Relationship between free hemoglobin (hemolysis), potassium and ionized calcium in lithium heparin blood gas samples collected intraoperatively

OBJECTIVE

Develop sample acceptability rules by determining the relationship between free hemoglobin level (hemolysis) and potassium or ionized calcium in blood gas samples collected intraoperatively.

DESIGN AND METHODS

Hemolysis was assessed visually or by H index for lithium heparin blood gas samples collected intraoperatively. During periods one and three this was done using two different rules for visual assessment of centrifuged lithium heparin plasma. During period two H index was measured for all visually hemolyzed samples on a Roche Cobas c501 analyzer to determine acceptability. Potassium and ionized calcium were measured in 75 lithium heparin whole blood samples on a Radiometer ABL90 to correlate H index and potassium or ionized calcium.

RESULTS

During period one 35 of 5808 (0.6%) blood gas samples had visual hemolysis levels exceeding tolerance for reporting of potassium. By switching to measured H index using a laboratory-established threshold, during period 2 we estimate that 171 of 5396 (3.2%) blood gas samples exceeded the H index threshold for reporting of potassium. In 75 intraoperative blood gas samples with H index and whole blood potassium and ionized calcium measured; we observed no relationship between H index and potassium or ionized calcium. During period 3 we switched to visual assessment of hemolysis with a greater tolerance for hemolysis; with only 3 of 5345 (0.06%) samples exceeding the new visual hemolysis threshold.

CONCLUSION

For blood gas samples collected intraoperatively, there is no relationship between hemolysis and measured potassium or ionized calcium. The results suggest that only grossly hemolyzed intraoperative blood gas samples should be rejected for measurement of whole blood potassium and ionized calcium.

High-Sensitivity Troponin in Patients With Coronary Artery Endothelial Dysfunction

BACKGROUND

Coronary endothelial dysfunction (CED) is associated with recurrent ischemia. The role of high-sensitivity cardiac troponin I (hscTnI) levels in patients with CED has not been established.

METHODS

Patients with suspected ischemia, who underwent clinically indicated coronary angiography and were found to have non-obstructive coronary artery disease, were included in the study. CED was defined as ≤50% increase in coronary blood flow from baseline and/or a decrease in epicardial coronary artery diameter >20% in response to maximal dosages of acetylcholine. HscTnI was measured at the time of the procedure using the Architect hscTnI assay (Abbott).

RESULTS

Of 299 patients, 60 had normal endothelial function and 239 patients had abnormal endothelial function. The median age of the population was 52 years (interquartile range [IQR], 45-60 years). Patients with abnormal endothelial function had significantly higher log hscTnI values when compared to patients with normal endothelial function (0.9 ng/L [IQR, 0.7-1.4 ng/L] vs 0.7 ng/L [IQR, 0.7-1.1 ng/L]; P=.04). An hscTnI value >12.5 ng/L was 100% specific for the presence of endothelial dysfunction (100% positive predictive value). There were 39 major adverse cardiovascular events during follow-up. In patients with normal endothelial function, hscTnI levels were significantly higher in patients who developed major adverse cardiac events when compared to patients who did not (1.35 ng/L [IQR, 1.1-2.1 ng/L] vs 0.7 ng/L [IQR, 0.7-1.1 ng/L]; P=.02).

CONCLUSION

Our findings suggest that endothelial dysfunction may be associated with higher baseline hscTnI levels, suggesting increased myocardial injury in this population of patients. Additional studies are necessary to further define the role of hscTnI in risk stratification in this population.

Blood gas sample spiking with total parenteral nutrition, lipid emulsion, and concentrated dextrose solutions as a model for predicting sample contamination based on glucose result

OBJECTIVE

Evaluate the effects of blood gas sample contamination with total parenteral nutrition (TPN)/lipid emulsion and dextrose 50% (D50) solutions on blood gas and electrolyte measurement; and determine whether glucose concentration can predict blood gas sample contamination with TPN/lipid emulsion or D50.

