Audit Exposes Flawed Blood Sampling for “Digoxin Levels”
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Therapeutic “digoxin level” monitoring in selected wards was audited. Time elapsing between the last dose and blood sampling was considered appropriate if ≥6 h. If such details were not entered on the requisition, the maximum time elapsing was estimated as “appropriate” or “inappropriate” from the time samples were logged into the laboratory and the time the last dose was entered in the patient's treatment sheet. In 22 requisitions detailing sampling time, nine were considered inappropriate. In an additional 150 instances, timing was estimated as inappropriate in 45. Among the 118 requests where timing (estimated or labelled) was appropriate, available plasma digoxin concentrations yielded a mean of 1.0 nM, compared to 1.6 nM in the corresponding 54 patients with premature sampling; this difference was both clinically and statistically significant (95% confidence limits 0.8–1.2 and 1.3–1.9 nM, respectively, p < 0.001). Premature blood sampling for digoxin levels was common and associated with higher concentrations than when appropriate. Such inappropriate timing may not have serious consequences, but digoxin levels area matter of record and are used for teaching; due attention to timing could provide more reliable information and avoid wasting valuable resources.Keywords:
Requisition
Blood sampling
Therapeutic Drug Monitoring
Venous blood
Objective It was aimed to objectively evaluate the effects of using disposable automatic venous hemostix and syringe blood sampling on blood rheology. Methods 30 patients who suffering from different diseases and needed to have blood rheology tested were enrolled in our study. Each patient had two venous blood samplings randomly, one with a disposable automatic venous blood sampler and the other with syringe injection. The parameters of high shear and low shear whole blood viscosity (200/s and 3/s), plasma viscosity, hematocrit and fibrinogen were determined. Results The parameters of low shear whole blood viscosity and plasma viscosity were significantly higher ( P 0. 05 ) with syringe injection compared with disposable automatic venous blood sampler sampling. Conclusion The effect of using a disposable automatic venous blood sampler on blood rheology was smaller than that of syringe injection,and we suggest popularizing it as a substitute of injection for blood sampling.
Blood sampling
Venous blood
Syringe driver
Hemorheology
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Therapeutic drug monitoring (TDM) of the antiepileptic drug valproic acid (VPA) is recommended in patients with multiple drug therapy or with concomitant disabilities to ensure treatment efficacy and avoid adverse reactions in both adults and children. The use of sampling techniques compatible with home sampling, such as dried blood spot sampling could potentially facilitate this for patients. AIM. To assess the usefulness of a bioanalytical method for quantification of VPA in dried blood spots.Quantification was based on liquid chromatography-mass spectrometry (LC-MS), both for the DBS method and the plasma-based reference method.The method was validated in the range 10-1200 μmol/L. Total imprecision ranged from 4.9-8.9 (%CV) and accuracy was within ± 14%.The validated method has potential for evaluation in therapeutic drug monitoring in combination with home sampling of DBS. The impact of spot size can be controlled through acceptance criteria and hematocrit in the range 30-60% can be accepted in sampling. Comparison of VPA levels between plasma and whole blood cannot be done without considering the blood-plasma ratio.
Valproic Acid
Dried blood
Spots
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Digoxin remains a commonly prescribed medication for the treatment of congestive cardiac failure or atrial tachyarrhythmias. Its utility is offset by its narrow therapeutic index requiring regular blood concentration monitoring. Recent evidence suggests that a lower therapeutic range (0.5- 0.8 mg/L, or 0.6-1.0 nmol/L) is associated with reduced mortality in patients with congestive cardiac failure. Therapeutic drug monitoring for digoxin is carried out by immunoassays that are well established in routine clinical practice. Laboratories using different immunoassays may be involved in monitoring individual patients throughout the protracted course of therapy. These results should be concordant to ensure consistent dose individualization and optimum clinical management. We have investigated the discordance in digoxin measurements involving five different laboratories across the Adelaide metropolitan area.Aliquots from routine digoxin samples (n = 261) were analysed by accredited laboratories using commercially available immunoassays.The results showed that 119 (46%) of 261 samples were so varied that a different clinical outcome was indicated when reviewed by the treating physician. The differences between the highest and lowest readings from any one sample were also substantial, with 45% of the measurements exceeding 0.3 microg/L.Our study shows the considerable variation in the routine monitoring of digoxin. This makes therapeutic drug monitoring difficult to interpret and complicates clinical management when treating physicians are endeavouring to avoid toxicity and optimize dosing. These results raise a significant concern for the quality of therapeutic drug monitoring of digoxin and have direct repercussions on patient care.
