Smartphone Application Monitoring of Acceleration Forces During Pneumatic Tube System Transport of Emergency Department Patient Samples.

BACKGROUND: The use of pneumatic tube system (PTS) transport has gained considerable popularity in modern hospitals but is also associated with sample hemolysis. The potential contribution of PTS-associated acceleration forces to high hemolysis rates observed in the emergency department (ED) has not been investigated before and can be easily examined nowadays using smartphone applications. The first aim of our study was to investigate whether our PTS induces hemolysis of patient samples obtained from our ED. We also explored a potential correlation between hemolysis index (HI) on the one hand and acceleration forces during PTS transport or other potential causes of hemolysis related to patient characteristics on the other for two different blood sampling techniques. METHODS: Blood samples from 100 ED patients were collected in one Sarstedt S-Monovette® serum tube (PTStransported to laboratory) and two BD Vacutainer® serum tubes (one PTS-transported and one hand-carried). For all serum samples HI was measured. A smartphone was sent along with the samples in order to register accelerations during transport. Patient's erythrocyte sedimentation rate (ESR), mean corpuscular volume (MCV), hematocrit, total cholesterol, low density lipoprotein (LDL), and high-density lipoprotein (HDL) concentration were determined as well. RESULTS: Hemolysis rate was only 1 - 4% and 5% for PTS and hand-carried transport, respectively. Calculated acceleration vector sums for PTS transport from the ED to laboratory reached up to 131.49 m/second2 (13.40 g). No correlation could be demonstrated between HI on the one hand and acceleration forces acting on the samples during PTS transport or ESR, MCV, hematocrit, and HDL concentration on the other. However, an inverse correlation was noted between HI and cholesterol (total and LDL) concentration in serum tubes transported via PTS, though not in those carried by hand. CONCLUSIONS: We demonstrated that our PTS does not induce or contribute to hemolysis of ED patient samples, even at high acceleration vector sums up to 13 g. Technological advancements such as the development of smartphone applications offer the ability to regularly monitor acceleration forces during PTS transport of patient samples. Low total cholesterol and LDL concentrations may affect the erythrocyte membrane fluidity, making erythrocytes more prone to hemolysis.

Causes, consequences and management of sample hemolysis in the clinical laboratory.

Preanalytical hemolysis of blood samples is a common problem in medical practice, especially in emergency departments. Several potential influences on sample hemolysis have been investigated, including sampling techniques, centrifugation and sample transport. In particular, the use of intravenous catheters and the vacuum sampling technique have often been demonstrated to provoke hemolysis. Other factors playing a role include the use of inappropriate puncture sites, complicated blood sampling, prolonged tourniquet application, underfilling of tubes and excessive shaking of specimens. Training of phlebotomists can play a pivotal role in overcoming these issues. A sample may also undergo hemolysis at the point of centrifugation, more specifically when centrifugation lasts too long or is done repeatedly. Pneumatic tube system (PTS)-transported samples tend to be more strongly affected by hemolysis compared to hand-carried ones, though whether this difference is clinically relevant remains questionable. The velocity at which the sample moves, the distance it covers and the shock forces it sustains all determine to what extent hemolysis occurs during PTS transport. The use of cushion inserts in the carrier to stabilize the samples and the presence of a gel separator in the transported serum tubes may prevent PTS-induced hemolysis. Finally, there is considerable variation between patients in the extent to which samples are prone to hemolysis. Sample hemolysis leads to unreliable laboratory results, delayed diagnosis and patients suffering avoidable discomfort. Specifically, hemolysis may interfere with laboratory results due to release of intracellular components, dilution effects, proteolysis and interference with analytical techniques. There is ongoing debate about how laboratories should deal with results altered by hemolysis. Laboratory specialists should clearly communicate with the ordering clinicians in order to make an informed decision about how to interpret hemolysis-affected analytical results. This review looks into current evidence concerning the causes and consequences of in vitro hemolysis, and aims to explain how to deal with it.

Glucose-6-phosphate dehydrogenase deficiency: not exclusively in males.

