Peritoneal and Pleural Fluid Chemistry Measurements Performed on Three Chemistry Platforms

BACKGROUND

Chemistry testing is requested for body fluid (BF) specimens despite the lack of assays approved by the US Food and Drug Administration (FDA). The criteria for categorizing fluids as transudate or exudate are not validated across analyzers.

OBJECTIVE

To compare BF chemical analysis and classification by different analyzers.

METHODS

We analyzed 10 pleural and 18 peritoneal fluids with corresponding plasma specimens using the Vitros 5,1 FS; Abbott ARCHITECT ci8200; and Roche Modular P platforms. Total protein (TP) and lactate dehydrogenase (LDH) were measured for pleural fluids. Light's criteria were applied. Albumin was measured for peritoneal specimens, and the plasma-ascites-albumin gradient was calculated.

RESULTS

TP results showed agreement. The Vitros LDH assay produced higher fluid:plasma ratios. Classification by Light's criteria resulted in 1 discrepancy (ARCHITECT). Albumin results showed agreement. There were 2 discrepant gradient interpretations (Vitros).

CONCLUSIONS

These data suggest that analyses of pleural and peritoneal fluids using these platforms are diagnostically interchangeable.

Method Verification Shows a Negative Bias between 2 Procalcitonin Methods at Medical Decision Concentrations

BACKGROUND

Procalcitonin (PCT) concentration increases as a result of systemic inflammation owing to bacterial infection. Many PCT algorithms and medical decision concentrations (MDCs) have been clinically validated using the B·R·A·H·M·S PCT™ sensitive Kryptor™ assay. Alternative PCT assays have recently been approved by the Food and Drug Administration for clinical use in the US and require method verification before clinical implementation.

METHODS

Precision, sensitivity, linearity, reportable range, and reference intervals were verified for the Architect B·R·A·H·M·S PCT assay. Accuracy of the Architect B·R·A·H·M·S PCT assay was evaluated by comparison with the B·R·A·H·M·S PCT sensitive Kryptor assay.

RESULTS

The Architect B·R·A·H·M·S PCT assay was found to be precise (CV, ≤4.6%), sensitive (limit of blank, 0.001 ng/mL; limit of quantitation, ≤0.01 ng/mL), and linear according to the manufacturer's claims. The analytical measurement range (0.20-100.00 ng/mL) and the reference interval (≤0.07 ng/mL) were also verified. Patient result comparisons indicated high agreement at 0.10 ng/mL and 0.25 ng/mL and reduced positive agreement at 0.50 ng/mL and 2.00 ng/mL MDCs owing to negative bias compared with the B·R·A·H·M·S PCT sensitive Kryptor assay.

CONCLUSIONS

The Architect B·R·A·H·M·S PCT assay meets most performance specifications claimed by the manufacturer; however, negative bias at 0.50 ng/mL and 2.00 ng/mL PCT concentrations is evident.

A Reflex Protocol for Creatinine Testing Reduces Costs and Maintains Patient Safety

BACKGROUND

The Jaffe and enzymatic methods are the 2 most common methods for creatinine measurement. The Jaffe method is less expensive but subject to interferences. Some laboratory scientists have called for the Jaffe method to be retired.

OBJECTIVE

To determine the most cost-effective and safe protocol for creatinine measurement.

METHOD

We performed a retrospective database review of all outpatient creatinine measurements for 1 year, testing the risk-based reflex testing protocol we had implemented for creatinine measurement. Samples were first measured using the Jaffe method and were reflexed to the enzymatic method if the estimated glomerular filtration rate (eGFR) was between 55 and 65 mL per min per 1.73 m2.

RESULTS

There were 104,530 creatinine measurements, of which 11,420 (10.9%) were reflexed to the enzymatic method. The Jaffe method had a positive bias of 0.08 mg per dL (-6.14 mL/min/1.73 m2 eGFR). A total of 3.4% of the paired reflexed specimens were discordant. Also, 133 (1.2%) of the Jaffe results were classified as false negatives and 3411 (29.9%) were classified as false positives. None of the false-negative results and 5 of the false-positive results were considered clinically significant. Using the reflex protocol saved approximately $40,000 per year.

CONCLUSIONS

The reflex protocol for creatinine measurement can reduce costs with acceptable risk.

Appropriateness of Plasma Transfusion: A College of American Pathologists Q-Probes Study of Guidelines, Waste, and Serious Adverse Events

Context.—

Plasma transfusion guidelines support patient care and safety, management of product wastage, and compliance; yet, there is little information across multiple institutions about use of and adherence to plasma transfusion guidelines.

Objective.—

To survey multiple institutions regarding their plasma transfusion guidelines and compliance, plasma wastage rates, and incidence of transfusion reactions associated with plasma transfusion.

Design.—

The College of American Pathologists Q-Probes model was used to collect data from 89 participating institutions. Each site was asked to provide data relevant to its most recent 40 adult patient plasma transfusion episodes, and complete a questionnaire regarding plasma transfusion guidelines, utilization and wastage of plasma, and transfusion reactions related to plasma transfusion.

Results.—

The participating institutions reported a total of 3383 evaluable plasma transfusion episodes with transfusion of 9060 units of plasma. Compliance with institution-specific guidelines was seen in 3018 events (89%). Pretransfusion and posttransfusion coagulation testing was done in 3281 (97%) and 3043 (90%) of these episodes, respectively. Inappropriate criteria were noted for more than 100 transfusion episodes. Thirty-two plasma transfusion episodes (1%) were associated with a transfusion reaction. Serious and fatal reactions were reported. Median plasma wastage rate for the year preceding the study was 4.5%.

