Higher risk of kidney graft failure in the presence of anti-angiotensin II type-1 receptor antibodies.

Reports have associated non-HLA antibodies, specifically those against angiotensin II type-1 receptor (AT1R), with antibody-mediated kidney graft rejection. However, association of anti-AT1R with graft failure had not been demonstrated. We tested anti-AT1R and donor-specific HLA antibodies (DSA) in pre- and posttransplant sera from 351 consecutive kidney recipients: 134 with biopsy-proven rejection and/or lesions (abnormal biopsy group [ABG]) and 217 control group (CG) patients. The ABG's rate of anti-AT1R was significantly higher than the CG's (18% vs. 6%, p < 0.001). Moreover, 79% of ABG patients with anti-AT1R lost their grafts (vs. 0%, CG), anti-AT1R levels in 58% of those failed grafts increasing posttransplant. With anti-AT1R detectable before DSA, time to graft failure was 31 months-but 63 months with DSA detectable before anti-AT1R. Patients with both anti-AT1R and DSA had lower graft survival than those with DSA alone (log-rank p = 0.007). Multivariate analysis showed that de novo anti-AT1R was an independent predictor of graft failure in the ABG, alone (HR: 6.6), and in the entire population (HR: 5.4). In conclusion, this study found significant association of anti-AT1R with graft failure. Further study is needed to establish causality between anti-AT1R and graft failure and, thus, the importance of routine anti-AT1R monitoring and therapeutic targeting.

Extremely high association between appearance of HLA antibodies and failure of kidney grafts in a five-year longitudinal study.

Longitudinal studies were conducted over a five-year period for HLA antibodies on 493 sera tested from 54 kidney transplant patients. HLA single antigen beads were employed to establish donor specificity of the antibodies. Only 3 of 22 patients without antibodies rejected a graft in contrast to 17 out of 32 patients with posttransplant antibodies (p = 0.003). Using a serum creatinine value of 4.0 mg/dL as the cut-off for a failed graft, 4 of 22 patients without antibodies failed compared to 21 of 32 with antibodies (p = 0.0006). Among patients with donor-specific antibodies (DSA) 13 of 15 failed (p = 0.000004). Even among patients with non-donor specific antibodies (NDSA), 8 of 17 failed (p = 0.05). Among patients who could be identified as making de novo antibodies (since they developed antibodies while not having antibodies for more than six months after transplantation), 6 of 11 failed (p = 0.03). Sequential testing for HLA antibodies shows that antibodies appear prior to a rise in serum creatinine and subsequent graft failure. The very strong association between the production of HLA antibodies after transplantation and graft failure indicates the importance of monitoring for posttransplant HLA antibodies.

Effect of reduction in ciprofloxacin use on prevalence of meticillin-resistant Staphylococcus aureus rates within individual units of a tertiary care hospital.

Previous studies have shown a correlation between fluoroquinolone use in hospitals and rates of meticillin-resistant Staphylococcus aureus (MRSA) infection. This study examined the effect on MRSA infection rates within individual adult units of a tertiary care teaching hospital after instituting a programme to decrease ciprofloxacin use. Clinical specimens positive for S. aureus were determined on all adult inpatient units between 1 January 2004 and 31 December 2005. Units with >10 isolates of S. aureus per year were included in the analysis. Ciprofloxacin use, measured in defined daily doses per 1000 patient-days, was determined for each unit during the same time period. Ciprofloxacin use and MRSA rates for 2004 and 2005 were compared. In the 17 units studied, ciprofloxacin use decreased by 31.2% (P<0.0001). The MRSA rate in these units decreased from 59.6% to 54.2% (P=0.122). There was a correlation between ciprofloxacin use and the MRSA rate within these units (r=0.70; 95% confidence interval -0.01-0.94; P=0.053). Within individual units, there was a variable response. In seven of the units, there was an increase in the MRSA rate despite a reduction in ciprofloxacin use, suggesting that other factors (length of stay, infection control and community-acquired MRSA) may have contributed. Although many factors are associated with high MRSA rates, ciprofloxacin use appears to be a contributing factor. Reducing the use of ciprofloxacin may be a means of controlling MRSA in the hospital setting.

Transient nature of interference effects from heterophile antibodies: examples of interference with cardiac marker measurements.

Two-site immunoassay methods have become the standard technique for measurement of a wide variety of drugs, hormones, and cell proteins. One limitation of these methods is their susceptibility to interference from heterophilic antibodies present in the sera of some patients. Human anti-murine antibodies represent a common heterophile antibody that can bind to mouse immunoglobulin and as well as to immunoglobulin from other species. While the mechanism of human anti-murine antibody interference has been well characterized, the time course over which this interference occurs and the susceptibility of different immunoassay procedures to human anti-murine antibody interference from patients with human anti-murine antibody have not been as well described. We report on the time course of interference in assays for cardiac markers for two patients with human anti-murine antibodies. We measured creatine kinase MB isoenzyme (CKMB) and troponins I and T using three different vendors' immunoassay procedures. Our results demonstrate that assay interference due to human anti-murine antibody interference is a transient phenomenon. In one of our patients, human anti-murine antibody interference appeared suddenly, peaked approximately 9 days following its appearance, and gradually resolved over the next 3 weeks. In addition, we found that immunoassay methods from different vendors can show highly variable interference effects when human anti-murine antibody-containing specimens are analyzed.

