Role of platelet gene polymorphisms in ischemic pediatric stroke subtypes: a case-control study.

AIM: To assess the role of human platelet antigens (HPA), P-selectin gene (SELP) polymorphisms, and HPA and SELP haplotypes with factor V (FV) R506Q in ischemic pediatric stroke (IPS) subtypes: cerebral sinovenous thrombosis (CSVT), perinatal (PAIS), and childhood (CAIS) arterial ischemic stroke. METHODS: This case-control study enrolled 150 children with confirmed IPS and 150 age- and sex-matched controls. FV R506Q and HPA-1 were genotyped with CVD StripAssay®, HPA-2 and HPA-3 with real-time polymerase chain reaction, SELP S290N, V599L, and T715P with high resolution melting analysis, and SELP N562D with sequence-specific polymerase chain reaction. RESULTS: HPA-1b allele (odds ratio [OR] 2.75, 95% confidence interval [CI] 1.02-7.42, P=0.048) and HPA-1a2a3b (OR 5.46, 95% CI 1.51-19.76, P=0.011), HPA-1b2a3a (OR 7.00, 95% CI 1.25-39.13, P=0.028), and HPA-1b2b3a (OR 11.39, 95% CI 1.39-92.95, P=0.024) haplotypes increased the risk for CSVT. HPA-3b allele was significantly associated with 2-fold lower risk for PAIS (OR 0.49, 95% CI 0.26-0.89, P=0.020) and CAIS (OR 0.47, 95% CI 0.26-0.86, P=0.014) and non-significantly associated with increased risk for CSVT (OR 6.43, 95% CI 0.83-50.00, P=0.022). HPA-1a2b3a haplotype was significantly associated with CAIS (OR 6.76, 95% CI 2.13-21.44, P=0.001). The inclusion of FV R506Q in SELP haplotype analysis increased the risk for PAIS 4-fold in QNDVT carriers (OR 8.14, 95% CI 0.93-71.33, P=0.060) compared with NDVT haplotype (OR 2.45, 95% CI 0.98-6.18, P=0.058), but the result was not significant. CONCLUSION: Individual HPAs, and particularly HPA haplotypes, are involved in IPS subtypes pathogenesis. A possible risk-inducing synergistic effect of SELP haplotypes with FV R506Q is restricted to PAIS only.

The characteristics of transcranial color-coded duplex sonography in children with cerebral arteriovenous malformation presenting with headache.

PURPOSE: Cerebral arteriovenous malformations (AVM) are uncommon lesions. They are most often presented in childhood as intracranial hemorrhage. The aim of this report is to present the use of transcranial color-coded duplex sonography (TCCS) in detection of AVMs in children suffering headache. METHODS: This report describes five pediatric patients with headache and cerebral AVM which were initially discovered by TCCS. Diagnosis was confirmed by magnetic resonance imaging and digital subtraction angiography. RESULTS: In all patients, TCCS showed saccular enlargement of the vessels with a multicolored pattern corresponding to the different directions of blood flow. Spectral analysis showed significantly high flow systolic and diastolic velocities and low resistance index. CONCLUSIONS: In this report, we describe TCCS as a valuable non-invasive, harmless, low-cost, widely available method for the detection and follow-up of hemodynamic changes of AVMs in children with headache, before and after treatment.

Peer groups splitting in Croatian EQA scheme: a trade-off between homogeneity and sample size number.

BACKGROUND: Laboratory evaluation through external quality assessment (EQA) schemes is often performed as 'peer group' comparison under the assumption that matrix effects influence the comparisons between results of different methods, for analytes where no commutable materials with reference value assignment are available. With EQA schemes that are not large but have many available instruments and reagent options for same analyte, homogenous peer groups must be created with adequate number of results to enable satisfactory statistical evaluation. We proposed a multivariate analysis of variance (MANOVA)-based test to evaluate heterogeneity of peer groups within the Croatian EQA biochemistry scheme and identify groups where further splitting might improve laboratory evaluation. METHODS: EQA biochemistry results were divided according to instruments used per analyte and the MANOVA test was used to verify statistically significant differences between subgroups. The number of samples was determined by sample size calculation ensuring a power of 90% and allowing the false flagging rate to increase not more than 5%. When statistically significant differences between subgroups were found, clear improvement of laboratory evaluation was assessed before splitting groups. RESULTS: After evaluating 29 peer groups, we found strong evidence for further splitting of six groups. Overall improvement of 6% reported results were observed, with the percentage being as high as 27.4% for one particular method. CONCLUSIONS: Defining maximal allowable differences between subgroups based on flagging rate change, followed by sample size planning and MANOVA, identifies heterogeneous peer groups where further splitting improves laboratory evaluation and enables continuous monitoring for peer group heterogeneity within EQA schemes.