DESIGN AND METHODS

Residual lithium heparin arterial blood gas samples were spiked with TPN/lipid emulsion (0 to 15%) and D50 solutions (0 to 2.5%). Blood gas (pH, pCO2, pO2), electrolytes (Na+, K+ ionized calcium) and hemoglobin were measured with a Radiometer ABL90. Glucose concentration was measured in separated plasma by Roche Cobas c501. Chart review of neonatal blood gas results with glucose >300 mg/dL (>16.65 mmol/L) over a seven month period was performed to determine whether repeat (within 4 h) blood gas results suggested pre-analytical errors in blood gas results. Results were used to determine whether a glucose threshold could predict contamination resulting in blood gas and electrolyte results with greater than laboratory-defined allowable error.

RESULTS

Samples spiked with 5% or more TPN/lipid emulsion solution or 1% D50 showed glucose concentration >500 mg/dL (>27.75 mmol/L) and produced blood gas (pH, pO₂, pCO₂) results with greater than laboratory-defined allowable error. TPN/lipid emulsion, but not D50, produced greater than allowable error in electrolyte (Na⁺,K⁺,Ca⁺⁺,Hb) results at these concentrations. Based on chart review of 144 neonatal blood gas results with glucose >250 mg/dL received over seven months, four of ten neonatal intensive care unit (NICU) patients with glucose results >500 mg/dL and repeat blood gas results within 4 h had results highly suggestive of pre-analytical error. Only 3 of 36 NICU patients with glucose results 300-500 mg/dL and repeat blood gas results within 4 h had clear pre-analytical errors in blood gas results.

CONCLUSION

Glucose concentration can be used as an indicator of significant blood sample contamination with either TPN/lipid emulsion or D50 solution. NICU blood gas samples with glucose ≥300 mg/dL should be considered potentially contaminated, and samples with glucose >500 mg/dL have a risk for contamination.

Defining the limitations of transcutaneous bilirubin measurement in late preterm newborns

OBJECTIVE

The objective of this study is to determine the impact of postnatal age on the bias between transcutaneous (TcB) and total serum bilirubin (TSB), and evaluate a TcB screening protocol.

STUDY DESIGN

Preterm and term infants had paired TcB and TSB performed on days 1 to 3 of life; a subset of preterm infants had measurements on days 4 to 7. Sensitivity and specificity of TcB (plotted on an age-specific TSB nomogram) for prediction of high-intermediate (HIR) or high-risk TSB were calculated.

RESULTS

Median TcB bias was 2.6 and 2.5 mg dl^-1 for term and preterm infants in the first 3 days of life, respectively. However, median bias was 2.2 mg dl^-1 for preterm infants at 4 to 7 days of life. TcB in preterm infants predicted HIR or high-risk TSB with 94% sensitivity and 56% specificity.

CONCLUSION

TcB screening protocols developed for term infants can be used for late preterm infants in the first 3 days of life.

Neonatal Intensive Care Unit Quality Initiative: Identifying Preanalytical Variables Contributing to Specimen Hemolysis and Measuring the Impact of Evidence-Based Practice Interventions

OBJECTIVES

Blood specimen hemolysis is a major cause of sample recollection in the neonatal intensive care unit. We aimed to reduce the hemolysis rate from 6.3% at baseline to less than 4% within the 9 months' duration of the study.

METHODS

Intravenous infusion of lipid emulsion during sample collection, sample collection site, and blood sample transportation methods were investigated as possible contributors to hemolysis. Subsequently, two practice improvements were implemented: pausing lipid emulsion infusion prior to collection and slowing withdrawal rates through arterial catheters.

RESULTS

Samples were more likely to be hemolyzed if they were collected during lipid infusion and subsequently transported by pneumatic tube or collected through an arterial catheter. Retrospective analysis demonstrated a decreased number of tests cancelled due to specimen hemolysis (3.5%) after our interventions.