Therapeutic Drug Monitoring
Therapeutic index
Clinical Practice
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Venous blood
Blood sampling
Incremental exercise
Exercise intensity
Intensity
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Blood osmolality is considered the gold standard hydration assessment, but has limited application for technical and invasive reasons. Paired antecubital-venous blood and fingertip-capillary blood were collected pre- and 30 min post-drinking 600 mL water in 55 male/female participants. No bias (0.2 mOsmo/kg, limits of agreement = -2.5 to 2.8 mOsmo/kg) was found between sampling methods, with high linear correlation (Spearman's
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Gold standard (test)
Plasma osmolality
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Digoxin is an important drug in the treatment of patients with either congestive heart failure or atrial arrhythmia. Because of its narrow therapeutic range, digoxin serum concentrations are commonly monitored in both inpatients and outpatients. However, with the costs of health care skyrocketing, there is debate whether such therapeutic drug monitoring (TDM) is cost-effective. To reduce the number of samples drawn too soon after a previous dose and in an effort to improve digoxin TDM at this teaching hospital, a new dosing and monitoring policy was initiated. This policy involved uniform digoxin dosing at 5 p.m. (1700 h) for all inpatients and serum drug measurements at 7 a.m. (0700 h) the next day. By coordinating the time of dosing to be greater than 12 h prior to serum digoxin analysis, the number of inappropriate digoxin serum determinations have been reduced. This new protocol has increased the effectiveness of the toxicology laboratory and enhanced the efficiency of the house staff. Other issues concerning digoxin TDM are also addressed. These findings can be generalized to all drugs that are monitored at any hospital and can result in a significant cost savings and decrease the time spent analyzing inappropriate data.
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Serum concentration
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This review provides an overview on the current applications of dried blood spots (DBS) as matrices for therapeutic drug (TDM) and drug or disease response monitoring (DRM). Compared with conventional methods using plasma/serum, DBS offers several advantages, including minimally invasiveness, a small blood volume requirement, reduced biohazardous risk, and improved sample stability. Numerous assays utilising DBS for TDM have been reported in the literature over the past decade, covering a wide range of therapeutic drugs. Several factors can affect the accuracy and reliability of the DBS sampling method, including haematocrit (HCT), blood volume, sampling paper and chromatographic effects. It is crucial to evaluate the correlation between DBS concentrations and conventional plasma/serum concentrations, as the latter has traditionally been used for clinical decision. The feasibility of using DBS sampling method as an option for home-based TDM is also discussed. Furthermore, DBS has also been used as a matrix for monitoring the drug or disease responses (DRM) through various approaches such as genotyping, viral load measurement, assessment of inflammatory factors, and more recently, metabolic profiling. Although this research is still in the development stage, advancements in technology are expected to lead to the identification of surrogate biomarkers for drug treatment in DBS and a better understanding of the correlation between DBS drug levels and drug responses. This will make DBS a valuable matrix for TDM and DRM, facilitating the achievement of pharmacokinetic and pharmacodynamic correlations and enabling personalised therapy.
