A metabolic investigation of arterialized venous flaps in rabbits using mass spectrometry-based metabolomics.

An arterialized venous flap (AVF) is an ideal choice of flap to repair wounds. However, the survival of these flaps remains the source of some concern. This study used metabolomic analysis to investigate the mechanisms underlying survival in AVF flaps in order to guide the clinical application of these flaps. Thirty-six male Japanese rabbits were randomly divided into a sham group and an AVF group. They were used for histology and hemodynamic investigations. Three days after surgery, tissue samples were analyzed by mass spectroscopy-based metabolomics. The results of the study revealed a reduction in blood flow, infiltration of inflammatory cells, and necrosis of flaps in the AVF group. In addition, notable changes were evident in the levels of several metabolites in the AVF group, including lactic acid, acetoacetic acid, inositol phosphate, arachidonic acid, and other metabolites. Our results indicate that the AVF group experienced changes in several biological pathways, including energy metabolism, cell membrane stability, and inflammatory response. There is a significant metabolic difference between AVFs and physiological flaps. The dysregulation in certain metabolites may be related to the specific hemodynamics and insufficient energy metabolism of the AVFs.

Three-dimensional visualization of cleared human pancreas cancer reveals that sustained epithelial-to-mesenchymal transition is not required for venous invasion.

Venous invasion is three times more common in pancreatic cancer than it is in other major cancers of the gastrointestinal tract, and venous invasion may explain why pancreatic cancer is so deadly. To characterize the patterns of venous invasion in pancreatic cancer, 52 thick slabs (up to 5 mm) of tissue were harvested from 52 surgically resected human ductal adenocarcinomas, cleared with a modified iDISCO method, and labeled with fluorescent-conjugated antibodies to cytokeratin 19, desmin, CD31, p53 and/or e-cadherin. Labeled three-dimensional (3D) pancreas cancer tissues were visualized with confocal laser scanning or light sheet microscopy. Multiple foci of venous and even arterial invasion were visualized. Venous invasion was detected more often in 3D (88%, 30/34 cases) than in conventional 2D slide evaluation (75%, 25/34 cases, P < 0.001). 3D visualization revealed pancreatic cancer cells crossing the walls of veins at multiple points, often at points where preexisting capillary structures bridge the blood vessels. The neoplastic cells often retained a ductal morphology (cohesive cells forming tubes) as they progressed from a stromal to intravenous location. Although immunolabeling with antibodies to e-cadherin revealed focal loss of expression at the leading edges of the cancers, the neoplastic cells within veins expressed e-cadherin and formed well-oriented glands. We conclude that venous invasion is almost universal in pancreatic cancer, suggesting that even surgically resectable PDAC has access to the venous spaces and thus the ability to disseminate widely. Furthermore, we observe that sustained epithelial-mesenchymal transition is not required for venous invasion in pancreatic cancer.

Assessing Acid-Base Status in Circulatory Failure: Relationship Between Arterial and Peripheral Venous Blood Gas Measurements in Hypovolemic Shock.

BACKGROUND AND OBJECTIVES: In severe circulatory failure agreement between arterial and mixed venous or central venous values is poor; venous values are more reflective of tissue acid-base imbalance. No prior study has examined the relationship between peripheral venous blood gas (VBG) values and arterial blood gas (ABG) values in hemodynamic compromise. The objective of this study was to examine the correlation between hemodynamic parameters, specifically systolic blood pressure (SBP) and the arterial-peripheral venous (A-PV) difference for all commonly used acid-base parameters (pH, Pco 2, and bicarbonate). DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS: Data were obtained prospectively from adult patients with trauma. When an ABG was obtained for clinical purposes, a VBG was drawn as soon as possible. Patients were excluded if the ABG and VBG were drawn >10 minutes apart. RESULTS: The correlations between A-PV pH, A-PV Pco 2, and A-PV bicarbonate and SBP were not statistically significant (P = .55, .17, and .09, respectively). Although patients with hypotension had a lower mean arterial and peripheral venous pH and bicarbonate compared to hemodynamically stable patients, mean A-PV differences for pH and Pco 2 were not statistically different (P = .24 and .16, respectively) between hypotensive and normotensive groups. CONCLUSIONS: In hypovolemic shock, the peripheral VBG does not demonstrate a higher CO2 concentration and lower pH compared to arterial blood. Therefore, the peripheral VBG is not a surrogate for the tissue acid-base status in hypovolemic shock, likely due to peripheral vasoconstriction and central shunting of blood to essential organs. This contrasts with the selective venous respiratory acidosis previously demonstrated in central venous and mixed venous measurements in circulatory failure, which is more reflective of acid-base imbalance at the tissue level than arterial blood. Further work needs to be done to better define the relationship between ABG and both central and peripheral VBG values in various types of shock.