Conclusions.—

Most participating institutions are compliant with plasma transfusion guidelines based on published references, supported by appropriate testing. With transfusions for indications that lack evidence of efficacy and incidence of transfusion reactions, there is an ongoing role for transfusion service leaders to continue to update and monitor plasma transfusion practices.

Process Optimization to Improve Immunosuppressant Drug Testing Turnaround Time

OBJECTIVES

Timely reporting of immunosuppressant (ISP) drug level results is needed for transplant patient management. This study characterized the local ISP testing process, identified bottlenecks and implemented process improvements to meet turnaround time requirements.

METHODS

Laboratory information time stamps, direct observation and discussion with staff were used to construct a value stream map of the ISP testing process to identify process bottlenecks. Improvements were implemented to attain the required turnaround time.

RESULTS

Baseline performance of the existing ISP process (seven weeks, n = 272 samples) indicated that only 28% of samples were reported by 2:00 pm Major bottlenecks were identified to be the analytical run schedule, instrument delays, difficulty identifying ISP samples at intake, and difficulty collecting specimens. Process changes resulted in a median of 76% samples reported by 2:00 pm

CONCLUSIONS

: Adjusting ISP collection and analysis processes improved the laboratory's ability to meet physician requested result reporting time of 2:00 pm.

A Risk Assessment of the Jaffe vs Enzymatic Method for Creatinine Measurement in an Outpatient Population

BACKGROUND

The Jaffe and enzymatic methods are the two most common methods for measuring serum creatinine. The Jaffe method is less expensive than the enzymatic method but is also more susceptible to interferences. Interferences can lead to misdiagnosis but interferences may vary by patient population. The overall risk associated with the Jaffe method depends on the probability of misclassification and the consequences of misclassification. This study assessed the risk associated with the Jaffe method in an outpatient population. We analyzed the discordance rate in the estimated glomerular filtration rate based on serum creatinine measurements obtained by the Jaffe and enzymatic method.

METHODS

Method comparison and risk analysis. Five hundred twenty-nine eGFRs obtained by the Jaffe and enzymatic method were compared at four clinical decision limits. We determined the probability of discordance and the consequence of misclassification at each decision limit to evaluate the overall risk.

RESULTS

We obtained 529 paired observations. Of these, 29 (5.5%) were discordant with respect to one of the decision limits (i.e. 15, 30, 45 or 60 ml/min/1.73m2). The magnitude of the differences (Jaffe result minus enzymatic result) were significant relative to analytical variation in 21 of the 29 (72%) of the discordant results. The magnitude of the differences were not significant relative to biological variation. The risk associated with misclassification was greatest at the 60 ml/min/1.73m2 decision limit because the probability of misclassification and the potential for adverse outcomes were greatest at that decision limit.

CONCLUSION

The Jaffe method is subject to bias due to interfering substances (loss of analytical specificity). The risk of misclassification is greatest at the 60 ml/min/1.73m2 decision limit; however, the risk of misclassification due to bias is much less than the risk of misclassification due to biological variation. The Jaffe method may pose low risk in selected populations if eGFR results near the 60 ml/min/1.73m2 decision limit are interpreted with caution.

Practices for Identifying and Rejecting Hemolyzed Specimens Are Highly Variable in Clinical Laboratories

Context

Hemolysis is an important clinical laboratory quality attribute that influences result reliability.

Objective

To determine hemolysis identification and rejection practices occurring in clinical laboratories.

Design

We used the College of American Pathologists Survey program to distribute a Q-Probes–type questionnaire about hemolysis practices to Chemistry Survey participants.

Results

Of 3495 participants sent the questionnaire, 846 (24%) responded. In 71% of 772 laboratories, the hemolysis rate was less than 3.0%, whereas in 5%, it was 6.0% or greater. A visual scale, an instrument scale, and combination of visual and instrument scales were used to identify hemolysis in 48%, 11%, and 41% of laboratories, respectively. A picture of the hemolysis level was used as an aid to technologists' visual interpretation of hemolysis levels in 40% of laboratories. In 7.0% of laboratories, all hemolyzed specimens were rejected; in 4% of laboratories, no hemolyzed specimens were rejected; and in 88% of laboratories, some specimens were rejected depending on hemolysis levels. Participants used 69 different terms to describe hemolysis scales, with 21 terms used in more than 10 laboratories. Slight and moderate were the terms used most commonly. Of 16 different cutoffs used to reject hemolyzed specimens, moderate was the most common, occurring in 30% of laboratories. For whole blood electrolyte measurements performed in 86 laboratories, 57% did not evaluate the presence of hemolysis, but for those that did, the most common practice in 21 laboratories (24%) was centrifuging and visually determining the presence of hemolysis in all specimens.

Conclusions

Hemolysis practices vary widely. Standard assessment and consistent reporting are the first steps in reducing interlaboratory variability among results.

Clinical Laboratory Quality Practices When Hemolysis Occurs

Context

Hemolyzed specimens delay clinical laboratory results, proliferate unnecessary testing, complicate physician decisions, injure patients indirectly, and increase health care costs.

Objective

To determine quality improvement practices when hemolysis occurs.

Design

We used the College of American Pathologists (CAP) Survey Program to distribute a Q-Probes–type questionnaire about hemolysis practices to CAP Chemistry Survey participants.