Determination of l-Asparaginase Activity and Its Therapeutic Monitoring in Children with Hematological Malignancies in a Single Croatian Center.

BACKGROUND: Among malignant diseases which develop during childhood, hematological cancers, such as leukemias and lymphomas, are the most common. Outcomes have greatly improved due to the refinement of multiagent chemotherapy regimens that include enhanced asparaginase therapy. In this study, we aimed to evaluate our experiences related to the analytical and clinical significance of determining l-Asparaginase activity. METHODS: Since 2016, the Laboratory of the Children's Hospital Zagreb has routinely measured l-Asparaginase activity and to date, has measured more than 280 examples of activity in a total of 57 children with hematological malignancy treated at the Pediatric Oncology Department of the Children's Hospital Zagreb. Three asparaginase products were available: native E. colil-Asparaginase; a pegylated form of this enzyme; and a native product from Erwinia chrysanthemi. A retrospective data analysis was performed. RESULTS: Out of the fifty-seven children, seven had an allergic reaction (12.3%), five (8.8%) had silent inactivation, and seven (12.3%) developed acute pancreatitis. Allergic reactions and silent inactivation were more common in children treated with native E. colil-Asparaginase, while pancreatitis was more common in children treated with the pegylated form. CONCLUSIONS: The monitoring of l-Asparaginase activity may help to optimize therapy by identifying patients with 'silent inactivation', and/or by dose correction when l-Asparaginase activity is too high (slow elimination).

Clinical and Analytical Comparison of Monoclonal and Polyclonal Immunoassays for Fecal Pancreatic Elastase.

BACKGROUND: Numerous immunoassays have been commercialized to determine pancreatic elastase (PE) in feces in screening for exocrine pancreatic insufficiency (EPI), but how the different assays compare to one another is controversial, especially in the context that all methods use the same cut-off values for interpreting the results obtained on the presence or absence of EPI or the degree of insufficiency if it is present. Our aim was to analytically verify a new method for determining PE, compare the results with a previous method, and verify the declared cut-off values for interpretation of the results. METHODS: PE in the stool was assayed using a previous monoclonal enzyme-linked immunosorbent assay ("ScheBo ELISA") and a new polyclonal particle-enhanced turbidimetric immunoassay ("Bühlmann PETIA"). The direct method comparison of two immunoassays was performed in 40 samples. Clinical comparisons were conducted against each other for the binary determination of "abnormal/normal" elastase levels and the three-way determination of "severe/moderate/no" EPI in 56 samples. The indirect comparison method used external quality assessment (EQA) data to compare the monoclonal and polyclonal immunoassays for PE, and additionally compare the monoclonal ScheBo ELISA to a monoclonal chemiluminescence immunoassay ("DiaSorin CLIA"). RESULTS: Precision in the series and intra-laboratory precision for Bühlmann PETIA met the manufacturer's specifications for the concentration range of limit/lower values and the range of normal values. The Bühlmann PETIA immunoassay on different analytical platforms yielded comparable results and nearly perfect agreement in the case of three-way classification (kappa = 0.89 with 95%CI from 0.79 to 1.00. ScheBo ELISA tends to generate higher values of pancreatic elastase than the Bühlmann PETIA; agreement between the methods was moderate in the case of binary classification (kappa = 0.43; 95% CI 0.25 to 0.62), and substantial in the case of three-way classification (kappa = 0.62; 95% CI 0.50 to 0.75). EQA data analysis showed a statistically significant difference between ScheBo ELISA and Bühlmann PETIA peer groups (p = 0.031), as well as the DiaSorin CLIA and ScheBo ELISA peer groups (p = 0.010). CONCLUSION: The ScheBo ELISA and Bühlmann PETIA do not appear to be commutable in the analytical and clinical context. Our data address a discordance between different mono- and polyclonal immunoassays for pancreatic elastase and the potential of misclassification using its universal cut-off values in screening suspected patients for exocrine pancreatic insufficiency.

