Lipemia: causes, interference mechanisms, detection and management

In the clinical laboratory setting, interferences can be a significant source of laboratory errors with potential to cause serious harm for the patient. After hemolysis, lipemia is the most frequent endogenous interference that can influence results of various laboratory methods by several mechanisms. The most common preanalytical cause of lipemic samples is inadequate time of blood sampling after the meal or parenteral administration of synthetic lipid emulsions. Although the best way of detecting the degree of lipemia is measuring lipemic index on analytical platforms, laboratory experts should be aware of its problems, like false positive results and lack of standardization between manufacturers. Unlike for other interferences, lipemia can be removed and measurement can be done in a clear sample. However, a protocol for removing lipids from the sample has to be chosen carefully, since it is dependent on the analytes that have to be determined. Investigation of lipemia interference is an obligation of manufacturers of laboratory reagents; however, several literature findings report lack of verification of the declared data. Moreover, the acceptance criteria currently used by the most manufacturers are not based on biological variation and need to be revised. Written procedures for detection of lipemia, removing lipemia interference and reporting results from lipemic samples should be available to laboratory staff in order to standardize the procedure, reduce errors and increase patient safety

Hemolysis detection and management of hemolyzed specimens

Assay interferences have long been underestimated and unfortunately too often undetected in the daily clinical laboratory practice. The extra-analytical phase of the laboratory testing process has been recognized as the major source of laboratory errors over the past decade. Preanalytical errors are most common errors within the total testing process and hemolysis is recognized as one of the most prevalent preanalytical errors and surely the most prevalent interference in clinical laboratory testing. Visual detection of hemolysis is arbitrary and therefore mostly unreliable since it may over- and underestimate the actual prevalence of hemolyzed serum specimens (i.e., trained observers are unable to accurately rank the degree of interference in serum). Elevated concentration of bilirubin may further impair the ability to detect hemolysis by visual inspection and therefore lead to serious underestimation of hemolysis in neonatal samples where elevated bilirubin concentration is commonplace. The recent advances in laboratory technology have lead to an increasing trend in the automation of various preanalytical processes into large preanalytical modules. Such modules as well as novel automated laboratory analyzers offer the automated detection of serum indices. This is advantageous due to the increased reproducibility and the improvement in detection of mildly hemolyzed specimens (serum hemoglobin < 0.6 g/L). These platforms commonly use the semiquantitative spectrophotometric measurement and grade interfering substances into several categories. However, various analytical platforms may have different decision thresholds for various serum indices. Moreover, different systems might be different in their assay parameters and the degree of the interference of the specific interfering substance. Therefore, more efforts should be focused to standardize the mean of reporting the hemolysis index, especially when this important parameter is used for obtaining meaningful information on the quality of sample collection throughout collection centers and wards. Hemolysis is still one of the biggest challenges to the laboratory specialists. In case of hemolysis, laboratory personnel should always ask for new sample(s). In case new sample(s) can not be obtained, it is the responsibility of the laboratory specialist to communicate the problem with the physician responsible for the patient and seek for the solution to the best of the patient care

Preanalytical external quality assessment of the Croatian Society of Medical Biochemistry and Laboratory Medicine and CROQALM: finding undetected weak spots

Introduction: The aim of this paper is to present results of first two years of preanalytical external quality assessment (EQA) in Croatia. Materials and methods: This paper summarizes results from 6 rounds of preanalytical EQA during 2014-2016 in 161-175 Croatian laboratories (number ranged between cycles). EQA was designed as an online survey of the compliance with National recommendations for phlebotomy (NRP). Forty-seven questions in 5 categories are analyzed (materials and equipment, patient identification, patient preparation, sampling and storage). Additionally, preanalytical cases are presented. Overall performance scores (Question score (Qscore) for compliance with NRP and Case score (Cscore) for preanalytical cases) are calculated for each question/case as a proportion of laboratories with satisfactory procedure (x 100). Qscores and Cscores ? 70 were classified as acceptable (maximal score = 100). Results: In investigation of compliance with NRP, acceptable Qscores were obtained for 34/47 questions. The lowest scores were observed for the availability of sterile disposable tourniquets (Qscore = 15) and safe-sharp needles (Qscore = 34), obtaining patients address as an identifier (Qscore = 21), using glycolysis inhibitor tubes for glucose concentration measurement (Qscore = 21) and verification of manufacturers declarations on temperature and time of storage (Qscore = 31). There was no statistically significant difference in overall Qscore according to different categories of phlebotomy procedures (P = 0.284). The results of preanalytical cases showed acceptable Cscore values for all cases (89-96). Conclusion: First two years of preanalytical EQA showed good compliance with the NRP and excellent expertise in resolving complex preanalytical issues. Major critical spots are lack of availability of safe-sharp needles, disposable tourniquets and glucose inhibitor tubes

Preanalytics of urine sediment examination: effect of relative centrifugal force, tube type, volume of sample and supernatant removal

