Multi-site, multi-country evaluation of analytical and operational performance of a low-mid volume chemiluminescent immunoassay analyzer.

BACKGROUND: A new automated immunoassay low-mid volume (< or = 250 immunoassays/day) chemiluminescent analyzer, Abbott Architect i1000sR, was evaluated by seven laboratories around the world (4 in Europe, one each in Canada, Japan, and the U.S.A.) to demonstrate equivalent performance for key operating characteristics (e.g., precision, turn around time, limit of detection, functional sensitivity, and linearity). METHODS: The laboratories followed standard protocols to assess precision, limit of detection (LoD), functional sensitivity, assay linearity, method comparison, and sample carryover. Turn around time for three stat assays (beta-hCG, BNP, and CK-MB) and the time required to complete workloads of 50 and 100 tests with a mixture of 75% routine tests and 25% stat tests was also evaluated. RESULTS: Total precision was typically < 5% CV for nine immunoassays. Analytical performance met design goals and demonstrated equivalency to package insert data for assays on market and in use for an existing high volume immunoassay system. Stat turn around times were consistent with the fixed analytical time of 15.6 minutes and met the expectations of the laboratories. Measured test throughput ranged from 47 - 54 tests per hour and demonstrated that the analyzer was fit for the intended purpose of supporting a laboratory that performs < or = 250 immunoassays per day. CONCLUSIONS: A multisite, international analyzer familiarization study is a practical means of confirming that a new instrument meets both a manufacturer's design specifications and users' real world expectations and provides a pragmatic test for the system. The experience of investigators at seven sites around the world indicates that a new fully automated chemiluminescent system is suitable for use.

Pseudoplatelets: a retrospective study of their incidence and interference with platelet counting.

AIMS: Spurious platelet counts can be found in acute leukaemias, as a result of the fragmentation of blood cells. Microscopic examination of a blood smear should be performed to detect the presence of these so called pseudoplatelets. When present, the platelet count should be corrected because of the important clinical consequences that a lower platelet count may have in these patients. METHODS: K(3)EDTA anticoagulated blood was measured on an automated blood cell counter, and a blood smear was made and stained according the May Grünwald-Giemsa method for microscopic observation. A 500 cell/particle differentiation was performed and the automated platelet count was corrected. RESULTS: The incidence of pseudoplatelets in 169 patients with acute leukaemia was studied. Pseudoplatelets were detected in 43 patients (25.4%), and seven patients (4.1%) were re-classified as having a major bleeding risk (platelet count, < 15 x 10(9)/litre). CONCLUSIONS: Platelets should be determined morphologically in patients with acute leukaemia and a routine screening method for the detection of pseudoplatelets should be developed.

Capillary blood gas analysis in complex regional pain syndrome: a pilot study.

BACKGROUND: The pathophysiology of complex regional pain syndrome type 1 (CRPS 1) is still a matter of debate. An inflammatory reaction may cause the syndrome. Increasing evidence points to a role for impairment of oxygen metabolism in the affected limb. METHODS: In this pilot study (16 patients) we performed capillary blood gas analysis in extremities with acute CRPS 1, in order to assess oxygen saturation and lactate concentrations. Comparison was made with the unaffected limb for capillary blood pH, pO(2), SaO(2), and lactate and glucose concentrations. RESULTS: No statistically significant differences could be found. CONCLUSIONS: Capillary blood gas analysis is not useful to detect changes in oxygen saturation and lactate concentrations in CRPS 1.

Pseudothrombocytopenia: a report of a new method to count platelets in a patient with EDTA- and temperature-independent antibodies of the IgM type.

Pseudothrombocytopenia is usually associated with blood specimens anticoagulated with ethylenediamine tetraacetic acid (EDTA) or other anticoagulants. It may be caused by temperature-independent, EDTA-dependent antibodies of the immunoglobulin-M (IgM) type. Here a patient with EDTA-independent and temperature-independent pseudothrombocytopenia mediated by IgM or IgM-containing immune complex is reported, and a reliable method is described for a proper counting of platelets in such cases.

Automated counting of nucleated red blood cells in blood samples of newborns.

Nucleated red blood cells (NRBC) in blood samples interfere with the white blood cell (WBC) count on many types of automated haematology analysers. This makes it necessary to correct the WBC count by counting NRBC microscopically. This report describes the evaluation of two analysers, the Cell-Dyn 4000 and the Sysmex XE-2100, which use new techniques to recognize and enumerate NRBC. We conclude that both the Cell-Dyn 4000 and the Sysmex XE-2100 give an accurate WBC count in the presence of NRBC. Furthermore, they can enumerate NRBC correctly when compared with microscopic observation.