TEMPORAL STABILITY OF IN VITRO VENOUS BLOOD GAS, pH, AND LACTATE VALUES OF COWNOSE RAYS (RHINOPTERA BONASUS) AND RED-EARED SLIDER TURTLES (PSEUDEMYS SCRIPTA ELEGANS).

This study assessed the in vitro temporal changes that occur in blood pH and lactate concentrations for an elasmobranch species and a chelonian species, as well as blood gases (partial pressures of carbon dioxide [pCO2] and oxygen [pO2]) for a chelonian species, with a portable clinical point-of-care analyzer. Blood samples were collected from 10 cownose rays (Rhinoptera bonasus) and 10 red-eared sliders (Pseudemys scripta elegans), stored on ice, and serially analyzed at six time points up to 90 min postcollection. Results indicate that analysis should be conducted as soon as possible after blood collection for these species, with immediate analysis being preferred. However, if analysis must be delayed, syringes may be capped, placed on ice, and analyzed at a later time. Analysis within 90 min provided clinically acceptable results for pH and lactate in both species and for pCO2 in red-eared sliders, whereas substantial artifactual increases of pO2 were seen in red-eared sliders.

A comparison between point-of-care testing and venous glucose determination for the diagnosis of diabetes mellitus 6-12 weeks after gestational diabetes.

AIM: To evaluate point-of-care-testing (POCT) for the diagnosis of Type 2 diabetes mellitus 6-12 weeks post-partum in women with gestational diabetes (GDM). METHODS: Post-partum glucose assessment (75-mg oral glucose tolerance test, OGTT) was performed prospectively in 122 women with GDM (1 November 2015 to 1 November 2017) at Tygerberg Hospital, Cape Town, South Africa. Individuals with known pre-existing diabetes were excluded. The accuracy and clinical utility of POCT (capillary finger-prick) were compared with laboratory plasma glucose (hexokinase and glucokinase methods). The OGTT consisted of two time points (fasting and 2 h) during which concurrent glucose samples (POCT and laboratory) were obtained. Bland-Altman plots and paired analysis were used to assess the analytical accuracy of POCT, whereas its diagnostic performance was determined using positive and negative predictive values to calculate specificity and sensitivity. RESULTS: Spearman's ranked correlation analysis indicated a strong association between POCT and laboratory glucose values at both OGTT time points (fasting, r = 0.95, P < 0.0001; 2 h, r = 0.88, P < 0.0001). Thirty-six women were diagnosed with Type 2 diabetes based on gold standard laboratory glucose levels (fasting > 7 mmol/l; 2 h > 11.1 mmol/l). POCT correctly identified Type 2 diabetes in 78% of women (28 of 36) with a positive predictive value of 89.3% and a negative predictive value of 96.7% at the fasting time point. The sensitivity and specificity of POCT to diagnose Type 2 diabetes were 89% (fasting), 85.7% (2 h) and 96.7% (fasting), 98.5% (2 h) respectively. POCT proved less sensitive to diagnose pre-diabetes (69%) but displayed satisfactory specificity (92%) at both time points assessed. CONCLUSION: POCT accurately identifies women with Type 2 diabetes 6-12 weeks after GDM.

Histopathological and proteomic analyses identify integrin-ß1 as a potential mediator of phlebosclerosis in uremic patients.