CONCLUSIONS

We identified three variables contributing to hemolysis and instituted two clinical practice interventions to significantly reduce test cancellations due to hemolysis.

Implementation of Clinical Decision Support Rules to Reduce Repeat Measurement of Serum Ionized Calcium, Serum Magnesium, and N-Terminal Pro-B-Type Natriuretic Peptide in Intensive Care Unit Inpatients

BACKGROUND

We assessed the impact of clinical decision support (CDS) rules within the electronic health record for ionized calcium (iCa), serum magnesium (Mg), and N-terminal pro-B-type natriuretic peptide (NT-proBNP) in intensive care unit (ICU) inpatients at a large academic center.

METHODS

A repeat order for measurement of iCa or Mg placed within 24 (iCa) or 48 (Mg) h of a previously nonactionable result, or additional orders for NT-proBNP beyond 1 within a single hospitalization, triggered a CDS pop-up alert showing the prior result and offering the opportunity to cancel the order or to place the order after entering an indication for repeat testing. The number of tests performed for each of these analytes and incidence of adverse clinical outcomes potentially associated with hypocalcemia or hypomagnesemia were compared between the 90-day period before CDS implementation and two 90-day periods immediately following.

RESULTS

iCa test volumes decreased by 48%, Mg by 39%, and NT-proBNP by 28% in the 90-day period immediately following implementation and remained decreased by 54%, 49%, and 22%, respectively, during the following 90-day period (all P values <0.0002). Adverse clinical outcomes potentially associated with hypocalcemia or hypomagnesemia did not increase (all P-values >0.17).

CONCLUSIONS

Implementation of CDS dramatically decreased repeat testing of iCa, Mg, and NT-proBNP without adversely impacting clinical outcomes in the ICU. Expansion of the rules from the ICU units to include the entire hospitalized patient population and expansion to additional analytes is expected to lead to further reductions in testing.

Relation of Activated Clotting Times During Percutaneous Coronary Intervention to Outcomes

Monitoring anticoagulation using the activated clotting time (ACT) in patients treated with heparin and undergoing percutaneous coronary intervention (PCI) is one of the most frequently used tests in invasive cardiology. However, despite its widespread use and guideline endorsement, uncertainty remains regarding the association of ACT with outcomes in contemporary practice. We reviewed all PCI procedures performed at the Mayo Clinic (Rochester, Minnesota) from October 2001 to December 2012 and evaluated the association between the ACT before device activation and in-hospital and 1-year outcomes. ACT values were grouped into tertiles for descriptive purposes and analyzed as a continuous variable for assessment of outcomes. We used logistic and Cox proportional hazards regression models to estimate the association of ACT and outcomes. Of the 12,055 patients who underwent PCI with an ACT value before device activation, 3,977 (33.0%) had an ACT <227, 4,046 (33.6%) had an ACT 227 to 285, and 4,032 (33.4%) had an ACT >285. Baseline and procedural characteristics were similar across ACT tertiles. In unadjusted analysis, higher ACT values were associated with death (p <0.001), bleeding (p = 0.024), procedural complication (p <0.001), and higher 1-year events (cardiac death, p <0.001; cardiac death/myocardial infarction, p = 0.022). After multivariable adjustment for baseline and procedural characteristics, ACT was not independently associated with in-hospital or 1-year ischemic, thrombotic, or bleeding outcomes. In conclusion, ACT values before device activation are not independently associated with clinically important outcomes in contemporary PCI practice.

Impact of Glucose Meter Error on Glycemic Variability and Time in Target Range During Glycemic Control After Cardiovascular Surgery

BACKGROUND

We retrospectively studied the impact of glucose meter error on the efficacy of glycemic control after cardiovascular surgery.