Results

Of 3495 participants sent the questionnaire, 846 (24%) responded. Although 85%, 69%, and 55% of participants had written hemolysis policies for potassium, lactate dehydrogenase, and glucose, respectively, only a few (46%, 40%, and 40%) had standardized hemolysis reports between their primary and secondary chemistry analyzers for these 3 analytes. Most participants (70%) had not attempted to validate the manufacturers' hemolysis data for these 3 analytes; however, essentially all who tried, succeeded. Forty-nine percent of participants had taken corrective action to reduce hemolysis during the past year and used, on average, 2.4 different actions, with collection and distribution of hemolysis data to administrative leadership (57%), troubleshooting outliers (55%), retraining phlebotomist (53%), and establishment of quality improvement teams among the laboratory and at problem locations (37%) being the most common actions. When asked to assess their progress in reducing hemolysis, 70% noted slow to no progress, and 2% gave up on improvement. Upon measuring potassium, lactate dehydrogenase, and glucose, approximately 60% of participants used the same specimen flag for hemolysis as for lipemia and icterus.

Conclusions

Hemolysis decreases the quality and increases the cost of health care. Practices for measuring, reporting, and decreasing hemolysis rates need improvement.

A mathematical procedure to estimate the impact of a change in method on discordance or misclassification at a decision limit in laboratory method comparison studies

BACKGROUND

Laboratories often adopt new methods. It would be useful to have a statistical procedure to estimate the incremental impact of a change in assay.

METHODS

Mathematical modeling, statistical analysis, and case example.

RESULTS

We derived equations to estimate the proportion of discordant results that can be attributed to the new laboratory method. The calculations were demonstrated by comparing eGFR values based on creatinine values determined using the enzymatic method (existing method) and Jaffe method (new method). The discordance rate at the 60 ml/min eGFR decision limit was 3.15%. In this example, we estimated that 60% of the discordant results could be attributed to the Jaffe method.

CONCLUSION

The sources of discordance in a laboratory method comparison study can be divided into three categories: The baseline discordance due to imprecision in the established method, the incremental discordance due to imprecision in the new method, and lack of analytical specificity. Discordance due to imprecision can be attributed to each individual method. Discordance due to bias can be attributed to individual methods if information is available to estimate the rate of biased observations in either method. Such information can be used to estimate the incremental cost effectiveness associated with the adoption of a new method.

Utility of repeat testing of critical values: a Q-probes analysis of 86 clinical laboratories

CONTEXT

A common laboratory practice is to repeat critical values before reporting the test results to the clinical care provider. This may be an unnecessary step that delays the reporting of critical test results without adding value to the accuracy of the test result.

OBJECTIVES

To determine the proportions of repeated chemistry and hematology critical values that differ significantly from the original value as defined by the participating laboratory, to determine the threshold differences defined by the laboratory as clinically significant, and to determine the additional time required to analyze the repeat test.

DESIGN

Participants prospectively reviewed critical test results for 4 laboratory tests: glucose, potassium, white blood cell count, and platelet count. Participants reported the following information: initial and repeated test result; time initial and repeat results were first known to laboratory staff; critical result notification time; if the repeat result was still a critical result; if the repeat result was significantly different from the initial result, as judged by the laboratory professional or policy; significant difference threshold, as defined by the laboratory; the make and model of the instrument used for primary and repeat testing.

RESULTS

Routine, repeat analysis of critical values is a common practice. Most laboratories did not formally define a significant difference between repeat results. Repeated results were rarely considered significantly different. Median repeated times were at least 17 to 21 minutes for 10% of laboratories. Twenty percent of laboratories reported at least 1 incident in the last calendar year of delayed result reporting that clinicians indicated had adversely affected patient care.

CONCLUSION

Routine repeat analysis of automated chemistry and hematology critical values is unlikely to be clinically useful and may adversely affect patient care.

Clinical Consequences of Specimen Rejection: A College of American Pathologists Q-Probes Analysis of 78 Clinical Laboratories

Context.—Clinical laboratory specimens may be rejected as unsuitable for analysis for a variety of reasons and specimen rejection may have significant clinical consequences.

Objective.—To quantify the clinical consequences of specimen rejection and determine the impact of laboratories' policies and practices on these consequences.

Design.—Participants prospectively reviewed consecutive blood and urine specimens submitted to the chemistry and/or hematology laboratories to identify rejected specimens. For each rejected specimen, the patient's age, specimen type, testing priority, rejection reason, time from specimen receipt to receipt of recollected/relabeled specimen, recollection method, and test result time were recorded. Specimen/test abandonment was determined by failure to recollect or relabel a rejected specimen. Each laboratory's policy regarding relabeling of incorrectly labeled specimens was recorded, along with how many relabeled specimens were subsequently discovered to be mislabeled.

Results.—Specimen rejection led to a (1) high rate of specimen recollection, (2) delay in result availability (median of 65 minutes), and (3) high rate of specimen/test abandonment. Longer test result delay was associated with higher hospital bed size; and higher test abandonment rate, with failure of the laboratory to request specimen recollection. Relabeling of incorrectly labeled specimens was found to be of little benefit and was associated with a substantial percentage of subsequently mislabeled specimens.

Conclusion.—Specimen rejection has significant clinical consequences, including patient discomfort, significant delay in result availability, and high rate of specimen/test abandonment. Allowing routine relabeling of incorrectly labeled specimens is a dangerous practice, with little measureable benefit and with an increased risk to patient safety.