BACKGROUND: Patients with uremia have an excessive mortality from cardiovascular disease (CVD). Arterial remodeling is mainly responsible for uremia-induced CVD and has been well studied, yet venous remodeling is poorly understood. Here we investigate the histopathology and proteomic profiles of venous remodeling in uremic patients. METHODS: Forearm cephalic veins were isolated from nine uremic patients during surgeries for arteriovenous fistula, and from nine healthy controls when applying surgical debridement. Hematoxylin-eosin, Masson's trichrome, von Kossa, and immunohistochemistry (IHC) against proliferating cell nuclear antigen were stained for histopathology. Isobaric tags for relative and absolute quantitation (iTRAQ) proteomic analysis was executed to explore the proteome of the veins. The core regulatory protein was validated by western blot, IHC, and immunofluorescence. RESULTS: Phlebosclerosis, characterized by intimal rarefaction and medial thickening with disordered proliferation of vascular smooth muscle cells (VSMCs), was the prominent pathological manifestation of peripheral veins in uremic patients, while inflammatory cell infiltration, atherosclerosis or calcification were not obviously detected. iTRAQ analysis showed that 350 proteins were significantly changed in phlebosclerosis of uremic patients compared with healthy controls, of which integrin-ß1 (ITGß1) exhibited the strongest regulatory ability by intermolecular interaction network analysis. The enhanced ITGß1 expression was mainly co-expressed with the disordered proliferation of VSMCs while a little with vascular endothelial cells in the forearm cephalic veins of uremic patients. CONCLUSIONS: Phlebosclerosis is the prominent pathological manifestation in peripheral veins of uremic patients. This pathological alteration mainly attributes to the disordered proliferation of VSMCs, which is potentially mediated by ITGß1.

VENOUS AND ARTERIAL ACID-BASE ANALYSIS OF MAGELLANIC PENGUINS (SPHENISCUS MAGELLANICUS), AWAKE AND ANESTHETIZED BY ISOFLURANE.

This study aimed to compare the venous acid-base status of healthy awake versus anesthetized Magellanic penguins (Spheniscus magellanicus). Ten nonanesthetized penguins were manually restrained, and a venous blood sample was collected. Six of these penguins were anesthetized by 2% isoflurane and, after an anesthetic stabilization period, both venous and arterial blood samples were simultaneously withdrawn. Using an i-STAT analyzer, partial pressure of carbon dioxide (PCO2), partial pressure of oxygen (PO2), pH, standard bicarbonate concentration (HCO3-), total carbon dioxide (ctCO2), oxygen saturation (SO2), base excess (BE), Na+, and K+ levels were measured in venous blood samples of awake (Gawake) penguins and in venous (Gven) and arterial blood (Gart) samples of anesthetized penguins. There were no significant differences between groups in pH, BE, or Na+. Venous carbon dioxide pressure, HCO3-, and venous ctCO2 were higher in Gven than Gawake penguins, whereas PCO2 was higher in Gven than Gart penguins. PO2 and SO2 were higher in the Gart group than in the other groups. Both venous and arterial blood samples may be used to evaluate the acid-base profile of Magellanic penguins.

Prevention of vein graft intimal hyperplasia with photochemical tissue passivation.

