Development of lymphocytotoxic and platelet reactive antibodies: a prospective study in patients with acute leukaemia

The value of crossmatch tests and panel tests as a screening tool to predict the outcome of platelet transfusion in a non-selected haematological population of patients

BACKGROUND AND OBJECTIVES

Alloantibodies against platelets can be detected by using different laboratory tests. Most of these tests, which use panel cells or antigens as a target, perform poorly in non-selected haematological patients. In relation to these tests, a crossmatch test of transfused platelets and patient's serum may be viewed as the standard and may be superior in predicting donor platelet destruction by alloimmunization.

MATERIALS AND METHODS

In 95 randomly selected thrombocytopenic patients with haematological malignancies, who were receiving leucodepleted blood products, 184 serum samples were studied in an in vitro crossmatch test by using the technique of the platelet immunofluorescence test (crossmatch-PIFT), in an in vivo crossmatch test detecting in vivo binding of immunoglobulins to transfused platelets according to the PIFT technique (in vivo-PIFT), in the indirect PIFT using five random donors as a target (panel-PIFT) and in an enzyme linked immunosorbent assay using immobilized human leucocyte antigens (HLAs) of 100 standardized donors (ELIHLA). The results of all these methods were related to the recovery at 1 and 16 h post-transfusion.

RESULTS

The results of the crossmatch-PIFT were not associated with platelet recovery at 1 and 16 h after transfusion. Even in a subgroup of patients, in whom predefined clinical factors were excluded, no association with platelet recovery was found. The results of the crossmatch-PIFT correlated with those of the in vivo-PIFT (P = 0.02); however, 35 (19%) discrepant results were identified between these tests. The results of the crossmatch-PIFT were not related to the panel-PIFT (P = 0.25), but did relate to those of the ELIHLA (P = 0.02), still revealing 36 (20%) discrepant results. None of the in vivo-PIFT, the panel-PIFT or the ELIHLA was associated with platelet recovery after 1 h, whilst only a positive panel-PIFT was associated with poor platelet recovery at 16 h after transfusion (P = 0.03).

CONCLUSIONS

In a population at low risk for alloimmunization, the correlation of test outcome and platelet recovery is poor. None of these crossmatch tests or screening tests was identified as superior to any other in this population.

The value of alloantibody detection in predicting response to HLA-matched platelet transfusions

Alloantibody tests demonstrate immunological causes of insufficient increments in random platelet transfusions. The value of a positive or negative test result in predicting the outcome of human leucocyte antigen (HLA)-matched transfusions in patients refractory to leucodepleted random platelet transfusions has not been assessed. We retrospectively evaluated the outcome of the first HLA-matched platelet transfusion in 72 patients with haematological diseases in two ways: first, the strategy according to which the patient was selected for HLA-matched platelet transfusions was analysed. The strategies were: (i) results of alloantibody tests were not available, (ii) a positive alloantibody test, (iii) a negative alloantibody test. Secondly, the outcome of the first HLA-matched transfusion was investigated relative to the results of alloantibody tests, irrespective of the decision strategy. No significant association was found between the decision strategy and the outcome of the first HLA-matched platelet transfusion. Positive alloantibody tests, however, predicted a better outcome of the first HLA-matched platelet transfusion (P = 0.04 and P = 0.03 after 1 and 16 h respectively). In patients refractory to random platelet transfusions, positive alloantibody tests predicted a better outcome of HLA-matched platelet transfusions. Patients with negative alloantibody tests, however, may benefit from HLA-matched platelet transfusions.

Visual scoring versus histogram subtraction of in vivo binding of immunoglobulins against platelets after transfusion

BACKGROUND

We developed a technique, in vivo binding of immunoglobulins in the platelet immunofluorescence test (IVBI-PIFT), that detects immunoglobulins bound in vivo to transfused platelets. The visually scored results of this technique, however, are susceptible to interobserver variation. We describe a more objective method to generate results in IVBI-PIFT.

METHODS

We studied 201 samples in 120 patients with hematologic malignancies in the IVBI-PIFT. Histogram subtraction, i.e., fluorescence (anti-immunoglobulin G and fluorescein isothiocyanate) histogram before platelet transfusion subtracted from the histogram after platelet transfusion, was compared with visual scoring (pattern 1: no enhanced fluorescence before and after transfusion; pattern 2: enhanced fluorescence before and after platelet transfusion; pattern 3: enhanced fluorescence before transfusion; pattern 4: enhanced fluorescence after transfusion, interpreted as alloimmunization). After histogram subtraction, the number of remaining events (events post substraction, EPS) and the mean amount of fluorescence of these remaining events (mean channel post substraction, MCPS) were used and compared with the visual scoring and with platelet survival after transfusion.