Utilization of Stat Test Priority in the Clinical Laboratory: A College of American Pathologists Q-Probes Study of 52 Institutions

Context.—Utilization of stat testing priority is a balance between safe, efficient patient management and resource expenditure.

Objective.—To determine the rate of stat testing, compare rates among institutions, and determine the distribution of turnaround time expectations for different turnaround time priorities.

Design.—During a 7-day period, participants prospectively determined the total number of chemistry, hematology, and coagulation billable tests from inpatients and emergency department patients. Among these, the total numbers of billable tests performed stat were identified. Laboratories also reported the levels of test priority they offered and turnaround expectations for each level of test priority.

Results.—Fifty institutions submitted data for the study, with 2 additional participants submitting partial results. Participants identified 639 589 chemistry, hematology, and coagulation billable tests, with 229 896 (35.9%) performed stat. The stat rate varied from 21.3% at the 10th percentile to 55.4% at the 90th percentile, with a median of 37.0% of participants' tests performed stat. Laboratories include a mean of 206 tests in chemistry, hematology, and coagulation test menus, with 67% of these tests offered stat. The fraction of the test menu offered stat varied from 29.0% at the 10th percentile to 97.8% at the 90th percentile, with a median of 73.3% of tests on the menu offered stat. The most common number of testing priorities offered by participating laboratories was 3 (44.2%).

Conclusions.—Among the 52 participating laboratories, the median stat testing rate was 37.0% and a median 73.3% of the test menu was offered stat.

Method comparison of the Ortho Vitros Fusion 5,1 chemistry analyzer and the Roche COBAS Integra 400 for urine drug screen testing in the emergency department

Exposure to drugs and toxins is a major cause for the rising number of emergency department visits each year. Immunoassays are commonly used in the emergency department to provide rapid turnaround time for acute care. The purpose of this study was to compare two automated immunoassay chemistry analyzers to determine which platform produced the fewest number of false positive/negative results. Residual patient urine samples were were collected for each of the following drugs/drug classes: cocaine (n = 40), opiates (n = 45), and amphetamines (n = 54) and confirmed either positive or negative by mass spectrometry. Split sample analyses of these specimens were performed on both the Roche COBAS INTEGRA 400 plus and Ortho Vitros 5,1 FS instruments. The results from the two chemistry analyzers were compared to confirmed results. Both immunoassays were prone to false positive results for cocaine and false negative results for opiates and amphetamines. The Vitros Fusion analyzer generated fewer false positive and false negative results for opiate and amphetamine testing than the Roche Integra, but the platforms performed comparably for cocaine.

Should the qualitative serum pregnancy test be considered obsolete?

Qualitative and quantitative serum human chorionic gonadotropin (hCG) tests are used to diagnose pregnancy. We assessed physicians' perceptions and compared turnaround times (TATs) and performance characteristics of both tests. We surveyed 1,058 physicians about their perceptions of hCG tests. Seven months of TAT data were analyzed. hCG was measured in all qualitative samples. Pregnancy status was determined by chart review. Of the physicians surveyed, 183 responded. Forty-nine percent preferred qualitative over quantitative serum tests for determining pregnancy status. Physicians were willing to wait 45 minutes for results from either test. Qualitative tests are performed faster than quantitative tests, but TATs were not significantly different when sample transport time was considered. The negative predictive value of both tests was 99.9%. Qualitative serum hCG testing could be replaced by quantitative hCG tests, but there is no clear advantage to doing so.

Managing transfusion service quality

CONTEXT

Providing blood products for transfusions is a complex process subject to errors both within and outside the transfusion service. Transfusion-related errors can have grave consequences for the patient undergoing transfusion. As with many processes performed within health care systems, there is an expectation of error-free practice. Although this is an unobtainable goal, a focused quality-management plan, employing a medical event reporting system in a just working environment, can effect measurable system-quality improvement.

OBJECTIVE

To illustrate the intrinsic value of quality-improvement activities through discussion of examples of quality misadventures from our transfusion service during the past 20 years.

DATA SOURCES

Examples of quality-improvement activities were extracted from our quality-system archives. The published literature on transfusion quality was reviewed.

CONCLUSIONS

Active reporting, structured investigation, and systematic resolution of transfusion-related errors are effective methods for improving and maintaining transfusion quality.

Blood bank safety practices: mislabeled samples and wrong blood in tube--a Q-Probes analysis of 122 clinical laboratories

CONTEXT

Although a rare occurrence, ABO incompatible transfusions can cause patient morbidity and mortality. Up to 20% of all mistransfusions are traced to patient misidentification and/or sample mislabeling errors that occur before a sample arrives in the laboratory. Laboratories play a significant role in preventing mistransfusion by identifying wrong blood in tube and rejecting mislabeled samples.

OBJECTIVES

To determine the rates of mislabeled samples and wrong blood in tube for samples submitted for ABO typing and to survey patient identification and sample labeling practices and sample acceptance policies for ABO typing samples across a variety of US institutions.

DESIGN

One hundred twenty-two institutions prospectively reviewed inpatient and outpatient samples submitted for ABO typing for 30 days. Labeling error rates were calculated for each participant and tested for associations with institutional demographic and practice variable information. Wrong-blood-in-tube rates were calculated for the 30-day period and for a retrospective 12-month period. A concurrent survey collected institution-specific sample labeling requirements and institutional policies regarding the fate of mislabeled samples.

