Visual assessment of hemolysis affects patient safety.

BACKGROUND: Manual handling of hemolyzed samples is not standardized and is vulnerable to errors. This study aimed to evaluate laboratory errors due to manual handling of hemolyzed samples and to assess the risk they might have for patient safety. METHODS: Data were retrospectively obtained from a laboratory information system for 25 emergency tests from hemolyzed samples. Hemolysis (concentration of free hemoglobin >0.5 g/L) was visually assessed by comparison with a color chart. The reference person reestimated the routinely assessed degree of hemolysis to all samples (n=3185) received in the laboratory in a 1-week period. For each test, the correct and incorrect way of handling results was determined. Risk assessment was performed according to ISO 14971 standard with five categories of risk (S1-S5) and error occurrence (O1-O5). RESULTS: In the studied period, the emergency laboratory received 495 hemolyzed samples (15.5%) with a total of 2518 laboratory test requests (15.5%): 102 (20.6%) of the reports from hemolyzed samples had a comment on hemolysis; 31% of the test results were handled incorrectly (20.7% due to the incorrect release of the test result despite hemolysis interference and 10.3% due to unnecessary suppression), accounting for 4.8% of the total test volume. Tests with the highest combination of risk and occurrence rate were troponin T, potassium and total bilirubin. CONCLUSIONS: Manual handling of hemolyzed samples may lead to risk of errors in reporting results for troponin T, potassium and total bilirubin, which may have an effect on clinical decision. In addition, unnecessary suppression of the sample results unaffected by hemolysis could affect patient outcome.

Liquid citrate acidification introduces significant glucose bias and leads to misclassification of patients with diabetes.

BACKGROUND: Glucose measurements are crucial in diabetes diagnosis. We aimed to assess the effectiveness of liquid citrate acidification in preventing glycolysis and investigate glucose stability in serum, sodium fluoride (NaF/KOx) and Glucomedics tubes. METHODS: Samples from 40 participants were collected in serum, lithium-heparin (LiH), sodium fluoride/potassium oxalate (NaF/KOx) and Glucomedics tubes. Glucose was measured within 60 min (baseline), 120 and 180 min from venipuncture. Serum, NaF/KOx and Glucomedics values at baseline were compared to LiH glucose concentration. Additionally, glucose values measured at 120 and 180 min from each tube were compared with the baseline value. Mean absolute bias for each tube and time point was calculated and compared to recommended criteria. The regression equation obtained comparing citrate to NaF/KOx tubes was used to recalculate glucose results retrieved from the laboratory information system. RESULTS: Glucose measured in Glucomedics was higher (9.9%; p<0.001), while glucose in NaF/KOx and serum was lower compared to LiH (2.4%; p<0.001 and 3.2%; p<0.001, respectively). Biases for all tubes were clinically significant. Glucose remained unchanged at room temperature in all tubes for up to 180 min after venipuncture. Observed bias caused by Glucomedics leads to a 10.6% increase in diabetes prevalence (p<0.001). CONCLUSIONS: Inhibition of glycolysis is most effectively achieved using liquid citrate acidification, compared to LiH, NaF/KOx or serum. Due to clinically significant bias relative to reference glucose, the interchangeable use of different tube types for serial glucose measurements is not recommended. The replacement of NaF/KOx with Glucomedics tubes substantially impacts glucose results, giving marked rise in diabetes prevalence.

Glucose is stable during prolonged storage in un-centrifuged Greiner tubes with liquid citrate buffer, but not in serum and NaF/KOx tubes.