Multiple presence of prothrombotic risk factors in Croatian children with arterial ischemic stroke and transient ischemic attack.

AIM: To determine the frequency of inherited and acquired prothrombotic risk factors in children with arterial ischemic stroke (AIS) and transient ischemic attacks (TIA) in Croatia. METHODS: We investigated 14 prothrombotic risk factors using blood samples from 124 children with AIS or TIA and 42 healthy children. Prothrombotic risk factors were classified into five groups: natural coagulation inhibitors (antithrombin, protein C, protein S), blood coagulation factors (FV Leiden and FII 20210), homocysteine, lipid and lipoprotein profile (lipoprotein (a), triglycerides, total, high- and low-density lipoprotein), and antiphospholipid antibodies (lupus anticoagulant, anticardiolipin, and antiphosphatidylserine antibodies). RESULTS: The most common prothrombotic risk factor was elevated lipoprotein (a), which was identified in about 31% of patients and in 24% of controls. Natural coagulation inhibitors were decreased in about 19% of patients, but not in controls. Pathological values of homocysteine, blood coagulation factor polymorphisms, and antiphospholipid antibodies were found in similar frequencies in all groups. Fourteen children with AIS and TIA (11.3%) and no children from the control group had three or more investigated risk factors. CONCLUSION: The presence of multiple prothrombotic risk factors in children with cerebrovascular disorder suggests that a combination of risk factors rather than individual risk factors could contribute to cerebrovascular disorders in children.

Pseudocholinesterase activity in cerebrospinal fluid as a biomarker of solid central nervous system tumors in children.

AIM: To determine the activity of pseudocholinesterase (PChE) in cerebrospinal fluid (CSF) and serum in children with solid central nervous system (CNS) tumor and to assess whether PChE activity could be a valid biomarker for solid CNS tumors in children. METHODS: The study and control group included 30 children each. Children in the study group had a solid CNS tumor, while those from the control group had never suffered from any tumor diseases. CSF and serum samples were collected from all participants and PChE activity was determined using the Ellman's spectrophotometric method. PChE activity in CSF was shown as a cerebrospinal fluid/serum ratio expressed in percentage, ie, PChE CSF/serum ratio. Receiver operating characteristic (ROC) curve was used to assess whether PChE activity can be used as a biomarker for identifying children with solid CNS tumors. RESULTS: Children with solid CNS tumor had significantly higher PChE activity in CSF and serum, as well as PChE CSF/serum ratio (P=0.001). PChE CSF/serum ratio in the study group was 2.38% (interquartile range [IQR] 1.14-3.97) and 1.09% (IQR 0.95-1.45) in the control group. ROC curve analysis of PChE CSF/serum ratio resulted in an area under the curve (AUC) value of 0.76 (95% confidence interval [CI] 0.63-0.88) and a cut-off of 1.09. Twenty five of 29 patients with elevated PChE CSF/serum ratio had a tumor, corresponding to a sensitivity of 83% and a specificity of 53%. CONCLUSION: PChE CSF/serum ratio may be used as a test or biomarker with good sensitivity for solid CNS tumors in children.

Analytical verification of the Dymind D7-CRP automated analyser.

Introduction: The aim of this study was to perform a verification of the Dymind D7-CRP automated analyser and compare it with established analysers. Materials and methods: Analytical verification included estimation of repeatability, between run precision, within-laboratory precision, and bias in control samples with low, normal and high levels. The acceptance criteria for analytical verification were defined using the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) 2019 Biological Variation Database. Method comparison between the Dymind D7-CRP and the Sysmex XN1000 for haematological parameters and the Dymind D7-CRP and the Beckman Coulter AU680 for CRP values was performed on 40 patient samples. Results: Analytical verification criteria were adequately met with the exception of monocyte count for repeatability and within-laboratory precision (13.4% and 11.5%, respectively, acceptance criteria 10.1%) and measurement uncertainty (23.0, acceptance criteria 20.0%) at low level, eosinophil count for BIAS at the low level (37.7%, acceptance criteria 25.2%), basophil count (BAS) for BIAS at the high level (14.2%, acceptance criteria 10.9%), and mean platelet volume (MPV) for repeatability (4.2% and 6.8%), between run precision (2.2% and 4.7%), within-laboratory precision (4.0% and 7.3%) (acceptance criteria 1.7%), and measurement uncertainty (8.0 and 14.6%, acceptance criteria 3.4%) at both the low and high concentrations. Method comparison showed no clinically significant constant or proportional differences for all parameters except BAS and MPV. Conclusion: The analytical verification of the Dymind D7-CRP showed adequate analytical characteristics. The Dymind D7-CRP can be used interchangeably with the Sysmex XN-1000 for all parameters tested, except BAS and MPV, and with the Beckman Coulter AU-680 for the determination of CRP.