RESULTS

For all institutions combined, the aggregate mislabeled sample rate was 1.12%. The annual and 30-day wrong-blood-in-tube aggregate rates were both 0.04%. Patient first name, last name, and unique identification number were required on the sample by more than 90% of participating institutions; however, other requirements varied more widely.

CONCLUSIONS

The rates of mislabeled samples and wrong blood in tube for US participants in this study were comparable to those reported for most European countries. The survey of patient identification and sample labeling practices and sample acceptance policies for ABO typing samples revealed both practice uniformity and variability as well as significant opportunity for improvement.

Comparative performance of three anti-factor Xa heparin assays in patients in a medical intensive care unit receiving intravenous, unfractionated heparin

The availability of automated anti-Xa heparin assays provides the opportunity to manage patient unfractionated heparin levels directly, rather than by the activated partial thromboplastin time. Because critically ill patients can acquire an antithrombin deficiency, we compared the performance of 3 anti-Xa heparin assays, 1 with and 2 without antithrombin supplementation, by analyzing in vitro aliquots of plasma with defined antithrombin levels and specimens from intensive care patients receiving intravenous heparin therapy. Heparin concentration recovery, in vitro, was dependent on the plasma antithrombin concentration for all 3 assays. The antithrombin-supplemented assay demonstrated improved heparin recovery in direct correlation to the heparin concentration in the plasma. The greatest effect of antithrombin supplementation occurred when the antithrombin level dropped below 40%, a level present in only 5% of the patient specimens. Analysis of patient specimens demonstrated significant correlation among the 3 assays. Classification of the clinical adequacy of patient heparin levels showed agreement of 80% or more between the antithrombin-supplemented and nonsupplemented assays. The antithrombin-supplemented assay did not significantly improve clinical usefulness.

Analytic validation and clinical evaluation of the STA LIATEST immunoturbidimetric D-dimer assay for the diagnosis of disseminated intravascular coagulation

To evaluate the diagnostic performance of a quantitative, immunoturbidimetric D-dimer assay and compare it with other components of the proposed International Society on Thrombosis and Haemostasis disseminated intravascular coagulation (DIC) diagnostic algorithm, we retrospectively analyzed the D-dimer, platelet count, prothrombin time, and fibrinogen results for all eligible hospitalized patients (n = 241) who had a D-dimer assay ordered during a 12-month period. A receiver operating characteristic (ROC) curve constructed from the maximum D-dimer measurement for all patients was significant (P < .001) with an area under the curve (AUC) of 0.94. The ROC curves of the other tests were each significant (P < .001), but the AUCs of the prothrombin time (0.74), fibrinogen level (0.70), and platelet count (0.67) did not approach that of the D-dimer. A D-dimer cutoff of 8.2 microg/mL (8,200 microg/L) optimized sensitivity and negative predictive value for the total population and patients with a predisposing condition. Validation against 286 additional patients in a separate analysis verified the diagnostic performance of the aforementioned cutoff. A sensitive, immunoturbidimetric D-dimer assay, by itself provides excellent sensitivity and negative predictive value for the diagnosis of DIC.

False-positive AxSYM cardiac troponin I results in a 53-year-old woman

A number of classes of endogenous antibodies, including heterophile, rheumatoid factor, and autoantibodies, can interfere with immunoassay measurements of many different analytes. Heterophile and rheumatoid factor antibody interferences have been described previously for the AxSYM cardiac troponin I assay. Several commercial products have been developed to neutralize heterophile antibody interferences. We describe a patient with multiple apparently falsely elevated cardiac troponin I results that were unique to the AxSYM analyzer. These cardiac troponin I results diluted linearly. When treated with 2 different heterophile-blocking reagents, the magnitudes of the falsely elevated results increased 17- and 26-fold, and these results also demonstrated dilution linearity. This interfering substance could be removed by passage through an immobilized protein A column and by polyethylene glycol precipitation. It does not appear to be a classic heterophile antibody, nor is it a paraprotein. Laboratorians must remain constantly vigilant for immunoassay interferences that lead to clinically significant inaccurate results and must recognize that accepted methods for detecting and neutralizing the interference may be ineffective.

Discontinuation of the bleeding time test without detectable adverse clinical impact

BACKGROUND

The bleeding time (BT) test predicts a higher bleeding complication rate in populations at risk for inherited or acquired platelet dysfunction, but it is of limited assistance in evaluating individual patients. There are no reports of clinical outcomes after discontinuation of the BT test.

METHODS

Interviews with a subset of the physicians who had ordered the BT test before discontinuation of the test were conducted. The total number of platelet-aggregation tests, the mean number of monthly, unmodified platelet units transfused, the incidence of kidney biopsy complications, and the number of doses of 1-deamino-8-D-arginine vasopressin (DDAVP) administered 5 months before and after discontinuation of the BT test were compared. We recorded the rates of bleeding complications in the Major Surgery Risk Pool during the 12 months before and the 5 months after the discontinuation of the BT test.

RESULTS

Clinicians reported they did not significantly change their preprocedural work-ups, postpone an invasive procedure, experience an increase in bleeding complications, or increase their use of blood products after discontinuation of the BT test. Platelet-aggregation tests (n = 9, before and after), platelet transfusions (P = 0.958), and DDAVP administration (before = 24; after = 10) did not increase after discontinuation of the BT test. The rate of postprocedural bleeding complications did not increase significantly in either Major Surgery Risk Pool cases (<3final sigma deviation from the mean rate) or in patients undergoing renal biopsies (P = 0.225 for decrease in hematocrit; P = 1.000 for the percentage of patients transfused) after discontinuation of the BT test.