OBJECTIVE: Saphenous vein is the conduit of choice for bypass grafting. Saphenous vein grafts have poor long-term patency rates because of intimal hyperplasia (IH) and subsequent accelerated atherosclerosis. One of the primary triggers of IH is endothelial injury resulting from excessive dilation of the vein after exposure to arterial pressures. Photochemical tissue passivation (PTP) is a technology that cross-links adventitial collagen by a light-activated process, which limits dilation by improving vessel compliance. The objective of this study was to investigate whether PTP limits the development of IH in a rodent venous interposition graft model. METHODS: PTP is accomplished by coating venous adventitia with a photosensitizing dye and exposing it to light. To assess the degree of collagen cross-linking after PTP treatment, a biodegradation assay was performed. Venous interposition grafts were placed in the femoral artery of Sprague-Dawley rats. Rats were euthanized after 4 weeks, and intimal thickness was measured histologically. Vein dilation at the time of the initial procedure was also measured. RESULTS: Time to digestion was 63 ± 7 minutes for controls, 101 ± 2.4 minutes for rose bengal (RB), and 300 ± 0 minutes for PTP (P < .001 PTP vs control). A total of 37 animals underwent the procedure: 12 PTP, 12 RB only, and 13 untreated controls. Dilation of the graft after clamp release was 99% for control, 65% for RB only, and 19% for PTP-treated (P < .001 PTP vs control). Intimal thickness was 77 ± 59 µm in controls, 60 ± 27 µm in RB only, and 33 ± 28 µm in PTP-treated grafts. There was a statistically significant 57% reduction in intimal thickness after treatment with PTP compared with untreated controls (P = .03). CONCLUSIONS: PTP treatment of venous interposition grafts in a rat model resulted in significant collagen cross-linking, decreased vessel compliance, and significant reduction in IH.

Nodular Proliferation in Parkes Weber Syndrome.

Parkes Weber syndrome (PWS) is characterized by the association of high flow vascular malformation and overgrowth of a part of the body, usually a limb. In a previous review of 10 patients with PWS from our hospital we described a case of congenital short femur and four cases of severe lymphedema. We present a case of PWS associated with a nodular proliferative form not previously described. A 38 year old male with diagnosis of PWS with involvement of the right lower limb (RLL) was derived to our clinic. He complained about the appearance of painful nodular tumors in his RLL and some episodes of bleeding through the tumors. The physical examination revealed increased size of the RLL compared to left lower limb. Two nodular tumors were evident in his RLL. One located proximal in the leg and another one in ankle. The computed tomographic angiography revealed multiple arterio-venous shunts in the RLL. The tumors were not arterio-venous shunts, neither aneurysms. We decided to make surgical resection of the tumors. In the pathology analysis the tumors were positive for CD31, CD34 and negative for D240 markers. Eight months after surgery the patient had no recurrence of the tumors, and he is asymptomatic.The presence of nodular tumors in PWS has not been previously described. This makes us to think that these could be hamartomatous lesions similar to those of the CLOVES syndrome or a PIK3CA mutation.

Capillary and Venous Lactate Agreement: a pilot prospective observational study.

BACKGROUND: Blood lactate is a marker of patient illness severity. Capillary lactate (CAP-LACT) measurement can potentially improve patient screening; however, it has poor evidence of clinical utility. AIM: We aimed to investigate agreement between CAP-LACT and peripheral venous lactate (PV-LACT). METHODS: We performed a prospective observational pilot study of 99 patients requiring lactate measurement. Paired CAP-LACT and PV-LACT was recorded. Agreement was determined by Bland-Altman analysis. RESULTS: Bias was 0.2 mmol/L, with 95% limits of agreement from -1.9 to 2.3. CONCLUSIONS: CAP-LACT has poor agreement with PV-LACT. Further research is needed to improve its potential clinical utility.

Deficiency of endothelium-specific transcription factor Sox17 induces intracranial aneurysm.

BACKGROUND: Intracranial aneurysm (IA) is a common vascular disorder that frequently leads to fatal vascular rupture. Although various acquired risk factors associated with IA have been identified, the hereditary basis of IA remains poorly understood. As a result, genetically modified animals accurately modeling IA and related pathogenesis have been lacking, and subsequent drug development has been delayed. METHODS AND RESULTS: The transcription factor Sox17 is robustly expressed in endothelial cells of normal intracerebral arteries. The combination of Sox17 deficiency and angiotensin II infusion in mice induces vascular abnormalities closely resembling the cardinal features of IA such as luminal dilation, wall thinning, tortuosity, and subarachnoid hemorrhages. This combination impairs junctional assembly, cell-matrix adhesion, regeneration capacity, and paracrine secretion in endothelial cells of intracerebral arteries, highlighting key endothelial dysfunctions that lead to IA pathogenesis. Moreover, human IA samples showed reduced Sox17 expression and impaired endothelial integrity, further strengthening the applicability of this animal model to clinical settings. CONCLUSIONS: Our findings demonstrate that Sox17 deficiency in mouse can induce IA under hypertensive conditions, suggesting Sox17 deficiency as a potential genetic factor for IA formation. The Sox17-deficient mouse model provides a novel platform to develop therapeutics for incurable IA.