METHOD

Adult patients undergoing intravenous insulin glycemic control therapy after cardiovascular surgery, with 12-24 consecutive glucose meter measurements used to make insulin dosing decisions, had glucose values analyzed to determine glycemic variability by both standard deviation (SD) and continuous overall net glycemic action (CONGA), and percentage glucose values in target glucose range (110-150 mg/dL). Information was recorded for 70 patients during each of 2 periods, with different glucose meters used to measure glucose and dose insulin during each period but no other changes to the glycemic control protocol. Accuracy and precision of each meter were also compared using whole blood specimens from ICU patients.

RESULTS

Glucose meter 1 (GM1) had median bias of 11 mg/dL compared to a laboratory reference method, while glucose meter 2 (GM2) had a median bias of 1 mg/dL. GM1 and GM2 differed little in precision (CV = 2.0% and 2.7%, respectively). Compared to the period when GM1 was used to make insulin dosing decisions, patients whose insulin dose was managed by GM2 demonstrated reduced glycemic variability as measured by both SD (13.7 vs 21.6 mg/dL, P < .0001) and CONGA (13.5 vs 19.4 mg/dL, P < .0001) and increased percentage glucose values in target range (74.5 vs 66.7%, P = .002).

CONCLUSIONS

Decreasing glucose meter error (bias) was associated with decreased glycemic variability and increased percentage of values in target glucose range for patients placed on intravenous insulin therapy following cardiovascular surgery.

Agreement between whole blood and plasma sodium measurements in profound hyponatremia

OBJECTIVES

We compared two different methods of whole blood sodium measurement to plasma sodium measurement using samples in the profoundly hyponatremic range (Na < 120 mmol/L).

DESIGN AND METHODS

Whole blood pools with a range of low sodium values were generated using combinations and dilutions of pooled electrolyte-balanced lithium heparin samples submitted for arterial blood gas analysis. Each pool was analyzed five times on a Radiometer 827 blood gas analyzer and iSTAT analyzer. Pools were centrifuged to produce plasma, which was analyzed five times on a Roche Cobas c501 chemistry analyzer. An additional 40 fresh (analyzed on day of collection) excess lithium heparin arterial blood gas samples from 36 patients were analyzed on the Radiometer 827, iSTAT, and Cobas c501 as described above. The setting was a tertiary referral center. Blood samples were collected from a combination of patients in the intensive care unit, operating theaters and emergency room.

RESULTS

All methods demonstrated excellent precision, even in the profoundly hyponatremic measurement range (Na < 120 mmol/L using a plasma reference method). However, agreement between the methods varied with the degree of hyponatremia. In the profoundly hyponatremic range, Radiometer whole blood sodium values were nearly identical to plasma reference sodium, while iSTAT whole blood sodium showed a consistent positive bias relative to plasma sodium in this range.

CONCLUSION

If whole blood direct sodium measurements are compared with plasma sodium in profoundly hyponatremic patients consideration should be given to the use of Radiometer blood gas analyzers over iSTAT since the latter shows a positive bias relative to a plasma comparative method.

Precision and Reliability of 5 Platelet Function Tests in Healthy Volunteers and Donors on Daily Antiplatelet Agent Therapy

BACKGROUND

Anticoagulation protocols used during mechanical circulatory support call for titration of antiplatelet agents. We compared the precision and reliability of 5 platelet function tests in healthy volunteers and donors on daily antiplatelet therapy to distinguish their efficacy for titrating antiplatelet therapy.

METHODS

We assessed arachidonic acid–induced platelet function by light transmission aggregometry (LTA), Multiplate impedance aggregometry, VerifyNow, and platelet mapping by thromboelastography (TEG PM). We assessed ADP-induced platelet function by the same methods and flow cytometry. Forty healthy volunteers and 10–13 volunteers on daily aspirin and/or clopidogrel therapy were evaluated. We compared tests for intraassay precision, interassay precision (samples from 2 separate blood draws), and reliability coefficient.