Interpretative comments - need for harmonization? Results of the Croatian survey by the Working Group for Post-analytics.

INTRODUCTION: Interpretation of laboratory test results is a complex post-analytical activity that requires not only understanding of the clinical significance of laboratory results but also the analytical phase of laboratory work. The aims of this study were to determine: 1) the general opinion of Croatian medical biochemistry laboratories (MBLs) about the importance of interpretative comments on laboratory test reports, and 2) to find out whether harmonization of interpretative comments is needed. MATERIALS AND METHODS: This retrospective study was designed as a survey by the Working Group for Post-analytics as part of national External Quality Assessment (EQA) program. All 195 MBLs participating in the national EQA scheme, were invited to participate in the survey. Results are reported as percentages of the total number of survey participants. RESULTS: Out of 195 MBLs, 162 participated in the survey (83%). Among them 59% MBLs implemented test result comments in routine according to national recommendations. The majority of laboratories (92%) state that interpretative comments added value to the laboratory reports, and a substantial part (72%) does not have feedback from physicians on their significance. Although physicians and patients ask for expert opinion, participants stated that the lack of interest of physicians (64%) as well as the inability to access patient's medical record (62%) affects the quality of expert opinion. CONCLUSION: Although most participants state that they use interpretative comments and provide expert opinions regarding test results, results of the present study indicate that harmonization for interpretative comments is needed.

Achromobacter xylosoxidans Purulent Bronchitis in a Previously Healthy Child: An Unexpected Consequence of COVID-19 Infection.

Achromobacter xylosoxidans is an aerobic, Gram-negative rod with a broad intrinsic and acquired antimicrobial resistance, usually isolated in patients with cystic fibrosis (CF), immunodeficiencies, or those undergoing invasive procedures. We report a case of a previously healthy 14-year-old girl who was hospitalized in our institution due to a prolonged, progressive cough and exertional dyspnea, which started after a mild viral respiratory tract infection. To elucidate the cause of her symptoms, a bronchoscopy was finally performed, showing bilateral purulent bronchitis caused by A. xylosoxidans, isolated from bronchoalveolar lavage (BAL) sample. Since the patient had positive serological testing for coronavirus disease 2019 (COVID-19), we concluded that it was the initial viral infection, although of a mild clinical course, the one that created favorable conditions for proliferation and further inflammation caused by A. xylosoxidans.

Urinary brain-derived neurotrophic factor and nerve growth factor as noninvasive biomarkers of overactive bladder in children.

Introduction: Overactive bladder (OAB) is the most common urinary disorder and the leading cause of functional daytime intermittent urinary incontinence in children. The aim of this study was to determine whether urinary brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) concentrations, normalized to urine creatinine, could be used as biomarkers for diagnosis and treatment monitoring of OAB in children. Materials and methods: Urine samples of 48 pediatric patients with OAB were collected at the start of anticholinergic therapy (baseline), at follow-up visits (3 and 6 months), and from 48 healthy controls. Urinary BDNF and NGF concentrations were determined by ELISA method (Merck, Darmstadt, Germany) and Luminex method (Thermo Fisher Scientific, Waltham, USA). Differences of frequency between quantifiable analyte concentrations between subject groups were determined using Fisher's exact test. Results: There was no statistically significant difference between quantifiable analyte concentrations between patients at baseline and the control group for BDNF and NGF by either the ELISA or Luminex method (P = 1.000, P = 0.170, P = 1.000, and P = N/A, respectively). There was a statistically significant difference between quantifiable BDNF by the ELISA method between patients at baseline and complete success follow-up (P = 0.027), while BDNF by Luminex method and NGF by both methods were not statistically significant (P = 0.078, P = 0.519, and P = N/A, respectively). Conclusions: This study did not demonstrate that urinary BDNF and NGF concentrations, can be used as biomarkers for diagnosis and therapy monitoring of OAB in children.