Bacteria in blood smears: overwhelming sepsis or trivial contamination.

It is unusual to find microorganisms in peripheral blood smears, and their presence is frequently associated with overwhelming sepsis and consequently a poor prognosis. In this report, we demonstrate 4 cases with bacteria in blood smears. Two of them had a fatal outcome, but the other 2 were caused by a contamination either via the central venous catheter or in vitro, both without dramatic outcome. The finding of bacteria in blood smears has to be interpreted carefully, and thorough examination of peripheral blood smears may be of great importance in the early diagnosis of bacteremia; however, in vitro contamination must be excluded.

Peripheral blood lymphocyte appearance in a case of I cell disease.

In general, peripheral blood smears are performed to obtain information with regard to various morphological features as an aid in the diagnosis of infection or malignancy. This report presents a patient with I cell disease (inclusion cell disease), a fatal lysosomal storage disorder caused by a defect in an enzyme responsible for the transfer of mannose-6-phosphate ligands to precursor lysosomal enzymes. As a consequence, most lysosomal enzymes are transported outside the cell instead of being correctly targeted into the lysosomes, resulting in the storage of macromolecules in lysosomes. I cell disease, with its heterogeneous clinical presentation, can be diagnosed by the presence of intracellular vacuole-like inclusions in lymphocytes and fibroblasts, high serum lysosomal enzyme activities, and a defect of N-acetylglucosamine-1-phosphotransferase. This report describes the morphological aspects of peripheral lymphocytes in a blood smear of a patient, the first clue to the final diagnosis of I cell disease. The observed vacuole-like inclusions in lymphocytes of this patient were negative for periodic acid Schiff (PAS) and Sudan black B staining, in contrast to earlier reports.

Point mutation in the stalk of angiotensin-converting enzyme causes a dramatic increase in serum angiotensin-converting enzyme but no cardiovascular disease.

BACKGROUND: Angiotensin-converting enzyme (ACE) metabolizes many small peptides and plays a key role in blood pressure regulation. Elevated serum ACE is claimed to be associated with an increased risk for cardiovascular disease. Previously, two families with dramatically increased serum ACE were described, but no systematic survey of affected individuals was performed, and the molecular background of this trait is unknown. METHODS AND RESULTS: Eight families were identified with autosomal dominant inheritance of a dramatic (5-fold) increase of serum ACE activity. Strikingly, no clinical abnormalities were apparent in the affected subjects. Isolated blood cells were used for genetic and biochemical analysis. The level of ACE expression on the blood leukocytes and dendritic cells and total cell-associated ACE of the affected individuals was similar to that in nonaffected relatives; however membrane-bound mutant ACE was much more efficiently clipped from the cell surface compared with its wild-type counterpart. A point mutation causing Pro1199Leu in the stalk region of the ACE molecule cosegregates with the increase in serum ACE (LOD score, 6.63). CONCLUSIONS: A point mutation in the stalk region of the ACE protein causes increased shedding, leading to increased serum ACE, whereas cell-bound ACE is unaltered, and affected individuals exhibit no clinical abnormalities. These findings qualify the importance of serum ACE and establish a new determinant of ACE solubilization.

Infusion of plasma expanders may lead to unexpected results in urinary protein assays.

Overt proteinuria was detected in the urine of a potential kidney donor, ultimately leading to the refusal of the kidneys for transplantation purposes. Histological examination of the kidneys did not reveal any abnormalities. Searching for substances that could have interfered with the urinary total protein assay, the role of infused, modified gelatin plasma expanders was investigated. We therefore measured the concentration of protein before and after the addition of various artificial plasma expanders to urine. Only when Biuret reagent or Pyrogallol Red dye were used did we find elevated concentrations of protein. Other methods, including the turbidimetric assays, did not detect additional amounts of protein in the spiked urine. We conclude that the infusion of modified gelatin solutions may cause apparent proteinuria. This effect is not observed with starch-based plasma expanders. Clinical chemists and clinicians should be aware of this phenomenon and possibly repeat the analysis with a different technique.

Evaluation of five different high-density lipoprotein cholesterol assays: the most precise are not the most accurate.