Glucose-6-phosphate (G6PD) deficiency is the most common human enzyme defect, often presenting with neonatal jaundice and/or acute hemolytic anemia, triggered by oxidizing agents. G6PD deficiency is an X-linked, hereditary disease, mainly affecting men, but should also be considered in females with an oxidative hemolysis.

An update on the role of carboxypeptidase U (TAFIa) in fibrinolysis.

Since its discovery more than 20 years ago, a lot has been revealed about the biochemistry and physiological behaviour of carboxypeptidase U (CPU). Recent advances in CPU research include the unravelling of the crystal structure of proCPU and revealing the molecular mechanisms for the marked instability of the active enzyme, CPU. The recent development of two highly sensitive assays has cleared the path toward the direct measurement of CPU in circulation or the determination of CPU generation, rather than the measurement of total proCPU concentration in plasma. Finally, since CPU is known to have a prominent bridging function between coagulation and fibrinolysis, the development of CPU inhibitors as profibrinolytic agents is an attractive new concept and has gained a lot of interest from several research groups and from the pharmaceutical industry. These recent advances in CPU research are reviewed in this literature update.

Measurement of carboxypeptidase U (active thrombin-activatable fibrinolysis inhibitor) in plasma: Challenges overcome by a novel selective assay.

This article introduces a novel assay for the measurement of carboxypeptidase U (CPU) in plasma using the selective CPU substrate Bz-o-cyano-Phe-Arg (N-benzoyl-ortho-cyano-phenylalanyl-arginine), thereby limiting the interference of plasma carboxypeptidase N (CPN) as well as the intrinsic activity of procarboxypeptidase U (proCPU). A limit of detection of 0.05 U/L (10 pM) was reached. In addition, the current assay has the advantage of being easy to perform and shows excellent linearity and variability, rendering it a useful tool in the screening of samples for the presence of CPU in several patient populations and encouraging in-depth exploration of the pathophysiological role of the proCPU/CPU system.

Thrombin activatable fibrinolysis inhibitor (TAFI): a molecular link between coagulation and fibrinolysis.

Although the maintenance of precise balance between coagulation and fibrinolysis is of utmost importance for normal haemostasis, until recently these two systems were considered as completely separate mechanisms involved in the process of formation and dissolution of blood clot. Thrombin activatable fibrinolysis inhibitor (TAFI) is a recently described attenuator of the fibrinolytic rate and is considered to be the molecular link between coagulation and fibrinolysis. TAFI circulates in plasma as an inactive precursor and its conversion in active enzyme (TAFIa) occurs by the action of thrombin or plasmin, but most efficiently by thrombin in the presence of its cofactor thrombomodulin. Once generated, TAFI down-regulates fibrinolysis by removing C-terminal lysine residues from partially degraded fibrin; thereby preventing the upregulation of plasminogen binding and activation. Because TAFI is activated by thrombin on one side, and acts as the attenuator of fibrinolysis on another side, it enables fine synchronization between these two systems. The antifibrinolytic function of TAFI mostly depends on TAFI concentration, the rate of its activation and the half-life of TAFIa in plasma. Changes in thrombin generation can have a profound effect on the rate of TAFI activation, and consequently on the rate of fibrinolysis. Therefore, it has been hypothesized that increased thrombin generation seen in thrombophilia patients may enhance TAFI activation, leading to a hypofibrinolytic state, which may further contribute to the thrombotic tendency. However, the results of several studies, in which relation between TAFI level and the occurrence of thromboembolic complications in carriers of hereditary thrombophilia have been investigated, were not consistent.

Development of a sensitive and selective assay for the determination of procarboxypeptidase U (thrombin-activatable fibrinolysis inhibitor) in plasma.

To date, several assays for procarboxypeptidase U (proCPU) determination exist, all having their own inherent disadvantages and advantages. A drawback of activity-based assays is the interference of the constitutively active carboxypeptidase N (CPN) in plasma. Recent screening of Bz-Xaa-Arg peptides with modified aromatic amino acids at the P1 position revealed a selective CPU substrate, N-benzoyl-ortho-cyano-phenylalanyl-arginine (Bz-o-cyano-Phe-Arg), which will allow straightforward determination of proCPU in plasma. Our assay shows an excellent linearity in the concentration range of 20-2600 U/L, with within- and between-run precision values of 2.7% and 4.6%, respectively. A good correlation with our high-performance liquid chromatography (HPLC)-assisted proCPU activity assay using hippuryl-l-arginine (HipArg) as substrate was found. Besides the major improvement regarding the selectivity, the assay is much easier to perform and far less time-consuming compared with the proCPU activity assay using HipArg as substrate.