CONCLUSIONS

Our study failed to identify a clinically significant, negative impact of discontinuing the BT test.

Discontinuation of the Bleeding Time Test without Detectable Adverse Clinical Impact

Background: The bleeding time (BT) test predicts a higher bleeding complication rate in populations at risk for inherited or acquired platelet dysfunction, but it is of limited assistance in evaluating individual patients. There are no reports of clinical outcomes after discontinuation of the BT test.

Methods: Interviews with a subset of the physicians who had ordered the BT test before discontinuation of the test were conducted. The total number of platelet-aggregation tests, the mean number of monthly, unmodified platelet units transfused, the incidence of kidney biopsy complications, and the number of doses of 1-deamino-8-d-arginine vasopressin (DDAVP) administered 5 months before and after discontinuation of the BT test were compared. We recorded the rates of bleeding complications in the Major Surgery Risk Pool during the 12 months before and the 5 months after the discontinuation of the BT test.

Results: Clinicians reported they did not significantly change their preprocedural work-ups, postpone an invasive procedure, experience an increase in bleeding complications, or increase their use of blood products after discontinuation of the BT test. Platelet-aggregation tests (n = 9, before and after), platelet transfusions (P = 0.958), and DDAVP administration (before = 24; after = 10) did not increase after discontinuation of the BT test. The rate of postprocedural bleeding complications did not increase significantly in either Major Surgery Risk Pool cases (&lt;3ς deviation from the mean rate) or in patients undergoing renal biopsies (P = 0.225 for decrease in hematocrit; P = 1.000 for the percentage of patients transfused) after discontinuation of the BT test.

Conclusions: Our study failed to identify a clinically significant, negative impact of discontinuing the BT test.

Overestimation of hemoglobin in a patient with an IgA-kappa monoclonal gammopathy

A patient with multiple myeloma had an automated blood count performed on a Coulter STK-S counter that repeatedly failed internal limits for both mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration. The calculated hematocrit agreed with a spun hematocrit, suggesting that the hemoglobin concentration was being overestimated by the automated counter. Measurement of the plasma hemoglobin concentration of the sample, which showed no visible hemolysis, gave a hemoglobin concentration of 32 g/L on the STK-S analyzer. Correction of the whole blood hemoglobin using the plasma hemoglobin gave a value consistent with the hematocrit. The corrected mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration values were within standard limits. This patient's paraprotein was characterized as IgA-kappa and was present at a concentration of 61 g/L. The hemoglobin concentration measured on whole blood by Sysmex NE 8000 and Technicon H*1E autoanalyzers agreed reasonably well with the corrected result from the STK-S.

Detection of a common mutation in factor V gene responsible for resistance to activate protein C causing predisposition to thrombosis

Hereditary predisposition to thrombosis due to activated protein C resistance (APCR) has been attributed to a missense mutation in the factor V gene at nucleotide 1691 (G to A), causing replacement of arginine at codon 506 with glutamine. Using an RFLP-PCR assay to detect this mutation, we measured a prevalence of 3.3% in healthy Caucasians and 1.25% in healthy African-Americans. In addition, we evaluated a total of 90 consecutive specimens submitted to the coagulation laboratory at the Medical College of Virginia for the presence of this mutation. We compared our results for 78 of these specimens with the values measured by a modified partial thromboplastin assay, the COATEST. Twelve of the 90 samples could not be tested using the COATEST because the patients were undergoing anticoagulant therapy. One of the latter 12 specimens was positive by the RFLP-PCR test. Using the genetic test as the definitive assay and the cutoff value established for distinguishing between normal and abnormal results by the COATEST, the COATEST had a sensitivity of 50% and specificity of 93% for the detection of factor V mutation. Analysis of the 90 samples stratified by ethnic groups revealed a frequency of mutation of 13.3% for Caucasians and 6.88% for African-Americans, although with the present sample size, the difference was not statistically significant. Although the COATEST is technically simpler to perform than the genetic test for diagnosing the presence of the factor V mutation, its use for this purpose is limited due to low sensitivity. Thus where this disorder is clinically suspected, submission of the specimen directly for genetic testing by RFLP-PCR or equivalent assay should be considered.

Red cells and platelets. Modifications for special patients

Blood components are modified to meet the clinical requirements of specific patient populations. The clinical indications for some well-established components have narrowed with the development of new technology. Leukoreduced blood components are being considered for a variety of clinical applications. Published data support the use of leukoreduced components to prevent febrile nonhemolytic transfusion reactions. The routine use of such components for other indications should be considered experimental, and the cost effectiveness of experimentally validated indications should be evaluated.

Comparison of PCR with southern hybridization for the routine detection of immunoglobulin heavy chain gene rearrangements

The development of a reliable polymerase chain reaction (PCR) technique for the routine detection of clonal immunoglobulin heavy chain (IgH) gene rearrangements would represent an attractive alternative to Southern hybridization analysis because of the relative simplicity of PCR protocols, and because the requirements for both quality and quantity of DNA would be considerably less stringent. To assess the utility of PCR for the routine detection of clonal IgH gene rearrangements, samples from 123 adult patients were evaluated and analysis by PCR amplification using IgH Framework 1 or Framework 3 variable region consensus primers was compared with analysis by restriction endonuclease digestion and Southern hybridization with genomic, IgH probes. The authors found that 90% of IgH genes found to be rearranged by Southern hybridization are detected by the PCR technique. An additional 9 patient samples had clonal IgH gene rearrangements that were detectable by PCR alone. Eight of these nine patients had a history of a clonal hematopoietic process at either the morphologic or molecular level, and six had a history of a B-cell malignancy. It is likely that these specimens contained clonal lymphoid populations undetected by the Southern hybridization technique. Thus, the diagnostic sensitivity and specificity of the PCR method for the detection of B-cell tumors were 91% and 95%, respectively. The combination of improved analytical sensitivity and specimen flexibility of the IgH PCR assay could make it the method of choice for the routine detection of clonal IgH gene rearrangements, if minor improvements in the diagnostic sensitivity of the assay can be achieved.