We evaluated the accuracy and performance of four different test kits for the direct determination of high-density lipoprotein (HDL)-cholesterol and compared them with the phosphotungstic acid/MgCl2 assay. All four homogeneous assays were precise (within-run CV of < 2.0% and between-run CV of < 6.4%); both assays based on immuno-inhibition had the lowest CVs (within-run 1.3% and 0.9%; between-run 2.3% and 2.2%). Interference from haemolysis was negligible, but triglyceride concentrations gave a negative interference. The effects of conjugated and unconjugated bilirubin were opposite; conjugated bilirubin showed a negative interference of up to 40%; unconjugated bilirubin interfered positively up to 50%. Using the recently validated indirect phosphotungstic acid/MgCl2 method as a comparison, all four homogeneous assays did not fulfil the National Cholesterol Education Program total error standard, mainly due to the positive biases of 12 to 42%, apparently associated with improper calibrators. Both assays involving immuno-inhibition showed a concentration-dependent bias.

[The magnitude of the 'anion gap']. / De grootte van de 'anion gap'.

The anion gap is used to evaluate disturbances in the acid-base balance, in particular metabolic acidosis. Due to the introduction of new clinical chemical techniques and modern analysers the reference range of the anion gap has changed. Clinical chemical laboratories should establish or verify their own anion gap reference range. Better communication between the laboratory and the clinician with regard to the anion gap is desirable.

Evaluation of a biosensor for the measurement of lactate in whole blood.

OBJECTIVES: Evaluation of the analytical performance of a biosensor for the measurement of lactate in whole blood samples and comparison of the results of patients samples with a routinely used spectrophotometric enzymatic method. DESIGN AND METHODS: Heparinized whole blood samples of patients and aqueous control samples were used to determine precision and carry-over. For comparison of the lactate biosensor and the enzymatic method human blood samples were split and measured. RESULTS: Satisfactory within-run (n = 7) and day-to-day (n = 15) precision was found, while carry-over was minimal (<0.2%). A statistically significant relation between the lactate levels in whole blood samples (n = 31) and the corresponding plasma samples was found: y = 0.98x - 0.05 and r = 1.00. No correlation was found between the hematocrit (range 0.23-0.51) and the difference in lactate concentration between plasma and whole blood. When comparing patient results (n = 722) obtained with the spectrophotometric method and the biosensor method, the biosensor measured 13% higher lactate levels. A correction on the basis of the hematocrit minimized this difference. CONCLUSION: The combination of analytical performance, easy handling, rapid analysis, and measurement in whole blood makes the biosensor suitable for lactate STAT-analyses. Care must be given to the interpretation of the results as well as to the preanalytical aspects.

Rapid and reliable measurement of highly elevated blood ammonia concentrations in children.

Newborns and children may suffer from extremely high ammonia levels in their blood. We evaluated a fast, reliable micromethod, based on the Blood Ammonia Checker II (BAC II) in combination with the dilution with fresh whole blood. Comparison of the proposed method with an enzymatic method revealed a statistically significant correlation. We conclude that the dilution of patient's blood with fresh whole blood extends the measuring range of ammonia on the BAC II analyzer from 286 mumol/l to about 700 mumol/l.

Pathogenesis of glomerular injury in the fawn-hooded rat: effect of unilateral nephrectomy.

Fawn-hooded (FH) rats with congenital proteinuria and systemic and glomerular hypertension are very susceptible to renal damage at a young age. In this study, the effects of unilateral nephrectomy (UNX) on the function and structure of the remaining kidney in the FHH substrain were assessed. A long-term study was performed to determine the changes in systemic blood pressure, renal function, and proteinuria during the development of chronic renal failure in UNX-FHH and two-kidney (2K) FHH rats. Renal micropuncture and morphologic studies were performed at 4 wk after surgery. The long-term study showed that, after UNX, systolic blood pressure did not differ significantly (from that of 2K-FHH rats. After UNX, there was compensatory hyperfiltration, at about 70% of the 2K level, that could be maintained for 12 wk only. The subsequent fall in GFR was preceded by severe proteinuria. The mean survival time of UNX-FHH rats was only 35 wk. Micropuncture studies showed that the high mean glomerular capillary pressure of 2K-FHH rats was further elevated after UNX. The glomerular capillary ultrafiltration coefficient did not differ significantly between UNX-FHH and 2K-FHH rats. The weight of the remaining kidney and the mean glomerular tuft volume in UNX-FHH were, on average, 36 and 31% greater than in 2K rats. The results indicate that the FHH rat is extremely vulnerable to the adverse renal effects of UNX.(ABSTRACT TRUNCATED AT 250 WORDS)