National Guidelines for the Performance of the Sweat Test in Diagnosis of Cystic Fibrosis on behalf of the Croatian Society of Medical Biochemistry and Laboratory Medicine and the Cystic Fibrosis Centre - Paediatrics and adults, University Hospital Centre Zagreb.

The sweat test (ST) is a cornerstone in the diagnosis of cystic fibrosis (CF), together with newborn screening and genetic testing. However, the performance of the ST can depend on the operator's skill, so several international guidelines have been published to standardise the ST, but inconsistencies remain. The joint Working Group for ST Standardisation (WG STS) of the Croatian Society of Medical Biochemistry and Laboratory Medicine, in association with cistic fybrosis health professional and the Cistic Fibrosis Centre for Paediatrics and Adults, have issued National Guidelines for the Performance of the Sweat Test in order to ensure consistency in ST performance and accuracy of reported results. Many of the standards were taken from the 2nd Edition of the UK Guidelines for Performance of the ST for the Diagnosis of CF, while others were taken from independent consensus statements from the WG STS based on local ST equipment and practices. The standards cover every step of the ST, from the indications for testing to reporting of results and their interpretation, including the analytical phase and quality control. In addition, National Guidelines include appendices with practical examples in order to aid implementation of the recommendations in routine practice.

Laboratory policies and practices for thyroid function tests in Croatia: survey on behalf of Working Group for Laboratory Endocrinology of the Croatian Society of Medical Biochemistry and Laboratory Medicine.

Introduction: Laboratory plays important part in screening, diagnosis, and management of thyroid disorders. The aim of this study was to estimate current laboratory preanalytical, analytical and postanalytical practices and policies in Croatia. Materials and methods: Working Group for Laboratory Endocrinology of the Croatian Society of Medical Biochemistry and Laboratory Medicine designed a questionnaire with 27 questions and statements regarding practices and protocols in measuring thyroid function tests. The survey was sent to 111 medical biochemistry laboratories participating in external quality assurance scheme for thyroid hormones organized by Croatian Centre for Quality Assessment in Laboratory Medicine. Data is presented as absolute numbers and proportions. Results: Fifty-three participants returned the questionnaire. Response rate varied depending on question, yielding a total survey response rate of 46-48%. All respondents perform thyroid stimulating hormone (TSH). From all other thyroid tests, most performed is free thyroxine (37/53) and least TSH-stimulating immunoglobulin (1/53). Laboratories are using nine different immunoassay methods. One tenth of laboratories is verifying manufacturer's declared limit of quantification for TSH and one third is verifying implemented reference intervals for all performed tests. Most of laboratories (91%) adopt the manufacturer's reference interval for adult population. Reference intervals for TSH are reported with different percentiles (90, 95 or 99 percentiles). Conclusion: This survey showed current practices and policies in Croatian laboratories regarding thyroid testing. The results identified some critical spots and will serve as a foundation in creating national guidelines in order to harmonize laboratory procedures in thyroid testing in Croatia.

The concurrence of the current postanalytical phase management with the national recommendations: a survey of the Working Group for Postanalytics of the Croatian Society of Medical Biochemistry and Laboratory Medicine.

INTRODUCTION: The detection and prevention of errors in the postanalytical phase can be done through the harmonization and standardization of constituent parts of this phase of laboratory work. The aim was to investigate how well the ongoing management of the postanalytical phase corresponds to the document "Post-analytical laboratory work: national recommendations" in Croatian medical biochemistry laboratories (MBLs). MATERIALS AND METHODS: All 195 MBLs participating in the national external quality assessment scheme, were invited to undertake a part in a survey. Through 23 questions the participants were asked about management of the reference intervals (RI), delta check, reflex/reflective testing, postanalytical quality indicators and other parts of the postanalytical phase recommended in the national recommendations. The results are presented in numbers and percentages. RESULTS: Out of 195 MBLs, 119 participated in the survey, giving a response rate of 61%. Not all of the respondents provided answers to all the questions. Delta check has not been used in 59% (70/118) of the laboratories. Only 22/113 (20%) laboratories use reflex and/or reflective testing. In 53% of the laboratories, critical results were reported within 30 minutes of the confirmation of the results. In 34% (40/118) of the laboratories, turnaround time and reporting of critical results are two most often monitored postanalytical quality indicators. CONCLUSION: The results showed the critical results reporting and monitoring of postanalytical quality indicators are in the line with the recommendations. However, the management of RI verification, the use of delta check and reflex/reflective testing still must be harmonized among Croatian MBLs.