Changes in homing receptor expression on murine lymphokine-activated killer cells during IL-2 exposure

The effects of IL-2 on the expression of homing receptors by lymphocytes of NK or lymphokine activated killer (LAK) cell derivation has not yet been evaluated. We developed a murine model to evaluate the potential of LAK cells to localize into peripheral lymph nodes since LAK cells are used to treat human cancers which have metastasized to these tissues. Using a frozen section binding assay, LAK cell adhesion to the lymph node microvasculature was easily demonstrable. Inhibition studies demonstrated that LAK cell binding to lymph nodes was mediated by mechanisms previously described in T cells. LAK cell surface expression of the 85- to 95-kDa homing receptor recognized by the antibody MEL-14 on LAK cells was assessed by indirect immunofluorescence. The percentage of cells which bound MEL-14 decreased slightly over 3 days of IL-2 exposure (from 73 to 60%), particularly in the large granular lymphocyte (cytotoxic effector) subpopulation (45% MEL-14+). The expression of another homing-related molecule, leukocyte function-associated Ag-1, markedly increased during activation of LAK cells. Despite the expression of these homing receptors, we observed almost no LAK cell localization into lymph nodes in vivo. Furthermore, IL-2 pretreatment of recipient animals did not increase the adhesion of LAK cells to lymph node microvasculature or enhance their extravasation. IL-2 activation of non-T, non-B lymphocytes results in significant changes in both the expression and function of cell surface homing receptors. Our results indicate that in vitro analysis does not always predict in vivo localization potential.

Changes in homing receptor expression on murine lymphokine-activated killer cells during IL-2 exposure

The effects of IL-2 on the expression of homing receptors by lymphocytes of NK or lymphokine activated killer (LAK) cell derivation has not yet been evaluated. We developed a murine model to evaluate the potential of LAK cells to localize into peripheral lymph nodes since LAK cells are used to treat human cancers which have metastasized to these tissues. Using a frozen section binding assay, LAK cell adhesion to the lymph node microvasculature was easily demonstrable. Inhibition studies demonstrated that LAK cell binding to lymph nodes was mediated by mechanisms previously described in T cells. LAK cell surface expression of the 85- to 95-kDa homing receptor recognized by the antibody MEL-14 on LAK cells was assessed by indirect immunofluorescence. The percentage of cells which bound MEL-14 decreased slightly over 3 days of IL-2 exposure (from 73 to 60%), particularly in the large granular lymphocyte (cytotoxic effector) subpopulation (45% MEL-14+). The expression of another homing-related molecule, leukocyte function-associated Ag-1, markedly increased during activation of LAK cells. Despite the expression of these homing receptors, we observed almost no LAK cell localization into lymph nodes in vivo. Furthermore, IL-2 pretreatment of recipient animals did not increase the adhesion of LAK cells to lymph node microvasculature or enhance their extravasation. IL-2 activation of non-T, non-B lymphocytes results in significant changes in both the expression and function of cell surface homing receptors. Our results indicate that in vitro analysis does not always predict in vivo localization potential.

The physiological state as a modifier of radiation-induced cytotoxicity in heterogeneous murine tumor cells growing in vitro

The oxic radiation response (cytotoxicity) of two heterogeneous murine tumor-cell lines cultured in vitro was studied as a function of the cell's physiological state at the time of X-irradiation. The proliferating (P) 66 and 67 cells displayed equal radiosensitivities; however, the quiescent (Q) cells were considerably more radiosensitive than the P cells, and the 66Q cells were even more radiosensitive than the 67Q cells. Also, the 66Q cells continued to proliferate slowly with about 85 per cent in the G1 phase and 10 per cent in the S phase, while the 67 Q cells displayed a more complete G1 arrest (92-95 per cent). A detailed analysis of the metabolic status vs cell-cycle age (i.e. G1 vs S phase) indicated that the cell-cycle age was the predominant factor influencing radiation-induced cytotoxicity in 67 cells. The data also showed that in the plateau phase Q-cell cultures, pH and cell contact were not influencing factors and that the increased radiosensitivity of the Q cells could not be explained on the basis of energy deprivation. Moreover, the 66Q, but not the 67Q cells displayed an increased sensitivity in addition to that caused by the predominant cell-cycle age shift. This extra increase in radiosensitivity is of unknown metabolic origin, but could be related to cellular membrane fragility in the stressed 66Q cells since this extra component of Q-cell radiosensitivity was reduced both by refeeding (metabolic activation) 4 h before X-irradiation and by delayed plating while incubating the cells in Q medium at 37 degrees C after X-irradiation.