Leptin, pre-existing vascular disease, and increased arteriovenous fistula maturation failure in dialysis patients.

BACKGROUND: The adipocytokine leptin is an independent cardiovascular risk factor and exerts proatherogenic effect. Pre-existing vascular disease is an important cause of arteriovenous fistula (AVF) maturation failure. We explored the association between serum leptin, pre-existing vascular disease, and AVF maturation failure in incident hemodialysis patients. METHODS: Vein samples from 62 patients were collected at the time of AVF creation. Pre-existing vascular disease was evaluated with histologic changes and immunohistochemical characteristics of cellular phenotypes in intima. AVF maturation failure was defined as an AVF that could not be used successfully by the third month after its creation. RESULTS: The prevalence of body mass index ≥30 kg/m2 was 17%, and AVF maturation failure occurred in 28 (45%) patients. Patients within the highest leptin tertile showed significantly higher maturation failure rate, independent of age, gender, diabetes, and body mass index. On histologic examination, significant differences in intimal hyperplasia (13.3 ± 4.5 vs 18.2 ± 5.2 vs 30.3 ± 14.3 µm) and medial thickening (76.8 ± 23.7 vs 103.9 ± 33.6 vs 109.3 ± 36.5 µm) were observed across leptin tertiles. Similarly, medial fibrosis was most severe in the highest tertile. According to the immunohistochemical staining, most intimal cells were α-smooth muscle actin-positive, vimentin-positive, desmin-negative myofibroblasts. However, in the lowest tertile, desmin-positive contractile smooth muscle cells were also frequently observed, suggesting relatively slow phenotypic changes in this group. Furthermore, as leptin tertiles increased, the expression of leptin receptor in the luminal border of intima was significantly decreased. CONCLUSIONS: Obesity-related higher fistula maturation failure rate may be partly mediated by higher leptin level-associated pre-existing vascular diseases in end-stage renal disease patients. Decreased expression of leptin receptor may be related to this association.

Estrogen Receptors and Chronic Venous Disease.

OBJECTIVE/BACKGROUND: Chronic venous disease (CVD) is a common and relevant problem affecting Western people. The role of estrogens and their receptors in the venous wall seems to support the major prevalence of CVD in women. The effects of the estrogens are mediated by three estrogen receptors (ERs): ERα, ERß, and G protein-coupled ER (GPER). The expression of ERs in the vessel walls of varicose veins is evaluated. METHODS: In this prospective study, patients of both sexes, with CVD and varicose veins undergoing open venous surgery procedures, were enrolled in order to obtain vein samples. To obtain control samples of healthy veins, patients of both sexes without CVD undergoing coronary artery bypass grafting with autologous saphenous vein were recruited (control group). Samples were processed in order to evaluate gene expression. RESULTS: Forty patients with CVD (10 men [25%], 30 women [75%], mean age 54.3 years [median 52 years, range 33-74 years]) were enrolled. Five patients without CVD (three men, two women [aged 61-73 years]) were enrolled as the control group. A significant increase of tissue expression of ERα, ERß and GPER in patients with CVD was recorded (p < .01), which was also related to the severity of venous disease. CONCLUSION: ERs seem to play a role in CVD; in this study, the expression of ERs correlated with the severity of the disease, and their expression was correlated with the clinical stage.

Optimization of metabolite extraction of human vein tissue for ultra performance liquid chromatography-mass spectrometry and nuclear magnetic resonance-based untargeted metabolic profiling.