Multiple regression analysis of interference effects from a hemoglobin-based oxygen carrier solution.

The use of hemoglobin-based oxygen carrier solutions in patients requiring blood transfusion will necessitate that clinical laboratories have mechanisms in place to evaluate the potential interference effect of these substances on testing methods. Because these oxygen carrier solutions contain acellular hemoglobin, but do not contain many of the intracellular enzymes and ions present in erythrocytes, interference effects from blood substitutes may be quite different when compared to in vivo or in vitro lysis of erythrocytes. We evaluated the potential interference effect of Diaspirin Cross-linked Hemoglobin on 29 different clinical laboratory analytes. Various combinations of these analytes were tested using the Hitachi 747 and 911 systems, a Beckman CX3, an Abbott AxSym, a Bayer Immuno I, and a Dade ACA IV; a total of 60 analyte/instrument combinations. We used the method of multiple regression analysis to classify interferences as analyte-dependent, analyte-independent, or a combination of the first two types. The presence of clinically significant test interference was derived by using the criteria for maximum allowable error specified in the Clinical Laboratory Improvement Amendments of 1988. Using these criteria, we found significant interference from Diaspirin Cross-linked Hemoglobin with 13 of 29 analytes tested. Interference was noted with the Hitachi 747 and 911 methods for albumin, alkaline phosphatase, total and conjugated bilirubin, cholesterol, total carbon dioxide, iron, lactate dehydrogenase, magnesium, total protein, and triglyceride. In addition, Diaspirin Cross-linked Hemoglobin interfered with measurement of L-lactate using the ACA IV and minor interference was noted with glucose measured using the Beckman CX3. Data from the interference studies was graphically displayed in the form of interference plots. These plots show the maximum allowable test error, due to Diaspirin Cross-linked Hemoglobin, as a function of analyte and interferent concentrations. Evaluation of the potential interference effect of hemoglobin-based oxygen carrier solutions with use of multiple regression analysis and graphical display of the resultant data in the form of interference plots allows for more reliable reporting of test results from specimens containing these products.

Simplified interpretative format for assessing test interference: studies with hemoglobin-based oxygen carrier solutions.

Substances such as hemoglobin that interfere with analytical processes are recognized as a frequent source of error in laboratory medicine. Standard guidelines for assessment of test interferences assume that interference effects are not related to the concentration of the analyte being measured. However, previous investigations have demonstrated that interference effects can be markedly different, depending on the concentrations of interferent and analyte within the specimen. An experimental protocol for investigating these different types of interference effects has been developed. This protocol utilizes an orthogonally arranged matrix with progressively increasing concentrations of analyte and interferent. Evaluation of the measured analyte concentrations in specimens within the matrix using multiple regression analysis allows the magnitude, direction, and significance of each type of interference to be determined. Unfortunately, implementation of the interference data derived from the multiple regression analysis for judging the clinical acceptability of test results when an interferent is present is difficult. We describe a two-dimensional graphical format for evaluating the clinical acceptability of test results, based on criteria established under the Clinical Laboratory Improvement Amendments of 1988, in specimens containing hemoglobin-based oxygen carrier solutions.

Enzymatic markers of gallstone-induced pancreatitis identified by ROC curve analysis, discriminant analysis, logistic regression, likelihood ratios, and information theory.

We investigated the diagnostic utility of frequent serial determinations of aspartate aminotransferase, alanine aminotransferase (ALT), lipase, amylase, and the lipase/amylase (L/A) ratio for distinguishing patients with acute pancreatitis due to biliary obstruction from those with acute pancreatitis due to other pathogenesis. Analyzed were enzyme activities obtained at admission and peak enzyme activities identified retrospectively from serial measurements in 53 patients with acute pancreatitis due to various causes. We evaluated the data with multiple statistical tools. Discriminant analysis and logistic regression revealed the diagnostic significance of ALT at initial and peak values, and the maximum information provided by peak ALT was confirmed by both logistic regression and stratum-specific likelihood ratios. Stratum-specific likelihood ratios showed peak ALT > 150 U/L was highly diagnostic of biliary pancreatitis. The L/A ratio, either at admission or at peak, was the only other significant variable for identifying patients with acute pancreatitis due to biliary obstruction. A multivariate logistic discriminant function including ALT and the L/A ratio significantly discriminated biliary acute pancreatitis from pancreatitis due to other causes. Evaluation of initial and peak enzyme data by information theory revealed that the optimal test depended on disease prevalence. Initial ALT activities were the test of choice for identifying biliary pancreatitis, up to a disease prevalence of approximately 0.75. At disease prevalence > 0.75, the initial L/A ratio provided the greatest amount of diagnostic information.

Diagnostic accuracy of pancreatic enzymes evaluated by use of multivariate data analysis.