BACKGROUND: Delayed sample processing can affect accurate glucose measurement. Our aim was to investigate the stability of glucose in samples collected in serum, sodium fluoride/potassium oxalate (NaF/KOx) and Glucomedics tubes processed according to different controlled pre-centrifugation delays (up to 180 min after venipuncture) in order to simulate prolonged sample transport between venipuncture and centrifugation. METHODS: Samples were collected from healthy volunteers (n=80) into either serum or NaF/KOx and Glucomedics tubes. Glucose concentration was measured in samples centrifuged immediately after venipuncture and compared with tubes processed with a delay of 60, 120 and 180 min prior to centrifugation. Differences between baseline and respective delayed centrifugation glucose value for each tube type were tested using the paired t-test. Mean bias calculated for each tube type and delay protocol was compared to recommended quality specifications for glucose (2.2%). RESULTS: Glucose concentrations measured in all three delayed tube types were lower in comparison to respective baseline glucose concentrations measured in immediately processed tube (p<0.001). The highest decrease in glucose was observed in serum tubes in all specified time points (p<0.001), while glucose was most stable in Glucomedics tubes (p<0.001). The decrease in glucose observed for serum and NaF/KOx tubes was clinically significant at all specified time points while the bias for Glucomedics tubes did not exceed the criteria even with a centrifugation delay of 180 min. CONCLUSIONS: Glucose stability in un-centrifuged Glucomedics tubes is much superior to serum and NaF/KOx tubes. Glucomedics tubes can be left un-centrifuged for up to 3 h without affecting glucose concentration.

Platelet and serum calcium and magnesium concentration in suicidal and non-suicidal schizophrenic patients.

AIM: The main processes modulated by Ca and involved in the cause of schizophrenia are alteration in the dopamine and glutamate neurotransmitter system. Intracellular effects of Mg-ions are opposite to Ca-ions in competition at K-ion channels, in Na/K-ATP-ase activity, cAMP/cGMP concentration and Ca-ion currents in pre- and postsynaptic membranes. We conducted this research due to the incongruent results on Ca and Mg concentration that have been published until now and to determine platelet Mg concentration in suicidal and non-suicidal schizophrenic patients. METHODS: A group of schizophrenic patients consisted of 23 patients with attempted suicide (S-SCH) and 48 patients without suicidal behavior (K-SCH) diagnosed according to ICD-10 diagnosis (F20.0) with or without intentional self-harm (X60-X84). The control group (K) included 99 healthy voluntary blood donors. The Mg and Ca concentration in platelets and serum was determined by atomic absorption spectrophotometry on the AAnalyst 200. RESULTS: Using one-way anova test and manifold application of the Student-Newman-Keuls post-hoc test we established that there were higher concentrations of platelet Mg (µmol/109 platelets) (P=0.009, F=4.89) and lower concentrations of serum Ca (mmol/L) (P<0.001, F=19.18) in the S-SCH group of patients and higher concentrations of platelet Ca/Mg ratio in the K-SCH group of patients (P=0.006, F=5.37). CONCLUSION: A higher Ca/Mg ratio in the platelets of non-suicidal patients confirms indirect higher Ca concentration. Higher Mg concentration in the platelets of suicidal patients, considered a Ca antagonist, may represent a compensatory attempt to restrain Ca activity.

Antipsychotics-induced hyperprolactinemia and screening for macroprolactin.