Human vein tissue is an important matrix to examine when investigating vascular diseases with respect to understanding underlying disease mechanisms. Here, we report the development of an extraction protocol for multi-platform metabolic profiling of human vein tissue. For the first stage of the optimization, two different ratios of methanol/water and 5 organic solvents--namely dichloromethane, chloroform, isopropanol, hexane and methyl tert-butyl ether (MTBE) solutions with methanol--were tested for polar and organic compound extraction, respectively. The extraction output was assessed using (1)H Nuclear Magnetic Resonance (NMR) spectroscopy and a panel of Ultra Performance Liquid Chromatography-Mass Spectrometry (UPLC-MS) methodologies. On the basis of the reproducibility of extraction replicates and metabolic coverage, the optimal aqueous (methanol/water) and organic (MTBE/methanol) solvents identified from the first stage were used in a sequential approach for metabolite extraction, altering the order of solvent-mixture addition. The combination of organic metabolite extraction with MTBE/methanol (3 : 1) followed by extraction of polar compounds with methanol/water (1 : 1) was shown to be the best method for extracting metabolites from human vein tissue in terms of reproducibility and number of signals detected and could be used as a single extraction procedure to serve both NMR and UPLC-MS analyses. Molecular classes such as triacylglycerols, phosphatidylcholines, phosphatidylethanolamines, sphingolipids, purines, and pyrimidines were reproducibly extracted. This study enabled an optimal extraction protocol for robust and more comprehensive metabolome coverage for human vein tissue. Many of the physiological and pathological processes affecting the composition of human vein tissue are common to other tissues and hence the extraction method developed in this study can be generically applied.

Detection of targets and their mechanisms for early diagnosis of traumatic deep vein thrombosis.

The purpose of this investigation was to identify targets for the early diagnosis and predictors of deep venous thrombosis (DVT) and the role of these targets in the formation of venous thrombosis. A model of DVT was constructed in rats. Thromboses and venous walls were sampled for reverse transcription polymerase chain reaction study, and blood was sampled for enzyme-linked immunosorbent assay studies. Vein endothelial cells were cultured to observe the effects of interleukin (IL)-17 on the expression of tissue plasminogen activator (t-PA)/plasminogen activator inhibitor type 1 (PAI-1). IL-17 monoclonal antibody was used to study its effect on preventing the formation of DVT. One-hundred and twenty hours after the animal model was constructed, significant DVT started to form. Polymerase chain reaction tests showed that immediately after the model was created, the expression of IL-17 increased greatly, whereas the balance between t-PA and PAI-1 was disrupted just before DVT formed. The increase of serum IL-17 was positively related with the formation of DVT. Thus, the application of IL-17 monoclonal antibody could reduce the formation of DVT in rats. IL-17 might be a target for the early diagnosis of DVT and should be further studied to assess its clinical value.

The agreement between abnormal venous lactate and arterial lactate in the ED: a retrospective chart review.

INTRODUCTION: The evidence for prognostication using lactate is often based on arterial lactate (AL). Arterial sampling is painful and difficult, and carries risks. Studies comparing peripheral venous lactate (PVL) with AL showed little difference but predominantly included patients with normal lactate. The objective of this study was to measure agreement between PVL and AL in patients with elevated venous lactate. METHODS: This is a retrospective cross-sectional study. INCLUSION CRITERIA: ED patients age≥16, attending from October 2010 to June 2011 inclusive, with PVL≥2.0 mmol/L and AL taken within 1 hour. EXCLUSION CRITERIA: intravenous fluid prior to or between initial venous and arterial sampling. Primary endpoint: agreement between PVL and AL defined as mean difference±95% limits of agreement (LOA). The misclassification rate was assessed. RESULTS: N=232. VL median 3.50 mmol/L, range 2.00 to 15.00 mmol/L. AL median 2.45 mmol/L, range 1.0 to 13.2 mmol/L. The mean difference±SD between PVL and AL for all patients was 1.06±1.30 mmol/L (95%LOA -1.53 to 3.66 mmol/L). Using a cut-off of 2 mmol/L and 4 mmol/L, 36.2% and 17.9% of patients respectively were incorrectly classified as having elevated lactate. CONCLUSION: We report greater bias between VL and AL with broader LOA than previously documented. This may partly be due to the fact that we studied only patients with abnormal venous values, for whom close agreement would confer greatest clinical significance. The agreement between abnormal PVL and AL is poor and the high rate of misclassification may suggest that PVL is not a good substitute for AL if the venous lactate is abnormal.