RESULTS

For arachidonic acid–induced platelet aggregation in healthy volunteers, intra- and interassay CVs were ≤10% for all methods. Intra- and interassay precision among donors on daily aspirin was ≤30% for all methods except LTA (38% interassay CV) and TEG PM (95% intraassay and 104% interassay CV). For ADP-induced platelet function, intra- and interassay precision was ≤10% and ≤30% for all methods. Only Multiplate demonstrated moderate or greater (R &gt; 0.40) reliability coefficients for arachidonic acid–induced platelet function among all subjects. All methods of ADP-induced platelet function, except TEG PM, demonstrated substantial or greater (R &gt; 0.60) reliability among all subjects.

CONCLUSIONS

TEG PM is least suited to monitor effects of antiplatelet agents. Multiplate impedance aggregometry was the only method to demonstrate an acceptable reliability coefficient among healthy volunteers and donors on both aspirin and clopidogrel therapy.

Retrospective evaluation of the accuracy of Roche AccuChek Inform and Nova StatStrip glucose meters when used on critically ill patients

BACKGROUND

More stringent accuracy guidelines for hospital-use glucose meters have recently been published, but it remains unclear whether glucose meters can meet these accuracy guidelines when measurement is performed on critically ill patients with fresh whole blood samples.

MATERIALS AND METHODS

We performed a retrospective evaluation of a conventional (Roche Diagnostics [Indianapolis, IN] AccuChek® Inform) and a newer-generation (Nova Biomedical [Waltham, MA] StatStrip®) glucose system by comparing paired (drawn within 5 min of each other) whole blood glucose meter and laboratory serum glucose values obtained from intensive care unit (ICU) patients. We also performed a prospective evaluation of the accuracy of the Nova StatStrip.

RESULTS

The median (interquartile range) bias between Roche AccuChek Inform and serum laboratory glucose measurements was 11 (6-18) mg/dL, compared with a median bias between the Nova StatStrip and serum glucose measurements of 1 (-5 to 5) mg/dL. StatStrip met International Organization for Standardization 15197 and Clinical and Laboratory Standards Institute (CLSI) POCT12-A3 accuracy guidelines using both retrospective and prospective datasets.

CONCLUSIONS

The newer-generation (StatStrip) glucose meter met more stringent CLSI POCT12-A3 accuracy criteria because of reduced bias compared with the previous-generation device. Reduced glucose meter bias led to fewer insulin dosing discrepancies when the insulin dose determined from serum glucose was compared with that determined from the glucose meter value using the institutional glycemic control protocol.

Development and initial validation of a project-based rubric to assess the systems-based practice competency of residents in the clinical chemistry rotation of a pathology residency

CONTEXT

Systems-based practice (SBP) is 1 of 6 core competencies required in all resident training programs accredited by the Accreditation Council for Graduate Medical Education. Reliable methods of assessing resident competency in SBP have not been described in the medical literature.

OBJECTIVE

To develop and validate an analytic grading rubric to assess pathology residents' analyses of SBP problems in clinical chemistry.

DESIGN

Residents were assigned an SBP project based upon unmet clinical needs in the clinical chemistry laboratories. Using an iterative method, we created an analytic grading rubric based on critical thinking principles. Four faculty raters used the SBP project evaluation rubric to independently grade 11 residents' projects during their clinical chemistry rotations. Interrater reliability and Cronbach α were calculated to determine the reliability and validity of the rubric. Project mean scores and range were also assessed to determine whether the rubric differentiated resident critical thinking skills related to the SBP projects.

RESULTS

Overall project scores ranged from 6.56 to 16.50 out of a possible 20 points. Cronbach α ranged from 0.91 to 0.96, indicating that the 4 rubric categories were internally consistent without significant overlap. Intraclass correlation coefficients ranged from 0.63 to 0.81, indicating moderate to strong interrater reliability.

CONCLUSIONS

We report development and statistical analysis of a novel SBP project evaluation rubric. The results indicate the rubric can be used to reliably assess pathology residents' critical thinking skills in SBP.

