Clinica chimica acta; international journal of clinical chemistry
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Comparative Study
Hydroxocobalamin and cyanocobalamin interference on co-oximetry based hemoglobin measurements.
Hydroxocobalamin (OHCbl) and cyanocobalamin (CNCbl) are dark-red colored analogs of vitamin B-12. OHCbl is used as an alternate antidote for cyanide poisoning. Due to the strong red color, if uncorrected, these cobalamins interfere with hemoglobin measurements and can introduce errors in spectrophotometric assay on co-oximeters. The impact of cobalamins on commonly used co-oximetry systems was compared to evaluate the accuracy of hemoglobin measurements and to further assess the ability of the instruments to detect and flag cobalamin interference. ⋯ Among the 4 co-oximeters tested in this evaluation, GEM Premier 4000 and Rapidpoint 405 analyzer showed minimal impact for hydroxocobalamin concentrations around 0.5 g/l. Cyanocobalamin displayed similar interference effect on co-oximetry measurements as OHCbl. The error detection system in the GEM Premier 4000 appropriately detected and flagged interferences on sample measurements.
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The development of highly sensitive cardiac troponin (cTnI) assays has increased the number of true and false positive results for patients suspected of acute myocardial infarction (AMI). Cases are reported whereby the use of serial testing, the 99th percentile cutoff, and the application of biological variation of cTnI were used to help determine ischemic vs. non-ischemic causes of myocardial injury. ⋯ Serial testing for troponin was useful in differentiating early AMI from non-ischemic causes of troponin increases. However, non-AMI patients with acute cardiac injury can produce troponin results that mimic AMI. Therefore serial troponin testing must be used in conjunction with clinical presentation and other laboratory findings.
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Preliminary studies report on significantly higher levels of the major cytoskeleton protein actin in CSF of patients with neurodegenerative conditions and that the dynamics of these levels obviously correlates with disease progression and clinical disability. One of the primary functions of actinfree Gc-Globulin is to bind and neutralize extracellular monomeric actin, released into the circulation by necrotic or ruptured cells, and thus ameliorating the clinical outcome in situations of severe organ damage. ⋯ In summary, our data propose a function of actinfree Gc-Globulin also in the clearance of actin filaments from CSF of patients with neuronal damage. However, active recruitment of hepatic derived actinfree Gc-Globulin to the site of CNS injury is not observed. Much more, BBB leakage enables extraneuronally synthesized actinfree Gc-Globulin to extent its scavenger capacity for actin also to the subarachnoidal space. Furthermore, intrathecal synthesis of actinfree Gc-Globulin seems to be increased in patients with severe neurodegeneration.
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An increased urinary albumin excretion (albuminuria) is an established test for the early detection of renal disease and is also recognized as a risk factor for cardiovascular disease and mortality in a number of clinical settings. There is an established body of data which shows that a random urinary albumin:creatinine ratio (ACR) based on a random urine sample correlates well with 24-hour urinary albumin excretion measurement. However, there is little data to show whether specific point-of-care testing devices can be used to rule-in or rule-out increased urinary albumin excretion in comparison to a 24-hour urinary albumin excretion measurement. ⋯ The CLINITEK system was shown to be a reliable test for ruling out increased urinary albumin excretion with negative likelihood ratios less than 0.05 above the 24-hour urinary albumin excretion rate of 30 mg/24 h (threshold for microalbuminuria), and less than 0.01 above the albumin excretion rate of 100 mg/24 h. The DCA 2000+ system demonstrated similar performance as a rule-out test, with likelihood ratios of less than 0.02 at 24-hour albumin excretion rates above 30 mg/24 h. Both the CLINITEK and DCA 2000+ systems could be used to rule-out increased urinary albumin excretion at the albumin excretion cut-off rate of 30 mg/24 h in this cohort of patients.