and controls was studied.

RESULTS

All ss2-GPI preparations showed good discrimination ability ill vs. healthy but poor inter-assay comparability in the ELISAs. Affinity constants for HCAL and EY2C9 were independent of the beta2-GPI variant (K(A) 0.105 - 0.200 and 0.449 - 1.04 x 10(10)M(-1); K(D) 50.0 - 95.5 and 9.61 - 22.3 x 10(-11)M, respectively). In the biosensor, reactivity to the different beta2-GPIs was negligible for the controls and varied considerably for patients.

CONCLUSION

Inter-assay comparability of anti-beta2-GPI ELISAs is highly dependent upon the beta2-GPI preparation. Only agreement on one common beta2-GPI preparation will improve the requested inter-assay comparability.

Prostacyclin receptor stimulation facilitates detection of human platelet P2Y(12) receptor inhibition by the PFA-100 system

The rationale for monitoring platelet inhibition by thienopyridines for the identification of patients at risk for future recurrent arterial thrombosis or ischemic events is intensively discussed, as well as which monitoring systems are appropriate, robust and reliable. Flow cytometric measurement of phosphorylated VASP (vasodilator-stimulated phosphoprotein), expressed as platelet reactivity index (PRI), is presently "the gold standard method" for evaluating P2Y(12) receptor inhibition. The PFA-100 system, a commercially available and clinically widely used platelet test system, is based on a different principle, not that of VASP phosphorylation. The aim of the present study was to compare the two methods and evaluate whether the conventional PFA-100 collagen/ADP cartridge could be pharmacologically improved to enable its routine clinical use for detection of platelet P2Y(12) receptor inhibition. The effects of increasing concentrations of the competitive P2Y(12) receptor antagonist cangrelor (AR-C69931MX) and the time-dependent effects of a single oral loading dose of clopidogrel (600 mg) were analysed with human whole blood. P2Y(12) receptor inhibition was measured by the VASP/PRI assay and the PFA-100 collagen/ADP cartridge system, with and without preincubation with the prostacyclin analog iloprost (Ilomedin). In vitro addition of iloprost (0.5 nM) enabled PFA-100 collagen/ADP cartridge system detection of P2Y(12) receptor inhibition in whole blood by cangrelor in vitro or by clopidogrel treatment of volunteers. The addition of a prostacyclin analog facilitates PFA-100 collagen/ADP system detection of P2Y(12) receptor inhibition, achieving a sensitivity similar to that of the VASP/PRI reference method. Future studies should now evaluate whether this modified PFA-100 system, like the VASP assay, is a reliable test system for monitoring P2Y(12) receptor inhibition under clinical conditions.

[Anticoagulants of primary haemostasis]

Inhibition of platelet function plays an important role in the treatment and secondary prevention of cardiovascular or cerebrovascular ischemic diseases. Established antiplatelet agents use different pharmacological targets for this role. Acetyl salicylic acid achieves a reduction of thromboxane A2 formation by inhibition of COX-1. Ticlopidine or clopidogrel are ADP-P2Y12 receptor antagonists. Tirofiban, abciximab or eptifibatid are used for the inhibition of the glycoprotein IIb/IIIa receptor which is activated at the surface of platelets preceding the final step of their aggregation. The mechanism of dipyridamole is based on the inhibition of adenosine uptake and of phosphodiesterase-5. Efforts are made to improve antiplatelet therapy with the aim to find agents with favorable clinical outcome and lower bleeding risk. Current clinical studies focus on a new generation of ADP receptor antagonists (prasugrel, cangrelor and ticagrelor) as successors of ticlopidine and clopidogrel after coronary arterial interventions. Developments using platelet targets different from established drugs are thrombin receptor antagonists (like SCH530348) or thromboxane receptor antagonists (like S18886/terutroban) in patients with cerebrovascular events. Results from recent experimental studies could lead to new strategies for antiplatelet therapy (like inhibition of GP Ib receptor, GP VI receptor, platelet-leukocyte interaction, factor XII and others) in the future.

Monitoring of Clopidogrel Action: Comparison of Methods

Background: Clopidogrel is a potent drug for prevention of adverse effects during and after coronary intervention. Increasing experience indicates that a significant proportion of patients do not respond adequately to clopidogrel. Because failure of antiplatelet therapy can have severe consequences, there is need for a reliable assay to quantify the effectiveness of clopidogrel treatment.

Methods: Of 24 healthy volunteers admitted to the study, 18 were treated for 1 week with clopidogrel (300-mg loading dose and 75-mg maintenance dose), and 6 with placebo. Platelet function was monitored by 2 assays, based on flow cytometry and enzyme immunoassay, that measure the phosphorylation status of vasodilator-stimulated phosphoprotein (VASP) and by aggregometry, flow cytometry of P-selectin, and the platelet function analyzer at baseline, on days 1–5, and on day 9 of treatment.