Empiric validation of simulation models for estimating glucose meter performance criteria for moderate levels of glycemic control

BACKGROUND

We used simulation modeling to relate glucose meter performance criteria to insulin dosing errors for patients on a moderate glycemic control protocol (glucose target, 110-150 mg/dL) and empirically validated assumptions from simulation models using observed glucose meter and laboratory glucose values obtained nearly simultaneously.

SUBJECTS AND METHODS

The 25,948 glucose values from 1,513 patients on a moderate glycemic control protocol were used to represent the expected distribution of glucose values in this patient population. Simulation models were used to relate glucose meter analytical performance to insulin dosing errors assuming 10%, 15%, or 20% total allowable error (TEa). In addition, 4,017 paired glucose meter and serum laboratory glucose measurements drawn within 5 min of each other were used to generate an empiric dataset to validate simulation model assumptions relating glucose meter performance to insulin dosing errors.

RESULTS

Large (three or more category) insulin dosing errors are predicted to occur only under the 20% TEa condition. Two category insulin dosing errors were common (6-20% of all insulin dosing decisions) when 20% TEa was assumed, but frequency decreased to only 0.2% of dosing decisions when 10% TEa was modeled. When insulin dosing error rates were measured empirically by comparing paired glucose meter and laboratory glucose values, insulin dosing error rates were very similar to those predicted for the 20% TEa condition.

CONCLUSIONS

Both simulation models and empiric data demonstrate that glucose meters that perform at ≥20% TEa allow large insulin dosing errors during a moderate glycemic control protocol.

Fresh and citrated whole-blood specimens can produce different thromboelastography results in patients on extracorporeal membrane oxygenation

OBJECTIVES

To compare thromboelastography (TEG) tracings obtained from fresh and citrated whole-blood samples in patients on extracorporeal membrane oxygenation (ECMO) or after cardiopulmonary bypass and in healthy volunteers.

METHODS

Samples of fresh and citrated whole blood were analyzed for 25 patients and 4 healthy volunteers. Thromboelastography analysis was performed in both plain and heparinase cups.

RESULTS

In 5 of 6 patients on ECMO, use of citrated samples resulted in apparent partial or complete heparin reversal. In TEG tracings from patients following cardiopulmonary bypass, there was a slight hypercoagulable appearance in the citrated sample. No differences were noted between fresh and citrated samples from healthy volunteers whose blood was spiked with heparin.

CONCLUSIONS

In some patients on ECMO, use of samples collected in sodium citrate tubes for TEG analysis results in significant artifacts, which could lead to heparin overdosing in these patients.

Analytical performance of three point of care methods for pleural fluid pH analysis

OBJECTIVE

The performance of three point of care methods for pleural fluid pH analysis was compared to a currently validated blood gas analyzer.

DESIGN AND METHODS

An ABL 725 (Radiometer America, Westlake, OH) was used as the reference method to evaluate three cartridge-based assays: ABL 90 FLEX (Radiometer), and i-STAT 1 (Abbott Point of Care, Abbott Park, IL) CG4+ and G3+ cartridges for pleural fluid pH analysis. Pooled residual pleural fluid samples and quality control material were analyzed to determine intra- and inter-assay precision. Method comparison was performed with spiked (n=40) and clinically-ordered (n=10) pleural fluid samples across the analytical measuring range.

RESULTS

All methods demonstrated inter-assay CVs<0.1% at pH values of 7.1 and 7.6, and intra-assay CVs<0.3% at pH values of 7.2 and 7.7. Bland-Altman plots demonstrated clinically significant bias between ABL 725 and each cartridge-based method only at pH>7.6. For samples with pH<7.6 mean bias vs. ABL 725 was -0.01 for ABL 90 FLEX and 0.03 for i-STAT 1 CG4+ and G3+ cartridges. Clinical concordance using a decision limit of pH7.2 was 96-98% for the three methods.

