Prevention of interference by dextran with biuret-type assay of serum proteins

Interference by piperacillin/tazobactam in the measurement of creatinine with the Jaffe method and of total protein with the biuret method

Serum creatinine and total protein are routinely measured biochemical parameters used in clinical medicine. An abnormal result caused by interference with the assay does not accurately reflect a patient's clinical state and therefore risks misleading clinicians. We report the case of a patient who had unexplainable high creatinine and total protein results. The blood collection was contaminated with intravenous fluid and the patient was receiving piperacillin/tazobactam. Additional laboratory studies demonstrated piperacillin/tazobactam was the cause of the false positive results and the elevation in both serum creatinine and protein level was dependent on the concentration of antibiotic present.

Management of electrolyte disorders: also the method matters!

Introduction: For the last few decades, electrolyte determinations in plasma or serum are carried out by reliable potentiometric methods. In recent years, a marked technical evolution has taken place, where the clinical analysis of common analytes (e.g. electrolytes) is partly moving from centralised clinical core laboratories to near-patient point-of-care testing. Methods: As the measuring principle used by point-of-care testing markedly differs from the one used in core laboratories, sodium results are not always interchangeable in critically ill patients due to the different sensitivity of the analytical methods for the electrolyte exclusion effect. Results: This effect mainly occurs in patients with decreased plasma protein values. The observed differences in generated test results might significantly affect the judgment and the treatment of electrolyte disturbances. As technical solutions are not likely to occur in the near future, clinicians and laboratorians should be well aware of this growing problem. Mathematical correction of the sodium results for plasma protein concentration may resolve the problem to a certain extent. Discussion: Although electrolyte determinations are generally very reliable, analytical interferences can occur for sodium rarely, mainly due to contamination by surfactants, benzalkonium in particular. For potassium, the major problem is hemolysis. To a lesser extent, leukocyte lysis and thrombocytopenia may also interfere. For chloride determination, the selectivity of the electrodes used is not ideal. Occasionally, false positive signals can be observed in presence of interfering ions (e.g. bromide).

Evaluation of oxidant-antioxidant status in overweight and morbidly obese Saudi children

AIM: To evaluate the antioxidant enzymes and oxidative products in overweight and obese Saudi children before the onset of metabolic complications.

METHODS: The study was carried out on 231 Saudi children. They were classified into three groups: uncomplicated overweight, uncomplicated morbid obesity, and the matched age group as control. All subjects underwent anthropometric measurements and activities of superoxide dismutase, catalase, glutathione peroxidase (GSH-Px), glutathione reductase, the concentrations of reduced GSH, malondialdehyde (MDA) oxidized low-density lipoprotein (ox-LDL) and advanced oxidation protein products (AOPPs) were measured in the blood of these groups.

RESULTS: Overweight and obese children had a significantly higher body mass index, while obese children only had a significantly higher waist-to-hip ratio compared to that of the control group. The enzyme activities under study were significantly elevated in the overweight group, although they were significantly reduced among obese children. The concentration of GSH was reduced in both the overweight and obese groups. The mean values of ox-LDL, MDA and AOPP were non-significantly increased in overweight children, while they were significantly elevated in obese children compared to that of normal weight children. A significant disturbance of oxidant-antioxidant status was observed in severely morbid children.

CONCLUSION: The increase of oxidative stress in obese children is associated with the increase in AOPPs and MDA which reflects an imbalance between reactive oxygen species production and antioxidant defense.