Does venous blood gas analysis provide accurate estimates of hemoglobin oxygen affinity?

Alterations in hemoglobin oxygen affinity can be detected by exposing blood to different PO2 and recording oxygen saturation, a method termed tonometry. It is the gold standard to measure the PO2 associated with 50 % oxygen saturation, the index used to quantify oxygen affinity (P50Tono). P50Tono is used in the evaluation of patients with erythrocytosis suspected to have hemoglobin with abnormal oxygen affinity. Since tonometry is labor intensive and not generally available, we investigated whether accurate estimates of P50 could also be obtained by venous blood gas analysis, co-oximetry, and standard equations (P50Ven). In 50 patients referred for evaluation of erythrocytosis, pH, PO2, and oxygen saturation were measured in venous blood to estimate P50Ven; P50Tono was measured for comparison. Agreement among P50Ven and P50Tono was evaluated (Bland-Altman analysis). Mean P50Tono was 25.8 (range 17.4-34.1) mmHg. The mean difference (bias) of P50Tono-P50Ven was 0.5 mmHg; limits of agreement (95 % confidence limits) were -5.2 to +6.1 mmHg. The sensitivity and specificity of P50Ven to identify the 25 patients with P50Tono outside the normal range of 22.9-26.8 mmHg were 5 and 77 %, respectively. We conclude that estimates of P50 based on venous blood gas analysis and standard equations have a low bias compared to tonometry. However, the precision of P50Ven is not sufficiently high to replace P50Tono in the evaluation of individual patients with suspected disturbances of hemoglobin oxygen affinity.

Clinical validation of dried blood spot sampling in therapeutic drug monitoring of ciclosporin A in allogeneic stem cell transplant recipients: direct comparison between capillary and venous sampling.

BACKGROUND: The immunosuppressive drug ciclosporin A has a narrow therapeutic window and a large inter- and intraindividual pharmacokinetic variability. Therapeutic drug monitoring of ciclosporin is usually performed in ethylenediaminetetraacetic acid blood, obtained by venous sampling. Dried blood spot sampling (DBS) could be a useful alternative sampling method, which also easily allows multiple sampling, for example, for obtaining area under the curve. With DBS, capillary blood is obtained from a finger prick with an automatic lancet by the patients themselves, and the drop of blood is applied to sampling paper. This may limit the number and duration of hospital visits for these patients. METHODS: We describe a validation study in which venous and finger prick blood samples were collected at the same time. Venous sampling was performed by venipuncture, and the ethylenediaminetetraacetic acid blood samples were collected and stored at 4°C until analysis. Finger prick blood samples were collected using an automatic lancing device. The volume of the blood drops of patients was approximately 30 µL, and blood spots of about 10-mm diameter were produced. Paper disks with a diameter of 8 mm were punched out with an electromagnetic-driven hole puncher. DBS was compared with the routine assay in venous blood. The study population consisted of adult patients (18 years or older) who were treated with ciclosporin A and routinely monitored for adequate blood concentrations. RESULTS: Thirty-eight duplicate dried blood spots and venous samples were studied. Using weighted Deming regression, the slope was 1.01 with a standard error of 0.03 associated with an intercept of -9.0 (standard error = 5.9). These results indicate that there is no significant difference between the 2 sampling methods. For the medical decision level of 300 mcg/L, the bias was -4.7 mcg/L with a 95% confidence interval of -19.2 to 9.8 mcg/L. The Altman-Bland plot showed no difference between the 2 sampling methods. CONCLUSIONS: Our results demonstrate that DBS is a valid alternative for conventional venous sampling in allogeneic stem cell transplant recipients.