We analyzed pancreatic enzyme data from 508 patients with suspected pancreatitis by neural network analysis, by an Expert multirule generation protocol, and by receiver-operator characteristic (ROC) curve analysis of a single test result. Neural network analysis showed that use of lipase provided the best means for diagnosing pancreatitis. Diagnostic accuracies achieved by using amylase only, lipase only, and amylase and lipase in combination were 76%, 82%, and 84%, respectively. Use of the Expert rule generation protocol provided a diagnostic accuracy of 92% when rules for single and multiple samplings were combined. ROC curve analysis for initial enzyme activities showed the maximal diagnostic accuracy to be 82% and 85% for amylase and lipase, respectively; use of peak enzyme activities yielded accuracies of 81% and 88%, respectively. The evaluation of laboratory test data should include analysis of the diagnostic accuracy of laboratory tests by multivariate techniques such as neural network analysis or an Expert systems approach. Multivariate analysis should allow for a more realistic assessment of the diagnosis accuracy of laboratory tests because all the available data are included in the evaluation.

Laboratory error undetectable by customary quality control/quality assurance monitors.

The preanalytical, analytical, and postanalytical rates of laboratory error have not been studied extensively. We evaluated the preanalytical, analytical, and postanalytical components of laboratory error in 438 consecutive samples submitted to a clinical chemistry laboratory for measurement of creatinine concentrations in plasma. We performed red blood cell antigen determinations to establish patient-sample identity, repeated analysis of creatinine in duplicate to detect analytical error, and tracking of patient specimens from receipt by the laboratory to entry of the laboratory result in the patient's information system record. We found a total error rate of 9.36%. A breakdown of the total error rate into its preanalytical, analytical, and postanalytical components revealed error rates of 0.00%, 8.90%, and 0.46%, respectively. These results suggest that preanalytical and postanalytical error, which are not usually detectable by common quality control strategies, are not major sources of laboratory error. Further work is needed to reduce the unacceptably high rate of analytical errors.

A comprehensive evaluation of the performance of duplicate prothrombin time and activated partial thromboplastin time assays.

An evaluation of the performance of duplicate prothrombin time (PT) and activated partial thromboplastin time (aPTT) assays was undertaken to develop analytical duplicate performance criteria in order to quantitate the risks associated with singlet versus duplicate procedures. Data were retrospectively collected from two hospital laboratories using two different coagulation systems. Included in the study were 6,391 patient samples; 3,047 PT, 3,334 aPTT, for a total of 12,782 data points. If a difference between duplicates of 5% or less is deemed analytically (or clinically) insignificant for PT, then fewer than 1% of the samples analyzed by either laboratory would require duplicates. If a difference between duplicates of 15% or less is deemed analytically (or clinically) insignificant for aPTT, then fewer than 2% of samples would exceed this limit for laboratory A, but 6.0% of samples from laboratory B exceeded this limit.

Cobalamin malabsorption in three siblings due to an abnormal intrinsic factor that is markedly susceptible to acid and proteolysis.

Three siblings presented in their second year of life with megaloblastic anemia that responded to parenteral cobalamin (Cbl). Schilling tests were less than 1%, correcting to 5 to 15% after addition of hog intrinsic factor (IF). Gastric acid analysis and gastric biopsies were normal by light and electron microscopy. Gastric juice contained less than 3 pmol/ml of Cbl-binding ability due to IF (normal, 10-34 pmol/ml) and less than 2 pmol/ml of IF when measured with a radioimmunoassay (RIA) using normal human IF-[57Co]Cbl and rabbit anti-human IF serum (normal, 17-66 pmol/ml). However, RIA employing rabbit anti-hog IF serum gave values of 4-13 pmol/ml of IF (normal, 11-33 pmol/ml). This material had an apparent molecular weight of 40,000 (normal IF = 70,000). The IF from gastric biopsies appeared normal in terms of Cbl-binding ability, ileal binding, molecular weight, and both RIAs. This IF differed from normal mucosal IF, in that it lost its Cbl-binding ability when incubated at 37 degrees C at acid pH or in the presence of pepsin or trypsin. This loss was retarded when [57Co]Cbl was bound to the IF before these incubations. The stabilizing effects of neutralization and Cbl were also demonstrated in vivo. Schilling tests for the siblings of 0.4, 0.5, and 1.0% increased to 2.7, 5.7, and 4.3% (P less than 0.05), respectively, when the Schilling tests were repeated with the addition of NaHCO3 and cobinamide (which allows Cbl to bind immediately to IF). We conclude that Cbl malabsorption in these children is due to an abnormal IF that is markedly susceptible to acid and proteolytic enzymes which cause a decrease in its molecular weight and Cbl-binding ability and a loss of antigenic determinants that are recognized by the anti-human IF serum.

Laboratory equipment maintenance contracts.

The increasing level of technical sophistication and complexity found in clinical laboratory instrumentation today more than ever demands careful attention to maintenance service needs. The time-worn caution for careful definition of requirements for acquisition of a system should also carry over to acquisition of maintenance service. Guidelines are presented for specifications of terms and conditions for maintenance service from the perspective of the laboratorian in the automated clinical laboratory.