Association of fibrinogen and plasmin inhibitor, but not coagulation factor XIII gene polymorphisms with coronary artery disease.

BACKGROUND: In the final phase of clot formation, fibrinogen constitutes frame, whereas factor XIII (FXIII) active form is responsible for the covalent cross-linking of fibrin fibres and plasmin inhibitor (PI), thus contributing to clot stability. It could be expected that any change of coagulation factors' structure affects the clot formation and modulates the atherothrombotic risk. The aim was to determine the frequency of four single nucleotide polymorphisms: (i) A > G in codon 312 of the fibrinogen α-chain gene (rs6050, Thr312AlaFGA), (ii) C > T at position 10034 of the 3 - untranslated region in the fibrinogen γ-chain gene (rs2066865, 10034C > T FGG), (iii) C > T in codon 564 of the FXIII-A subunit gene (rs5982, Pro564LeuFXIII-A), and (iv) C > T in codon 6 of the plasmin inhibitor gene (rs2070863, Arg6TrpPI) in Croatian patients and their association with coronary artery disease (CAD). METHODS: We performed the unrelated case-control association study on the consecutive sample of patients 18 years old, who had undergone coronary angiography for investigation of chest pain and suspected CAD. The cases were patients with confirmed CAD (N=201), and the controls were the subjects with no CAD (N=119). Samples were genotyped using PCR-RFLP analysis. RESULTS: Observed frequencies of the rare alleles of Thr312Ala FGA, 10034C > T FGG, Leu564Pro FXIII-A and Arg6Trp PI polymorphisms were 21%, 17%, 14%, 20%, respectively. Patients with 10034C > T FGG CC genotype had 3.5 times (95% CI 1.02-12.03) higher adjusted odds for CAD than patients with 10034C > T FGG TT genotype. Patients with Arg6Trp PI CC genotype had 3.86 times (95% CI 1.23-12.12) higher odds for CAD than patients with Arg6Trp PI TT genotype. It seems that those genotype-related higher odds are also male-gender related. No difference was observed regarding any other investigated polymorphism. CONCLUSIONS: Our finding suggests that 10034C > T FGG and Arg6Trp PI are associated with CAD.

Fecal Calprotectin as a Biomarker of Food Allergy and Disease Severity in Children with Atopic Dermatitis without Gastrointestinal Symptoms.

Fecal calprotectin (FCP) is a biomarker of intestinal inflammation and has recently been proposed as a diagnostic biomarker of food allergy (FA) in children. The aim of this study was to compare FCP level in infants and children under 4 years old with 1) atopic dermatitis (AD) with food allergy (FA) and 2) children with AD and without FA with the results in healthy controls. In total, 46 infants and children (mean age 14 months ± 12) diagnosed with AD were divided into two groups: G1, children with atopic AD with FA (n=28) and G2, children with AD without FA (n=18). The control group (G3) was made up of healthy children of the same age (n=18). The median FCP was significantly higher in G1 compared with G2 (G1: median 154, IQR 416 µg/g vs G2: median 41.3, IQR 59 µg/g; P=0.0096). The median FCP in children with AD and FA was significantly higher before elimination diet in comparison with FCP after 3 months of elimination diet (median 154, IQR 416 µg/g vs median 35, IQR 23 µg/g; P=0.0039). The level of FCP was significantly positively correlated with the SCORAD score (r=0.5544, P=0.0022). Our study showed a significant difference in level of FCP in patients with AD without FA compared with patients with AD and FA. We also found a positive correlation of FCP with SCORAD score, a biomarker of AD severity. New studies are needed to investigate the role of FCP as a biomarker of FA in children with AD.

Reporting of activated partial thromboplastin time (aPTT): Could we achieve better comparability of the results?

