Anti-i causing acute hemolysis following a negative immediate-spin crossmatch

A unique case of acute hemolysis following transfusion of red cells (RBCs) that were found compatible by immediate-spin (IS) crossmatch technique is reported. Screening tests for unexpected antibodies, using low-ionic-strength saline (LISS), 10 minutes' incubation at 37 degrees C, and anti-IgG, were nonreactive; however, 1 transfused unit was found crossmatch incompatible by indirect antiglobulin technique (IAT). An anti-i (titer 512 at 4 degrees C) that was not an autoantibody was identified in the patient's serum. Unlike the incriminated donor RBCs, most I+ RBCs did not react by LISS-IAT. Variable reactivity was seen with ficin-treated I+ RBCs, and there was marked hemolysis of iadult and icord RBCs. In marked contrast, dominant Lu(a-b-) RBCs, with reduced expression of i, did not react by any test method; nor did autologous I+, Lu(b+) RBCs. The in vivo clinical significance of this anti-i was confirmed by monocyte monolayer assay and RBC survival studies. The patient's i antigen may have been altered, by either chemotherapy or disease, and lacked part of the i antigen-mosaic. Her antibody was directed at epitopes of i that were absent from her RBCs. Those i epitopes missing from her RBCs are also absent on dominant Lu(a-b-) RBCs. This anti-i represents a unique cause of an acute hemolytic transfusion reaction. It also represents a case of acute immune-mediated hemolysis following transfusion of IS crossmatch-compatible blood when screening tests for unexpected antibodies are nonreactive. Because of the rarity of such cases (less than 1/200,000 RBC units transfused), modifications to pretransfusion testing protocols are not proposed.     

Effect of delayed centrifugation or reading on the detection of ABO incompatibility by the immediate-spin crossmatch

The immediate-spin (IS) crossmatch is a method that detects ABO incompatibility. However, under certain circumstances, this test may show unwanted negative or weak results, even though the red cells (RBCs) and serum being tested are ABO incompatible with each other. The present study investigated the potential effect of delayed centrifugation or reading on the IS crossmatch test performance. When the centrifugation step of the IS crossmatch between group O sera and group A1 RBCs was delayed for 2 minutes, 5 of 200 crossmatches showed no agglutination with only trace (n = 2) or moderate (n = 3) hemolysis, and one crossmatch showed only weak, macroscopic agglutination, but moderate hemolysis. All six sera contained A antibodies that were lytic in vitro and, therefore, probably were capable of causing in vivo hemolysis of transfused A1 RBCs. Delaying the reading of the IS crossmatch test for 2 minutes had no apparent effect on test performance. These data demonstrate the importance of technologists' recognition of hemolysis as a positive result on IS crossmatches, especially if the performance of the centrifugation step of the test is delayed. Furthermore, the unwanted negative agglutination results were abolished by suspending the group A1 RBCs in saline containing EDTA. The authors' laboratory has modified its IS crossmatch procedure so that donor RBCs are routinely suspended in saline containing EDTA before testing. This procedural change should increase the safety of the IS crossmatch.     

The sensitivity and specificity of Brucella agglutination tests

Brucellosis is a systemic infectious disease caused by Gram-negative bacilli, the genus Brucella, and clinical features are diverse. Therefore, several infectious and non-infectious diseases are considered in its differential diagnosis. In this study, we aimed to determine the positivity rate of Brucella agglutination tests in the culture-positive brucellosis and in diseases mimicking brucellosis clinically.Thirty patients with culture-positive brucellosis, and 280 patients with the diseases mimicking brucellosis clinically (20 with miliary tuberculosis, 33 with malaria, 20 with typhoid fever, 20 with adult-onset Still's disease, 47 with systemic lupus erythematosus, 50 with rheumatoid arthritis, 27 with sarcoidosis, and 63 with active lymphoma) were included in the study. Brucella agglutination tests (Rose-Bengal and Wright) were studied in serum samples of these 310 patients.Both Rose-Bengal and Wright tests (the latter in a titer of 1/160 or higher) were positive in all patients with brucellosis. For the other diseases, the test was slightly positive (1/40) in one patient with malaria and another with non-Hodgkin's lymphoma, and weakly positive (1/20) in a patient with typhoid fever. It remained negative in the remaining.In conclusion, agglutination tests currently used in the diagnosis of brucellosis are very sensitive and specific. Brucellosis can be effectively excluded from the diseases having similar clinical features by the use of agglutination tests.     