Introduction: Laboratories often modify procedures recommended by the European Urinalysis Guidelines for urine sediment analysis. The aim of this study was to compare the recommended protocol with our routine laboratory procedure and to evaluate the possible impact of modifications in the relative centrifugal force, type of tube, method of supernatant aspiration and urine volume on patient’s results. Material and methods: Firstly, relative centrifugal force was investigated using 20 pairs of samples examined after centrifugation at 400xg and 1358xg. In phase two, 110 samples were examined, paired as: round bottom vs conical tube (N = 46), decanting vs suction of supernatant (N = 100) and 10 mL vs 5 mL of urine sample (N = 101). Results: The number of erythrocytes, leukocytes and squamous epithelial cells was significantly lower after centrifugation at 400xg (P = 0.001, 0.002 and 0.004, respectively). The number of leukocytes was significantly lower in conical tubes (P = 0.010), after the suction of supernatant (P = 0.045) and in 5 mL urine (P < 0.001). The number of squamous epithelial cells was significantly lower after the suction of supernatant (P < 0.001) and in 5 mL urine (P < 0.001). The number of erythrocytes (P < 0.001), total non-hyaline casts (P < 0.001) and the frequency of granular casts (P = 0.039) was significantly lower in 5 mL urine. Conclusion: Lower results of leukocytes, erythrocytes, squamous cells and non-hyaline casts were recorded in recommended procedures (centrifugation at 400xg, suction of supernatant, conical tube, 5 mL of sample) than in routine procedure (centrifugation at 1358xg, decanting of supernatant, round bottom tube, 10 mL) used in our laboratory

Statistical errors in manuscripts submitted to Biochemia Medica journal

Uvod: Neispravna uporaba statističkih metoda može biti uzrokom iskrivljenja rezultata, netočnih zaključaka i znatnog gubitka financijskih i drugih sredstava i kao takva se smatra vrlo neetičnom. Nažalost, velik broj objavljenih radova u medicinskim časopisima sadrži neke statističke pogreške. Cilj ovog rada bio je utvrditi učestalost nekih najčešćih statističkih pogrešaka, u člancima zaprimljenih u uredništvo časopisa Biochemia Medica, tijekom četverogodišnjeg perioda, u razdoblju od 2006. do 2009. godine. Materijali i metode: Obuhvaćeni su svi izvorni znanstveni i stručni radovi, koji su sadržavali statističku analizu podataka, zaprimljeni u uredništvo časopisa Biochemia Medica u razdoblju od 2006. do 2009. godine. Rukopisi su pregledani od strane dva recenzenta. Sljedeće pogreške su uključene u analizu: 1) pogrešna uporaba ili prikaz deskriptivne analize; 2) pogrešan izbor statističkog testa; 3) pogrešna uporaba statističkog testa za usporedbu tri ili više skupina; 4) pogrešan prikaz P vrijednosti; 5) pogrešno tumačenje P vrijednosti; 6) pogrešno tumačenje rezultata korelacije; 7) nije provedena analiza snage istraživanja. Rezultati: Ukupno je obuhvaćeno 55 rukopisa. Niti jedan od rukopisa nije imao provedenu analizu snage istraživanja. Od ostalih šest pogrešaka, barem jedna pogreška utvrđena je u 48/55 (0,87) rukopisa. Najučestalije pogreške su bile neispravna uporaba statističkog testa za usporedbu tri ili više skupina (21/28 (0,75) članaka) i neispravan prikaz P vrijednosti (36/54 (0,66) članaka). Zaključak: Statističke pogreške su vrlo učestale u ruko pisima zaprimljenim u uredništvo časopisa Biochemia Medica. Sve potencijalne pogreške ustanovljene tijekom recenzije od strane statističkog recenzenta bile su ispravljene prije objavljivanja članaka, što je značajno unaprijedilo njihovu kvalitetu.Introduction: The inappropriate use of statistical methods may lead to distorted results, incorrect conclusions, and substantial waste of financial and other resources and is considered highly unethical. Unfortunately, a great number of published medical research contain some statistical errors. The aim of this study was to assess the frequency of several most common statistical errors, in manuscripts submitted to Biochemia Medica journal for possible publication, during the 4 year period, since 2006-2009. Materials and methods: All original scienti2c and professional manuscripts submitted to Biochemia Medica during the 2006-2009 were eligible for the study, if they contained some kind of statistical analysis of the data. Manuscripts were reviewed manually by two reviewers. Following errors were included: 1) incorrect use or presentation of descriptive analysis; 2) incorrect choice of the statistical test; 3) incorrect use of statistical test for comparing three or more groups for differences; 4) incorrect presentation of P value; 5) incorrect interpretation of P value; 6) incorrect interpretation of correlation analysis; 7) power analysis not provided. Results: A total of 55 eligible manuscripts were identified. None of these manuscripts reported power analysis. As of other 6 errors analyzed, at least one error was observed in 48/55 (0.87) manuscripts. Most common errors were incorrect use of statistical test for comparing three or more groups for differences (21/28 (0.75)) and incorrect presentation of P value (36/54 (0.66)). Conclusion: The statistical errors are highly prevalent in manuscripts submitted to Biochemia Medica. All errors identified by statistical reviewer during the review process were successfully corrected prior to publication, what has greatly improved the overall quality of the manuscript