Results: Aggregometry and VASP phosphorylation revealed a loss of platelet response to ADP within 12 h after clopidogrel intake. The phosphorylation status of VASP correlated with the inhibition of platelet aggregation. In contrast, neither P-selectin expression nor PFA-100 closure time was a clear indicator of clopidogrel effects on platelets.

Conclusions: VASP phosphorylation assays are reliable for quantifying clopidogrel effects. Because the VASP assay directly measures the function of the clopidogrel target, the P2Y12 receptor, the assay is selective for clopidogrel effects rather than effects of other platelet inhibitors commonly in use.

Workflow and cost analysis on MODULAR ANALYTICS

Four stand-alone analyzers in a centralized laboratory were replaced by two modular analytical systems processing 45 methods of the general chemistry and specific protein segment. This consolidation led to a reduction of the daily workflow and operational costs. The cost saving with 1.3 million reported results per year was 53,000 Euro, which can be assessed as an important contribution to cost reduction in the health care system.

Atypical spontaneous factor VIII inhibitor: specific diagnostics and therapy of acute bleeding

Differentiation of rapidly binding coagulation factor inhibitors from antiphospholipid antibodies is a challenge for the hemostaseologic laboratory, especially with respect to the different therapeutic consequences. Several immunological and functional assays for the diagnosis of these disorders have been proposed. Here we report the clinical and laboratory findings of a 65-year-old man who developed severe bleeding after a tooth extraction. The process leading to the diagnosis of a spontaneous atypical factor VIII inhibitor and the value of different laboratory tests are discussed.

Centrifugal and roller pumps--are there differences in coagulation and fibrinolysis during and after cardiopulmonary bypass?

A number of hemostatic parameters reflecting the activation of coagulation and fibrinolysis were investigated in a prospective study of 24 patients undergoing cardiopulmonary bypass (CPB) during heart surgery. The patients were randomized to a group in which either a roller (group 1) or a centrifugal pump (group 2) was used. Blood samples were taken preoperatively, at the onset of and every 20 min during CPB, after the administration of protamine, and 4, 20, 44, and 68 h postoperatively. The groups did not differ significantly in hematocrit, fibrinogen, factor XIII, and antithrombin III. Significant differences in favor of group 2 during and after CPB were found in prothrombin fragment F1 + 2, plasmin-antiplasmin complex (PAP), thrombin-antithrombin complex (TAT), and D-dimer (F1 + 2 P < 0.01 after 80-min CPB, PAP P < 0.005 after 40-min CPB, TAT and D-dimer P < 0.05 after 100-min CPB, D-dimer and PAP P < 0.05 after protamine administration, TAT and F1 + 2 4 h after CPB). These findings indicate the activation of fibrinolysis preceding thrombin generation during cardiopulmonary bypass. In addition, we conclude that centrifugal blood pumping is beneficial in avoiding excessive activation of both coagulation and fibrinolysis.

[Splenic rupture after minor accident. Significant intra-abdominal hemorrhage is tolerated without symptoms]

In the framework of a case report the difficulty caused by splenic rupture after a minor trauma is discussed. In the case reported considerable asymptomatic bleeding into the abdominal cavity took place, which was only diagnosed accidentally by intravaginal ultrasound performed to exclude the tentative diagnosis of an endometrial carcinoma.

[Diagnosis of female urinary incontinence. Progress with urodynamic functional diagnosis]

PROBLEM

Owing to its frequency and severe consequences for the women affected, urinary incontinence poses a considerable problem. Our knowledge about its pathophysiology, as also the diagnostic and therapeutic possibilities, remain remarkably limited.

TYPES OF INCONTINENCE

The main types of incontinence are stress, urge, reflex and overflow incontinence. Other forms are rare. A major diagnostic and therapeutic problem is posed by the mixed type, which can account for up to 60 percent.

DIAGNOSTIC EVALUATION

Owing to the morphologically and functionally complex nature of the lower urinary tract, the diagnostic approach to incontinence must involve various levels, and comprises careful history taking, a thorough physical examination, and special urodynamic evaluation.

THERAPEUTIC CONCEPTS

Abundant therapeutic approaches, both pharmacological and surgical, are available, but opinion as to what constitutes the best therapeutic concept varies greatly.

CONCLUSION

Despite the only moderate chances of successful treatment under realistic conditions, our present knowledge about the diagnosis and treatment of female urinary incontinence needs to become more widespread.