Procarboxypeptidase U (TAFI) contributes to the risk of thrombosis in patients with hereditary thrombophilia.

INTRODUCTION: It is considered that high plasma levels of procarboxypeptidase U (proCPU or TAFI) can promote the development of thrombosis, but data comparing proCPU levels in thrombophilia carriers and healthy subjects are rather scarce. Moreover, the results of previous studies on the risk of thrombosis related to high proCPU concentration in this population were not consistent. Although the 325 polymorphism of proCPU has a significant effect on the CPU half-life, it's influence on the risk of thrombosis or spontaneous pregnancy loss in carriers of hereditary thrombophilia is not clear. MATERIALS AND METHODS: The study population consisted of 144 thrombophilic patients (94 heterozygous and 10 homozygous carriers of FV Leiden, 26 heterozygous carriers of the prothrombin G20210A variation and 14 double carriers of FV Leiden and FII variation) and 69 healthy controls. RESULTS: The results show that patients with inherited thrombophilia have a tendency toward lower mean proCPU plasma levels compared to healthy controls, however, this difference was only significant in carriers of FII G20210A (p=0.014). A higher frequency of the most stable Ile325Ile proCPU was seen among carriers of FII G20210A mutation compared to the control group (19% vs 7%; p=0.186). In the second part of the study proCPU as a risk factor for thrombosis was evaluated. In heterozygous carriers of FV Leiden or FII G20210A high levels of proCPU conferred to an almost 4-fold increased risk for spontaneous onset thrombosis. The more stable Ile325Ile proCPU seems to impose a higher risk for clinical manifestation of the thrombophilic condition. Finally, a significant positive correlation between F1+2 and proCPU concentration was seen. CONCLUSION: The increased risk of thrombosis in thrombophilia patients is not only ascribable to an increased thrombin generation, but also high levels of proCPU and the presence of the 325Ile genotype tip the balance towards thrombotic tendency even further.

Carboxypeptidase U (TAFIa) decreases the efficacy of thrombolytic therapy in ischemic stroke patients.

INTRODUCTION: Thrombolytic therapy improves clinical outcome in patients with acute ischemic stroke but is compromised by symptomatic intracranial hemorrhage and an unpredictable therapeutic response. In vitro and in vivo data suggest that activation of procarboxypeptidase U (proCPU) inhibits fibrinolysis. AIMS: To investigate whether the extent of proCPU activation is related to efficacy and safety of thrombolytic therapy in ischemic stroke patients. METHODS: In twelve patients with ischemic stroke who were treated with intravenous (n=7) or intra-arterial (n=5) thrombolysis, venous blood samples were taken at different time points before, during and after thrombolytic therapy. ProCPU and carboxypeptidase U (CPU, TAFIa) plasma concentrations were determined by HPLC. The maximal CPU activity (CPU(max)) and the percentage of proCPU consumption during thrombolytic therapy were calculated. The efficacy and safety of the thrombolytic therapy were assessed by evolution of the clinical deficit, recanalisation, final infarct volume, thrombolysis-induced intracranial hemorrhage and mortality. RESULTS: No correlations between CPU(max) or proCPU consumption and patient or stroke characteristics were found. However, CPU(max) is associated with evolution of the clinical deficit and achieved recanalisation. ProCPU consumption is related to the risk of intracranial hemorrhage, mortality and final infarct volume. CONCLUSIONS: Irrespective of patient and stroke characteristics, CPU(max) and proCPU consumption during thrombolytic treatment for ischemic stroke are parameters for therapeutic efficacy and safety. Further evaluation of the clinical applicability of these parameters and further investigation of the potential role for CPU inhibitors as adjunctive therapeutics during thrombolytic treatment may be of value.