INTRODUCTION: High prolactin (PRL) concentrations are found in laboratory test results of patients on majority of antipsychotic drugs. Prevalence rates and degrees of severity of hyperprolactinemia (HPRL) based on PRL concentration may depend on the presence of macroprolactin in the serum. The aim of the study was to investigate the difference between PRL concentrations before and after precipitation of macroprolactin and to examine if there were any changes in the categorization of HPRL between samples prior and after precipitation. MATERIALS AND METHODS: Total of 98 female patients (median age 33; range 19-47 years) diagnosed with a psychotic disorder, proscribed antipsychotic drugs, and with HPRL were included. Total PRL concentration and PRL concentration after macroprolactin precipitation with polyethylene glycol (postPEG-PRL) were determined by the chemiluminometric method on the Beckman Coulter Access2 analyser. RESULTS: Total PRL concentrations (median 1471; IQC: 1064-2016 mlU/L) and postPEG-PRL concentrations (median 1453; IQC: 979-1955 mlU/L) were significantly correlated using intraclass correlation coefficient for single measurements (mean estimation 0.96; 95%CI 0.93-0.97) and average measurement (mean estimation 0.98; 95%CI 0.96-0.99), and all investigated female patient had HPRL according to PRL and postPEG-PRL concentration. The median PRL recovery following PEG precipitation was 95; IQC: 90-100%. There was substantial agreement (kappa test = 0.859, 95% CI: 0.764-0.953) between the categories of HPRL severity based on total PRL concentrations and postPEG-PRL concentrations. CONCLUSION: The study demonstrated that HPRL was present in all subjects using the reference interval for total PRL concentration and postPEG-PRL concentration with no significant impact of macroprolactin presence in the serum on the categorization of patients according to severity of HPRL.

The evidence for clinically significant bias in plasma glucose between liquid and lyophilized citrate buffer additive.

OBJECTIVES: Citrate buffer additive has been suggested to be of supreme performance in inhibiting glycolysis. However, there is little evidence in the literature regarding the comparability of glucose concentrations in liquid and lyophilized citrate buffer containing tubes. The aim of this study was to compare glucose concentrations in tubes containing liquid (Glucomedics) and lyophilized citrate buffer (Terumo VENOSAFE™ Glycemia) additive, measured immediately after centrifugation. DESIGN AND METHODS: Blood was collected from forty volunteers into both Glucomedics and Venosafe Glycemia tubes. Blood was centrifuged within 15min from venipuncture and glucose concentration was measured immediately after centrifugation, on the Abbott Architect analyzer. Differences between glucose concentrations in Glucomedics and Terumo tubes were tested using the paired t-test. Mean bias was calculated and compared to recommended quality specification for glucose (i.e. 2.2%). RESULTS: Glucose concentration in Terumo tubes was 3.4% lower than in Glucomedics tubes (P<0.001). The mean bias was clinically significant. CONCLUSIONS: There is a clinically significant difference between glucose concentrations in liquid and lyophilized citrate buffer additive tubes (Glucomedics vs. Terumo tubes) measured immediately after centrifugation. This difference may affect the patient outcome due to the misclassification of diabetes.

Platelet serotonin and magnesium concentrations in suicidal and non-suicidal depressed patients.

The pathophysiology and treatment of depression involves monoamine neurotransmitters and the magnesium (Mg)-modulated monoaminergic pathway. Serum and platelet Mg concentrations and platelet serotonin concentrations were measured in 79 depressed patients who had attempted suicide, and 101 patients without suicidal behaviour, according to the ICD-10 diagnoses F 33.2 and F32.2, with or without intentional self-harm (X60-X84). The control group consisted of 77 voluntary blood donors. The platelet serotonin concentration was determined using the competitive enzyme immunoassay test: Mg concentrations in platelets and serum were determined by atomic absorption spectrophotometry. The ANOVA test showed significantly lower serum Mg in the group of depressive patients who had attempted suicide (N = 257, F = 8.32, p<0.001), compared to depressive patients who had not, and the control group. Serum albumin was lower in the group of depressive patients who had attempted suicide and showed a significant, positive correlation with serum Mg concentrations. Platelet Mg concentrations were found to be higher in depressive patients who had not attempted suicide (N = 257, F = 3.90, p = 0.012) compared to the control group, with no difference compared to depressive patients who had attempted suicide. The Kruskal Wallis test (N = 257, H = 48.54, p<0.0001) showed the lowest concentration of platelet serotonin in the groups of depressed patients with and without suicidal behaviour, compared to the healthy control group. A positive correlation was found between platelet Mg and serotonin concentrations only in the healthy control group. In conclusion, differences were observed in serum and platelet Mg concentrations, which represent progress in the study of Mg status and its relation to serotonin.