The computer crossmatch: a safe alternative to the serological crossmatch

The crossmatch has evolved from including a wide range of techniques through a test purely to eliminate ABO incompatibility (immediate spin) to computer crossmatching in which no serological testing is carried out and validation ensures the correct ABO/RhD type blood is issued. The crossmatch was always considered to be the most important feature of the compatibility test and in particular the antiglobulin phase; however, there are potential risks associated with serological and computer crossmatching including technical and procedural errors. The use of immediate spin and computer crossmatch change the emphasis for safety of the compatibility test from the crossmatch to the antibody screen. UK guidelines have now been published describing the features necessary for the introduction of computer crossmatching. Computer crossmatching is used by many institutions in various countries. It is considered safe practice and brings benefits to the laboratory and the patient. Compatibility testing is only one element of the blood transfusion procedure; the others are equally as important and include correct patient identification at the time of collection of the blood sample and at the administration of the blood transfusion.     

The sensitivity and specificity of seven lumbo-pelvic orthopedic tests and the arm-fossa test

Twenty-nine lumbosacral asymptomatic and 39 symptomatic patients who attended a chiropractic clinic were examined by a practitioner who was blinded to their symptoms. Seven lumbosacral orthopedic tests, along with the arm-fossa test were scrutinized for sensitivity, specificity and diagnostic competency values. Only the arm-fossa test and heel-buttock tests had a significantly higher percentage of positive findings in symptomatic than asymptomatic cases. These same tests were the only ones which could be considered to have an acceptable diagnostic value, when both the sensitivity and specificity were taken into consideration by Youden's index. The number of positive tests was unrelated to the presence of lumbosacral symptoms. Orthopedic tests which appeared to strain several adjacent anatomical structures were most commonly positive. No particular combination of tests could predict if the patient was symptomatic or asymptomatic. Only the heel-buttock test had some predictive value. It appears that these tests were of limited value in differentiating between the symptomatic and asymptomatic subjects who attended the study clinic.     

The evaluation of the sensitivity and specificity of wrist examination findings for predicting fractures

Background

The aim of this study was to evaluate the sensitivity and specificity of physical examination findings and functional tests in adult acute wrist trauma patients who presented to the emergency department (ED) and to create a reliable and practical clinical decision rule for determining the necessity of radiography in wrist trauma.

The sensitivity and specificity of forecasting high-cost users of medical care.

OBJECTIVES: This study compares the ability of 3 risk-assessment models to distinguish high and low expense-risk status within a managed care population. Models are the Global Risk-Assessment Model (GRAM) developed at the Kaiser Permanente Center for Health Research; a logistic version of GRAM; and a prior-expense model. GRAM was originally developed for use in adjusting Medicare payments to health plans. METHODS: Our sample of 98,985 cases was drawn from random samples of memberships of 3 staff/group health plans. Risk factor data were from 1992 and expenses were measured for 1993. Models produced distributions of individual-level annual expense forecasts (or predicted probabilities of high expense-risk status for logistic) for comparison to actual values. Prespecified "high-cost" thresholds were set within each distribution to analyze the models' ability to distinguish high and low expense-risk status. Forecast stability was analyzed through bootstrapping. RESULTS: GRAM discriminates better overall than its comparators (although the models are similar for policy-relevant thresholds). All models forecast the highest-cost cases relatively well. GRAM forecasts high expense-risk status better than its comparators within chronic and serious disease categories that are amenable to early intervention but also generates relatively more false positives within these categories. CONCLUSIONS: This study demonstrates the potential of risk-assessment models to inform care management decisions by efficiently screening managed care populations for high expense-risk. Such models can act as preliminary screens for plans that can refine model forecasts with detailed surveys. Future research should involve multiple-year data sets to explore the temporal stability of forecasts.     

The influence of spacer-containing enzyme conjugate on the sensitivity and specificity of enzyme immunoassays for hapten

BACKGROUND: In hapten enzyme immunoassays (EIA), there is an increase or decrease of labeled hapten recognition by antibody that affects sensitivity of the assay. We incorporated a spacer between a hapten derivative and enzyme to test its influence on the sensitivity and specificity of enzyme immunoassays. METHOD: Antibodies were generated against cortisol-3-O-carboxymethyl-oxime-bovine serum albumin (cortisol-3-O-CMO-BSA) and cortisol-21-hemisuccinate-bovine serum albumin (cortisol-21-HS-BSA) as an immunogen. Four cortisol horseradish peroxidase (HRP) enzyme conjugates were prepared using 2 cortisol derivatives (cortisol-3-O-CMO and cortisol-21-HS) with and without adipic acid dihydrazide (ADH) as a spacer. Eight combinations of homologous and heterologous assays were evaluated. RESULT: The incorporation of ADH spacer in cortisol-enzyme conjugate improved the sensitivity in heterologous (bridge and site plus bridge) EIA systems. In heterologous assays (site plus bridge), the presence of spacer in enzyme conjugate reduced the cross-reactivity with cross-reacting steroids. CONCLUSION: Spacer in the enzyme conjugate for hapten ELISA can improve the sensitivity of heterologous assay of hapten-like steroids. It may also reduce the cross-reactivity for some assays.