Analytical validation of therapeutic drug monitoring (TDM) on AxSYM Abbott analyzer

Introduction: Careful monitoring of drug concentration (therapeutic drug monitoring, TDM) is essential for a large number of drugs. The aim of this study was to evaluate analytical performance of Abbott AxSYM analyzer for therapeutic drug monitoring of theophylline, carbamazepine, pheno-barbital and valproic acid. Materials and methods: For the purpose of analytical validation following parameters were determined for all analytes: inaccuracy (bias), within-run and between-run imprecision and measurement uncertainty. Additionally, concentration of valproic acid was compared with the previously used analytical system (TDx FLx Abbott analyzer) for 30 patients\u27 samples. Results: Inaccuracy results (bias) were as follows: for theophylline from -3.66% to -5.84%; for carbamazepine -0.46% to 1.00%; for phenobarbital -1.83% to -8.08% and for valproic acid from -1.01% to -5.65%. The highest coefficient of variation (CV) for within run imprecision was observed for phenobarbital (7.07%) and the lowest for theophylline (2.71%). The highest CV for between run imprecision was observed for carbamazepine (4.73%) and the lowest for theophylline (2.94%). The highest measurement uncertainty was observed for phenobarbital assay (21.7%) and the lowest for carbamazepine (10.7%). Passing-Bablock regression analysis of valproic acid comparison on two analyzers showed statistically significant, but clinically insignificant deviation in slope of the regression equation (b = 1.121; 95% CI = 1.028-1.197); however the Cusum linearity test proved that there was a linear relationship between two methods. Conclusion: In conclusion, analytical validation fulfilled all previously established criteria and could be implemented in a routine laboratory work

The Association of Uric Acid with Glucose and Lipids in General Population: Croatian Cross-Sectional Study

Hyperuricemia may have an important role in metabolic syndrome, cardiovascular diseases and stroke. Elevated serum uric acid concentration has been shown to be the strong predictor of cardiovascular mortality in several recently published studies. Our aim was to determine the prevalence of hyperuricemia in general Croatian population and to investigate the association of serum uric acid with glucose and lipids. This was a retrospective cross-sectional study on 6,476 consecutive adults. Prevalence of hyperuricemia was 13.9% in general population and it was significantly higher in males, than in females (26% vs. 6%; p<0.001). Median uric acid concentration was higher in males than in females (343 vs. 238 mmol/L; p<0.001). Age, glucose and lipid parameters did not correlate with uric acid. In hyperuricemic subjects, increased concentrations of glucose (33.1% vs. 13.1%; p<0.001), triglycerides (46.9% vs. 17.6%; p<0.001), total cholesterol (69.6% vs. 51.9%; p<0.001), LDL-cholesterol (64.5% vs. 46.4%; p<0.001) and decreased concentration of HDL- -cholesterol (24.3% vs. 13.0%; p<0.001) were more prevalent than in subjects with normal serum concentrations of uric acid. Hyperuricemia is highly prevalent in Croatian general population and it aggregates with hyperglycemia and dyslipidemia

Frequency of factor II G20210A, factor V Leiden, MTHFR C677T and PAI-1 5G/4G polymorphism in patients with venous thromboembolism: Croatian case-control study

Introduction: Venous thromboembolic disease is one of the leading causes of morbidity and mortality in the developed world. Identification of hereditary factors of thrombophilia is contributing to a better understanding of the etiology and disease prevention. The aim of this study was to assess the prevalence of factor IIG20210A, factor V Leiden, MTHFR (methylenetetrahydrofolate reductase) C677T and PAI-1 (plasminogen activator inhibitor-1) 5G/4G polymorphisms in healthy Croatian subjects and patients with thromboembolism. Materials and methods: This prospective study included 100 thromboembolic patients consecutively admitted to the Intensive Care Unit, Sestre Milosrdnice University Hospital and 106 healthy subjects. Genotyping of factor IIG20210A, factor V Leiden, MTHFR C677T and PAI-1 5G/4G polymorphisms was done using melting curve analysis on Light Cycler 1.2 analyzer. Results: Heterozygotes for Factor V Leiden polymorphism were more frequent in the group of patients with the thromboembolic disease (16%) than in the control healthy subjects (2.9%), OR (95% CI) = 6.41 (1.81-22.8); P = 0.004. Allele and genotype frequencies of other studied polymorphisms did not differ between cases and controls. Conclusion: This study confirmed the association of factor V Leiden polymorphism with the thromboembolic disease in Croatian population