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.

Paraoxonase 1 activity in patients with chronic obstructive pulmonary disease.

INTRODUCTION: Paraoxonase 1 (PON1) is an antioxidative enzyme manly associated with high density lipoproteins (HDL) in the peripheral blood. The aim of this study was to determine the PON1 paraoxonase and arylesterase activities in patients with chronic obstructive pulmonary disease (COPD). We also aimed to determine the concentration of reduced thiol groups as a marker of protein oxidation. MATERIALS AND METHODS: The study included 105 patients with stable COPD and 44 healthy controls. PON1 activities and thiols concentration were assayed in sera by spectrophotometry. RESULTS: PON1 basal (POX) and salt-stimulated paraoxonase activity (POX1) as well as arylesterase activity (ARE) were significantly reduced in COPD patients. In addition, concentration of reduced thiol groups was significantly decreased in COPD group. PON1 activities were similar in patients with different disease severity (GOLD stages). However, a significant reduction in POX, POX1 and ARE was observed already in GOLD II stage when compared to controls. POX and POX1 showed modest while ARE yielded very good power for discrimination between healthy subjects and COPD patients. Univariate and multivariate logistic regression analysis indicated that ARE is a good COPD predictor. CONCLUSION: Reduction of PON1 activity observed in COPD patients could be partly caused by oxidative environment. Lower concentrations of reduced thiol groups in COPD patients suggest that a decrease in PON1 activity could reflect oxidative changes of enzyme free cysteine residues. Furthermore, decreased PON1 arylesterase activity might indicate a down-regulation of PON1 concentration. Our results suggest that ARE could be considered as potential biomarker for COPD diagnosis.

Blood gas testing and related measurements: National recommendations on behalf of the Croatian Society of Medical Biochemistry and Laboratory Medicine.

Blood gas analysis (BGA) is exposed to risks of errors caused by improper sampling, transport and storage conditions. The Clinical and Laboratory Standards Institute (CLSI) generated documents with recommendations for avoidance of potential errors caused by sample mishandling. Two main documents related to BGA issued by the CLSI are GP43-A4 (former H11-A4) Procedures for the collection of arterial blood specimens; approved standard - fourth edition, and C46-A2 Blood gas and pH analysis and related measurements; approved guideline - second edition. Practices related to processing of blood gas samples are not standardized in the Republic of Croatia. Each institution has its own protocol for ordering, collection and analysis of blood gases. Although many laboratories use state of the art analyzers, still many preanalytical procedures remain unchanged. The objective of the Croatian Society of Medical Biochemistry and Laboratory Medicine (CSMBLM) is to standardize the procedures for BGA based on CLSI recommendations. The Working Group for Blood Gas Testing as part of the Committee for the Scientific Professional Development of the CSMBLM prepared a set of recommended protocols for sampling, transport, storage and processing of blood gas samples based on relevant CLSI documents, relevant literature search and on the results of Croatian survey study on practices and policies in acid-base testing. Recommendations are intended for laboratory professionals and all healthcare workers involved in blood gas processing.

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.

Laboratory testing of extravascular body fluids in Croatia: a survey of the Working group for extravascular body fluids of the Croatian Society of Medical Biochemistry and Laboratory Medicine.

INTRODUCTION: We hypothesized that extravascular body fluid (EBF) analysis in Croatia is not harmonized and aimed to investigate preanalytical, analytical and postanalytical procedures used in EBF analysis in order to identify key aspects that should be addressed in future harmonization attempts. MATERIALS AND METHODS: An anonymous online survey created to explore laboratory testing of EBF was sent to secondary, tertiary and private health care Medical Biochemistry Laboratories (MBLs) in Croatia. Statements were designed to address preanalytical, analytical and postanalytical procedures of cerebrospinal, pleural, peritoneal (ascites), pericardial, seminal, synovial, amniotic fluid and sweat. Participants were asked to declare the strength of agreement with proposed statements using a Likert scale. Mean scores for corresponding separate statements divided according to health care setting were calculated and compared. RESULTS: The survey response rate was 0.64 (58 / 90). None of the participating private MBLs declared to analyse EBF. We report a mean score of 3.45 obtained for all statements evaluated. Deviations from desirable procedures were demonstrated in all EBF testing phases. Minor differences in procedures used for EBF analysis comparing secondary and tertiary health care MBLs were found. The lowest scores were obtained for statements regarding quality control procedures in EBF analysis, participation in proficiency testing programmes and provision of interpretative comments on EBF's test reports. CONCLUSIONS: Although good laboratory EBF practice is present in Croatia, procedures for EBF analysis should be further harmonized to improve the quality of EBF testing and patient safety.

Croatian survey on critical results reporting.

INTRODUCTION: Poor harmonization of critical results management is present in various laboratories and countries, including Croatia. We aimed to investigate procedures used in critical results reporting in Croatian medical biochemistry laboratories (MBLs). MATERIALS AND METHODS: An anonymous questionnaire, consisting of 24 questions/statements, related to critical results reporting procedures, was send to managers of MBLs in Croatia. Participants were asked to declare the frequency of performing procedures and degree of agreement with statements about critical values reporting using a Likert scale. Total score and mean scores for corresponding separate statements divided according to health care setting were calculated and compared. RESULTS: Responses from 111 Croatian laboratories (48%) were analyzed. General practice laboratories (GPLs) more often re-analyzed the sample before reporting the critical result in comparison with the hospital laboratories (HLs) (score: 4.86 (4.75-4.96) vs. 4.49 (4.25-4.72); P=0.001) and more often reported the critical value exclusively to the responsible physician compared to HLs (4.46 (4.29-4.64) vs. 3.76 (3.48-4.03), P<0.001). High total score (4.69 (4.56-4.82)) was observed for selection of the critical results list issued by the Croatian Chamber of Medical Biochemistry (CCMB) indicating a high harmonization level for this aspect of critical result management. Low total scores were observed for the statements regarding data recording and documentation of critical result notification. CONCLUSIONS: Differences in practices about critical results reporting between HLs and GPLs were found. The homogeneity of least favorable responses detected for data recording and documentation of critical results notification reflects the lack of specific national recommendations.

Pleural, peritoneal and pericardial effusions - a biochemical approach.

The pathological accumulation of serous fluids in the pleural, peritoneal and pericardial space occurs in a variety of conditions. Since patient management depends on right and timely diagnosis, biochemical analysis of extravascular body fluids is considered a valuable tool in the patient management process. The biochemical evaluation of serous fluids includes the determination of gross appearance, differentiation of transudative from exudative effusions and additional specific biochemical testing to assess the effusion etiology. This article summarized data from the most relevant literature concerning practice with special emphasis on usefulness of biochemical tests used for the investigation of pleural, peritoneal and pericardial effusions. Additionally, preanalytical issues concerning serous fluid analysis were addressed and recommendations concerning acceptable analytical practice in serous fluid analysis were presented.

Platelet satellitism in a trauma patient.

Platelet satellitism (PS) is a rare phenomenon observed in blood smears obtained from blood anticoagulated with EDTA. It is characterised by platelet rosetting around polymorphonuclear neutrophils and in rare cases around other blood cells. PS is a rare cause of pseudothrombocytopenia. References about the phenomenon of PS in medical literature are few. In this report we describe a case of PS fortunately noticed in one trauma patient. Furthermore, we discuss the possible pathophysiological mechanisms of PS proposed in the literature. To our knowledge this is the first case of PS reported in Croatia.