INTRODUCTION: Activated partial thromboplastin time (aPTT) is determined and reported as clotting time in seconds aPTT(s), but it is presumed that reporting results as patient-to-normal clotting time ratio, aPTT(r), could minimize within-laboratory variability. The aim of study was to investigate differences in reporting aPTT results that can affect comparability of the results among Croatian laboratories and suggest further steps for its harmonization. MATERIALS AND METHODS: The questionnaire on aPTT reporting practice was distributed to 83 laboratories through Survey Monkey application in March 2019 as the part of the first regular round of Croatian Centre for Quality Assessment in Laboratory Medicine proficiency testing. RESULTS: The survey response rate was 0.49. Majority of laboratories report aPTT results as both, seconds and ratio. Participants reported use of 23 different aPTT(s) reference intervals along with 17 different combinations of reagent/coagulometer and 25 aPTT(s) denominators of different origin for aPTT(r) calculation. Despite the same aPTT(s) results, the use of different denominators caused a dispersion of aPTT(r) results that can lead to exceeding external quality assessment performance criteria of 7%, particularly when results were compared for the same reagent group only. By applying aPTT(s) reference interval mean as denominator for calculation of aPTT(r) reference interval better concordance to harmonized one was obtained (17 vs. 27; χ2 = 3.972; P = 0.046). CONCLUSION: In order to improve comparability of the results, laboratories are advised to use mean of aPTT(s) reference interval as denominator for aPTT(r) calculation. Type of coagulometer need to be considered when evaluating aPTT proficiency test results and its currently acceptable limit of performance evaluated accordingly.

Seroprevalence of SARS-CoV-2 infection among children in Children's Hospital Zagreb during the initial and second wave of COVID-19 pandemic in Croatia.

INTRODUCTION: The study aimed to investigate the prevalence and titres of anti-SARS-CoV-2 antibodies in children treated at the Children's Hospital Zagreb in the first and the second wave of the COVID-19 pandemic. Statistical significance of difference at two time points was done to determine how restrictive epidemiological measures and exposure of children to COVID-19 infection affect this prevalence in different age groups. MATERIALS AND METHODS: At the first time point (13th to 29th May 2020), 240 samples and in second time point (24th October to 23rd November 2020), 308 serum samples were tested for anti-SARS-CoV-2 antibodies by enzyme-linked immunosorbent assay (ELISA) and electrochemiluminescence immunoassay (ECLIA). Confirmation of results and titre determination was done using virus micro-neutralization test. Subjects were divided according to gender, age and epidemiological history. RESULTS: Seroprevalence of anti-SARS-CoV-2 antibodies differs significantly in two time points (P = 0.010). In first time point 2.9% of seropositive children were determined and in second time point 8.4%. Statistically significant difference (P = 0.007) of seroprevalence between two time points was found only in a group of children aged 11-19 years. At the first time point, all seropositive children were asymptomatic with titre < 8. At the second time point, 69.2% seropositive children were asymptomatic with titre ≥ 8. CONCLUSIONS: The prevalence of anti-SARS-CoV-2 antibodies was significantly lower at the first time point than at the second time point. Values of virus micro-neutralization test showed that low titre in asymptomatic children was not protective at the first time point but in second time point all seropositive children had protective titre of anti-SARS-CoV-2 antibodies.

Contraception-related deep venous thrombosis and pulmonary embolism in a 17-Year-old girl heterozygous for factor V leiden, prothrombin G20210A mutation, MTHFR C677T and homozygous for PAI-1 mutation: report of a family with multiple genetic risk factors and review of the literature.

We present the case of a 17-year-old girl who suddenly woke up with localized pain in the left groin and the inability to twist her leg. After comprehensive physician and laboratory examinations, deep venous thrombosis with consequent pulmonary embolism was ascertained. She had not experienced any recent trauma, but she had started to take oral contraceptives 6 months prior to the onset of the symptoms. Her parents and sisters had been asymptomatic throughout their lives, but the family history revealed a few thromboembolic accidents. Using DNA analysis, heterozygosity for factor V Leiden, prothrombin gene mutation G20210A and methylenetetrahydrofolate reductase C677T, as well as the homozygous 4G/4G genotype in the plasminogen activator inhibitor 1 were identified in our patient. Subsequently, DNA analysis was performed in all living family members, and multiple factors associated with thrombophilia were discovered. Our case confirms the multifactorial cause of thromboembolic events and emphasizes the importance of oral contraceptive use in the onset of venous thrombosis, especially in teenage females. In addition, this case indicates that teenage females with a family history of thrombosis who are making choices about contraception could most likely benefit from advanced thrombophilia testing.