Toxic effects of acute glutathione depletion by buthionine sulfoximine and dimethylfumarate on murine mammary carcinoma cells

Glutathione (GSH) depletion to approximately equal to 5% of control for 48 h or longer by 0.05 mM L-buthionine sulfoximine (BSO) led to appreciable toxicity for the 66 murine mammary carcinoma cells growing in vitro [L.A. Dethlefsen et al., Int. J. Radiat. Oncol. Biol. Phys. 12, 1157-1160 (1986)]. Such toxicity in normal, proliferating cells in vivo would be undesirable. Thus the toxic effects after acute GSH depletion to approximately equal to 5% of control by BSO plus dimethylfumarate (DMF) were evaluated in these same 66 cells to determine if this anti-proliferative effect could be minimized. Two hours of 0.025 mM DMF reduced GSH to 45% of control, while 6 h of 0.05 mM BSO reduced it to 16%. However, BSO (6 h) plus DMF (2 h) and BSO (24 h) plus DMF (2 h) reduced GSH to 4 and 2%, respectively. The incorporation (15-min pulses) of radioactive precursors into protein and RNA were unaffected by these treatment protocols. In contrast, cell growth was only modestly affected, but the incorporation of [3H]thymidine into DNA was reduced to 64% of control by the BSO (24 h) plus DMF (2 h) protocol even though it was unaffected by the BSO (6 h) plus DMF (2 h) treatment. The cellular plating efficiencies from both protocols were reduced to approximately equal to 75% of control cells. However, the aerobic radiation response, as measured by cell survival, was not modified at doses of either 4.0 or 8.0 Gy. The growth rates of treated cultures, after drug removal, quickly returned to control rates and the resynthesis of GSH in cells from both protocols was also rapid. The GSH levels after either protocol were slightly above control by 12 h after drug removal, dramatically over control (approximately equal to 200%) by 24 h, and back to normal by 48 h. Thus even a relatively short treatment with BSO and DMF resulting in a GSH depletion to 2-5% of control had a marked effect on DNA synthesis and plating efficiency and a modest effect on cellular growth. One cannot rule out a direct effect of the drugs, but presumably the antiproliferative effects are due to a depletion of nuclear GSH with the subsequent inhibition of the GSH/glutaredoxin-mediated conversion of ribonucleotides to deoxyribonucleotides. However, even after extended treatment, upon drug removal, GSH was rapidly resynthesized and cellular DNA synthesis and growth quickly resumed.

Delayed enhanced effects of Adriamycin on the X-irradiation-induced gastrointestinal toxicity in mice

The delayed responses of C3H mice which had been pretreated with various single-dose and two-dose fractionated Adriamycin/X-irradiation protocols were evaluated by stressing the 120-day survivors with either whole-abdomen X-irradiation (LD50/7 assay) or whole-body X-irradiation (crypt colony survival). Pretreatment with Adriamycin alone was as toxic as Adriamycin plus X-irradiation for the animals stressed at 120 days (LD50/7 assay). There was no induced cellular radioresistance (D0) and no apparent increase in crypt size as indicated indirectly by the 10-clone dose at 120 days after completion of treatment. The increased lethality of the X-irradiation-stressed 120-day survivors was most likely a primary gastrointestinal response with little or no contribution from either bone marrow or kidney toxicity. The effect was apparently due to a persistent Adriamycin-induced antiproliferative response at the cellular level but the molecular mechanisms are unknown. Such data suggest caution to our clinical colleagues. Cancer patients treated with high doses of Adriamycin, independent of concomitant X-irradiation, will most likely be moderately to severely compromised in their ability to respond to a stress which requires cellular proliferation, and, based on the murine data, this effect is persistent if, indeed, not permanent.

In vivo cytotoxicity of misonidazole and hyperthermia in a transplanted mouse mammary tumor

The cytotoxicity of misonidazole (miso) in vivo in unclamped tumors at hyperthermic temperatures, and in clamped tumors at hypothermic, euthermic, and hyperthermic temperatures has been examined. No cytotoxicity, measured as increased tumor control, was observed in unclamped tumors heated 30 min after systemic miso administration. This may reflect the short serum half-time of miso in the mouse and a small hypoxic fraction in this tumor system. There was, however, significant miso cytotoxicity in clamped tumors at euthermic and hyperthermic temperatures when the clamp was applied 30 min after systemic miso. The degree of cytotoxicity observed was dependent upon the temperature of incubation, the length of clamping, and the dose of miso.

Change in the in vivo hyperthermic response resulting from the metabolic effects of temporary vascular occlusion

Previous workers have reported that clamping of animal tumors in vivo enhanced the effect of hyperthermia; the enhancement has been attributed to pH and nutritional effects of vascular occlusion. It has not been clear, however, the degree to which improved heating patterns or effects on the tumor cells and vasculature from the clamping procedure itself might have contributed to the observed effect. In the experiments herein reported, care was taken to insure comparable heating of C3H mouse mammary tumors transplanted on the flank whether clamped or unclamped. Clamping for one hour with hyperthermia during the final 30 minutes caused a marked thermosensitization as measured by tumor control. The temperature at 30 minutes heating to control 50% of the tumors for 120 days (TCT 50-120) was reduced from 46.8 degrees C in controls to 43.5 degrees C in clamped tumors, a difference of 3.3 +/- 0.09 degrees C. No cytotoxicity from the clamping alone was evident by assessment of subsequent tumor growth and no lasting vascular effects could be detected by 133Xe washout and tumor growth. Since the techniques used produced essentially identical heating patterns, we conclude that the striking enhancement in hyperthermic response in clamped tumors can be attributed to the metabolic consequences of temporary vascular occlusion.