CONCLUSIONS

Analytical and clinical performance of the three cartridge-based methods was comparable to a validated blood gas analyzer for pleural fluid pH analysis. Cartridge-based pH methods offer the advantage of easier troubleshooting for clots and clogs as they use disposable electrodes. However cartridge-based methods are not currently FDA-approved for pleural fluid samples, such that additional validation would be required for this specimen type.

Temporal sequence of major biochemical events during blood bank storage of packed red blood cells

BACKGROUND

We used sensitive spectroscopic techniques to measure changes in Band 3 oligomeric state during storage of packed red blood cells (RBC); these changes were compared to metabolic changes, RBC morphology, cholesterol and membrane protein loss, phospholipid reorganisation of the RBC membrane, and peroxidation of membrane lipid. The aim of the study was to temporally sequence major biochemical events occurring during cold storage, in order to determine which changes may underlie the structural defects in stored RBC.

MATERIALS AND METHODS

Fifteen RBC units were collected from normal volunteers and stored under standard blood bank conditions; both metabolic changes and lipid parameters were measured by multiple novel assays including a new mass spectrometric measurement of isoprostane (lipid peroxidation) and flow cytometric assessment of CD47 expression. Band 3 oligomeric state was assessed by time-resolved phosphorescence anisotropy, and RBC morphology by microscopy of glutaraldehyde-fixed RBC.

RESULTS

Extracellular pH decreased and extracellular potassium increased rapidly during cold storage. Band 3 on the RBC membrane aggregated into large oligomers early in the storage period and coincident with changes in RBC morphology. Membrane lipid changes, including loss of unesterified cholesterol, lipid peroxidation and expression of CD47, also changed early during the storage period. In contrast loss of acetylcholinesterase activity and haemolysis of RBC occurred late during storage.

DISCUSSION

Our results demonstrate that changes in the macromolecular organisation of membrane proteins on the RBC occur early in storage and suggest that lipid peroxidation and/or oxidative damage to the membrane are responsible for irreversible morphological changes and loss of function during red cell storage.

BD rapid serum tubes reduce false positive plasma troponin T results on the Roche Cobas e411 analyzer

OBJECTIVES

In an attempt to reduce false positive results and improve turnaround time, we investigated the BD Rapid Serum Tube as an alternate sample type to lithium heparin plasma for Roche Troponin T analysis on the Roche Cobas e411 analyzer.

DESIGN AND METHODS

BD Plasma Separator Tubes (PST) and Rapid Serum Tubes (RST) were collected in tandem from Emergency Department patients who had clinical orders for Troponin T over a 1 month period.

RESULTS

RST and PST samples yielded analytically and clinically concordant Troponin T results on the Roche Cobas e411. Rare false positive results in lithium heparin samples were not observed with rapid clot serum tubes.

CONCLUSIONS

RST samples are appropriate for stat Troponin T analysis, and appear to reduce the incidence of rare false positive Troponin T results obtained with lithium heparin samples.

Accuracy of neonatal transcutaneous bilirubin measurement in the outpatient setting

OBJECTIVE. To evaluate the effectiveness of transcutaneous bilirubin (TcB) measurement in predicting risk for neonatal hyperbilirubinemia in outpatients. DESIGN. Subjects were infants ≤8 days old seen in an outpatient clinic. Infants discharged with high-risk (HR) or high-intermediate risk (HIR) total serum bilirubin (TSB) values and jaundiced infants were recruited. TSB and TcB (BiliChek) levels were plotted on an hour-specific nomogram to determine risk for hyperbilirubinemia. RESULTS. A total of 79 infants provided 87 sets of TcB and TsB values. Mean bias and standard deviation between TcB and TsB was 1.5 ± 2.1 mg/dL for outpatients, compared with 2.7 ± 1.3 mg/dL for inpatients. The sensitivity and specificity of HR or HIR TcB for predicting an HR or HIR TSB were 87% and 58%, respectively. Of 9 infants readmitted for phototherapy, 1 had a low-risk TcB and high-risk TSB. CONCLUSIONS. TcB screening in the outpatient environment may not be safe and efficient.