Third-party verification of total and specific immunoglobulin E on analyzer Immulite® 2000XPi.

BACKGROUND: Although Immulite®2000XPi (Siemens) allergy testing is routinely used in laboratories worldwide; a well-designed comprehensive third-party verification of its analytical performance has not yet been published. Our aim was to verify stability, precision and reference intervals for total and some frequent specific IgEs, test trueness for several most common allergens and assess the comparability of fluorescent- and chemiluminescent-enzyme immunoassay for total IgE. METHODS: Verification was based on EP15-A3, EP9-A3 and EP28-A3c CLSI guidelines. Stability was tested on serum pools stored at 2-8 °C, during 7 days. Manufacturer's reference intervals were verified for children and adults. Acceptance criteria were based on manufacturer specifications and national External Quality Assessment provider data. RESULTS: Samples for total IgE analysis were stable at 2-8 °C for 7 days. Precision was within manufacturer's specifications for most of tested allergens, except for total IgE (92.5 kIU/L, CVs 5.6% and 7.6%) and w1 (9.3 kU/L, CV = 5.9%). Bland-Altman plot revealed statistically significant constant (-32.4 kIU/L) and proportional bias (-20.2%) for total IgE between two methods. Passing Bablok showed statistically but not clinically significant biases between two Immulite analyzers for betula verrucosa (constant and proportional), house dust mite and egg white allergens (proportional). For adults and children, total IgE results were within reference intervals declared by Siemens. CONCLUSIONS: Immulite®2000XPi assay has acceptable precision and trueness. Samples for total IgE are stable even longer than declared by the manufacturer. Declared reference intervals can safely be adopted for both adult and children population in our laboratory. Fluorescent- and chemiluminescent-enzyme immunoassay results of total IgE are not comparable.

Effect of different pre-analytical conditions on plasma lactate concentration.

INTRODUCTION: Plasma lactate is a frequently used and important parameter for medical decision making. To setup a pre-analytical algorithm, we aimed to investigate the influence of different test tube additives, aliquoting, ice storage and haemolysis on plasma lactate concentrations for possible sparing critically ill (ICU) patients of additional blood drawing. MATERIALS AND METHODS: In our study (N = 177), lactate concentration and haemolysis index (HI) were measured in aliquoted (AHP) and unaliquoted (HP) Li-heparin, NaF/K3EDTA and NaF/KOX plasma, centrifuged within 15 minutes after venipuncture, on Cobas c501 analyzer. Differences were tested using the Wilcoxon's test and Passing-Bablok regression. Clinical accuracy of results was assessed in 107 ICU patients based on reference interval and clinical decision limits. RESULTS: Lactate concentrations did not differ in NaF/K3EDTA and NaF/KOX plasma (P = 0.855). No clinically significant difference of AHP compared to NaF/K3EDTA lactate was found (y = 0.13 (0.08 to 0.19) + 1.02 (0.99 to 1.08) x) if samples were aliquoted within 30 minutes after venipuncture. On contrary, lactate concentrations in HP showed significant proportional difference (y = 0.07 (- 0.12 to 1.24) + 1.37 (1.22 to 1.56) x) and were clinically incorrect in 14% of patients. Transport in ice bath increases HI in NaF/K3EDTA (P < 0.001), but without influencing lactate results compared to room temperature (y = 0.03 (- 0.06 to 1.00) + 1.05 (0.99 to 1.11) x). CONCLUSIONS: Lactate determination in HP is unacceptable because of high proportional error and high risk of clinical inaccuracy compared to NaF/K3EDTA. If pre-analytical conditions are met, AHP, NaF/K3EDTA and NaF/KOX plasma can be used interchangeably. Aliquoted Li-heparin samples alow measurement of other biochemical tests from a single tube and can spare ICU patients from additional blood drawing. Storage in ice bath provides no additional stabilization in NaF/K3EDTA tubes.

Changing the electronic request form proves to be an effective tool for optimizing laboratory test utilization in the emergency department.

OBJECTIVES: Appropriate laboratory utilization more often than not needs to be initiated by the laboratory. This study was performed to analyze the impact on test ordering patterns in the emergency department obtained by omitting certain tests from the electronic tick box request form. The tests could still be ordered by writing the full name of the test or by a phone call. METHODS: Erythrocyte sedimentation rate (ESR), fibrinogen, aspartate aminotransferase (AST), calcium and lipase were omitted from the electronic request form and could subsequently be ordered either by phone or a typed-in request. A reflex testing protocol was elaborated for reduction of creatine kinase (CK) and CK-MB analyses. All interventions were introduced with prior consultation with clinical staff and according to current guidelines. The reduction of test orders and costs in the post-intervention period was assessed. All data were retrieved retrospectively from the laboratory information system (LIS). RESULTS: Disappearance from the tick box request form resulted in a significant decrease in the number of requests for targeted tests in the post-intervention year, mostly affecting AST and fibrinogen (83% and 79% reduction of ordering, respectively), followed by a 58% reduction in calcium orders, and 54% and 43% reductions in ESR and lipase requests, respectively. A substantial reduction in CK requests was also observed, while CK-MB requests almost disappeared. Annual cost savings that emerged from all implemented interventions were estimated to be 19,445€. CONCLUSION: Significant reduction in ordering of selected tests was achieved simply by limiting their availability in hospital computerized order entry (COE) system. The present data suggest that removal of laboratory tests from the electronic request form can be an effective tool for changing physicians' test ordering behavior.

Advances and Pitfalls in Using Laboratory Biomarkers for the Diagnosis and Management of Sepsis.

Sepsis is a critical patient condition with high mortality rate caused by a complex and inadequate host response to infection. Since early identification and start of antibiotic therapy in the first few hours after sepsis development dramatically improves outcomes, it is of utter importance to offer fast, reliable and specific early laboratory biomarkers to help clinicians in sepsis recognition. On the other hand, the biomarkers should also be helpful in excluding sepsis and/or confirming therapy effectiveness, and thus prevent overprescribing of antibiotics. In this paper, we discuss the significance and relative merits of three currently available protein biomarkers: C-reactive protein, procalcitonin and presepsin. Although useful, none of these biomarkers has been shown to completely fulfill the roles mentioned above.