Therapeutic Drug Monitoring
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Dried blood spot
Dried blood
Pharmacodynamics
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The purpose of this study is validation of calibrating a standard input function in autoradiography (ARG) method by one point venous blood sampling as a substitute for that by one point arterial blood sampling. Ten and 20 minutes after intravenous constant infusion of 123I-IMP, arterialized venous blood sampling from a dorsal vein were performed on 15 patients having ischemic cerebrovascular disease. And arterial blood sampling from radial artery was performed 10 min after 123I-IMP infusion. The mean difference rates of integrated input function between calibrated standard input function by arterial blood sampling at 10 min and that by venous blood sampling were 4.1 +/- 3% and 9.3 +/- 5.4% at 10 and 20 min after 123I-IMP infusion, respectively. The ratio of venous blood radioactivity to arterial blood radioactivity at 10 min after 123I-IMP infusion was 0.96 +/- 0.02. There was an excellent correlation between ARG method CBF values obtained by arterial blood sampling at 10 min and those obtained by arterialized venous blood sampling at 10 min. In conclusion, a substitution by arterialized venous blood sampling from dorsal hand vein for artery can be possible. The optimized time for arterialized venous blood sampling was 10 min after 123I-IMP infusion.
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Blood sampling
Arterial blood
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What is the central question of this study? Glucagon-like peptide-1 (GLP-1) is an important obesity/diabetes target, with effects dependent on circulating GLP-1 concentrations. Peripheral tissues extract GLP-1; therefore, sampling venous versus arterialized blood might provide different GLP-1 concentrations. This study examined whether arterialization alters GLP-1 concentrations during fasting and feeding. What is the main finding and its importance? This study demonstrates that venous blood provides lower postprandial but not fasting GLP-1 concentrations versus arterialized blood. Therefore, when accurate assessment of postprandial peripheral availability of GLP-1 is required, blood sampling methods should be considered carefully, reported clearly, and arterialization is recommended.Glucagon-like peptide-1 (GLP-1) displays concentration-dependent effects on metabolism, appetite and angiogenesis; therefore, accurate determination of circulating GLP-1 concentrations is important. In this study, we compared GLP-1 concentrations in venous versus arterialized blood in both fasted and fed conditions. Venous and arterialized blood samples were obtained simultaneously from 10 young, healthy men before and 30, 60 and 120 min after ingestion of 75 g glucose. Plasma GLP-1 concentrations increased in response to glucose ingestion (time effect, P < 0.01) and to a lesser extent in venous versus arterialized plasma (time × arterialization interaction, P < 0.01). Accordingly, the plasma incremental area under the curve was lower in venous versus arterialized plasma (974 ± 88 versus 1214 ± 115 pmol l (120 min)-1 , respectively, P = 0.049). In the postprandial state, there was a positive relationship between arterialized GLP-1 concentrations and the venous-arterialized difference in GLP-1 concentrations (r2 = 0.51; P < 0.01). Both arterialized and venous peak GLP-1 concentrations showed positive relationships with peak arterialized insulin concentrations (both r2 > 0.6, P < 0.01). Venous sampling results in lower concentrations of GLP-1 in the postprandial but not the fasted state compared with arterialized blood. This absolute difference is biologically meaningful and is magnified when GLP-1 availability is high. Therefore, sampling from arterialized blood may provide a better chance of detecting small differences in postprandial GLP-1 availability with interventions. If absolute GLP-1 concentrations are of interest, the blood sampling method should be considered carefully and reported clearly.
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Blood sampling
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Accurate arterial blood gas (ABG) analysis is essential in the management of patients with hypercapnic respiratory failure, but repeated sampling requires technical expertise and is painful. Missed sampling is common and has a negative impact on patient care. A newer venous to arterial conversion method (v-TAC, Roche) uses mathematical models of acid-base chemistry, a venous blood gas sample and peripheral blood oxygen saturation to calculate arterial acid-base status. It has the potential to replace routine ABG sampling for selected patient cohorts. The aim of this study was to compare v-TAC with ABG, capillary and venous sampling in a patient cohort referred to start non-invasive ventilation (NIV).
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Blood sampling
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