RESULTS

In 26 (13%) of the 201 samples studied in the IVBI-PIFT, fewer than three of five observers agreed on the visually scored pattern. In the 175 (87%) remaining samples, histogram subtraction showed a significant differentiation between pattern 4 and patterns 1 and 2 by using EPS, whereas patterns 4 and 3 were distinguished by using MCPS. The combination of EPS and MCPS differentiated best between pattern 4 and patterns 1, 2, and 3 (73% sensitivity, 96% specificity, 79% positive predictive value, and 95% negative predictive value). In contrast, the predictive value for platelet recovery after 1 and 16 h of pattern 4 from the visual scoring method and the results of histogram subtraction were poor.

CONCLUSION

This objective method of histogram subtraction correlated well with the visual scoring method of IVBI-PIFT.

Screening for alloantibodies in the serum of patients receiving platelet transfusions: a comparison of the ELISA, lymphocytotoxicity, and the indirect immunofluorescence method

BACKGROUND

For screening of alloimmunization in patients repeatedly receiving platelet transfusions, different tests are used, none of which is the standard. Here we describe a comparison of four tests most commonly used for detection of alloimmunization in a group of nonselected patients receiving platelet transfusions.

STUDY DESIGN AND METHODS

In 99 patients with hematologic malignancies who received platelet transfusions, 192 random serum samples were tested in the ELISA, the lymphocytotoxic test (LCT), the lymphocyte immunofluorescence test (LIFT), and the platelet immunofluorescence test (PIFT). Results of all tests were compared.

RESULTS

The results of all tests were significantly correlated with each other (p < 0.005). ELISA and LIFT were more often positive than LCT and PIFT. ELISA and LIFT showed the best correlation (chi-square test = 63.7, p < 0.001).

CONCLUSION

ELISA, the least time-consuming test, detects alloimmunization as often as LIFT and more often than LCT and PIFT.

Comparison of a new WBC-reduction system and the standard plateletpheresis protocol in the same donors

BACKGROUND

A cell separator (Spectra, Gambro BCT) with an integrated leukoreduction system (LRS) for producing WBC-reduced single-donor platelet concentrates has been shown to result in a slightly reduced collection efficiency as compared to the former Spectra system without LRS. A novel modified system for improved collection efficiencies (LRS Turbo, Gambro BCT) was evaluated.

STUDY DESIGN AND METHODS

Each of 37 donors underwent plateletpheresis using the LRS Turbo (LRS-T) and the standard LRS (LRS) of the Spectra cell separator. The collection efficiency and WBC contamination of the different techniques were compared. Platelets were counted automatically and WBCs were counted by using one or two full grids of a Nageotte chamber.

RESULTS

The preseparation and postseparation numbers of RBCs, WBCs, and platelets, as well as the number of collected platelets, did not differ for the two techniques. In the LRS-T separations, the collection efficiency was 112 percent of that in the LRS procedures. Median residual WBCs in the platelet components were 0.0256 x 10(6) per LRS-T procedure and 0.0253 x 10(6) per LRS procedure. The purity of the LRS-T components was not less than that of the standard LRS components, whereas the collection efficiency of the LRS-T was significantly greater, 44.9 percent versus 40.7 percent.

CONCLUSIONS

The LRS-T procedures produced platelet concentrates with WBC-reduction capacity that is comparable to that obtained with the standard LRS procedures, which have previously been described as satisfying the most stringent criteria for WBC-reduced platelets. The new technique significantly improved the collection efficiency of the plateletpheresis procedure.

Selecting donors of platelets for refractory patients on the basis of HLA antibody specificity

BACKGROUND

Patients who are refractory to platelet transfusion as a result of HLA alloimmunization are generally given HLA-matched or crossmatched platelets. However, HLA-matched platelets that are matched at HLA-A and -B loci (A-matched) or those without any mismatched or cross-reactive antigens (BU-matched) are frequently unavailable. A disadvantage of crossmatching is that crossmatched platelets have a shelf life of only 5 days, so that crossmatch tests must be performed frequently for patients requiring long-term platelet transfusions. An alternative method is the selection of platelets according to the patient's HLA antibody specificity, called the antibody specificity prediction (ASP) method.

STUDY DESIGN AND METHODS

An anti-human globulin-enhanced microlymphocytotoxicity test modified by a double addition of serum and a computer program were used to determine the specificity of patients' HLA antibodies. Platelet crossmatching was performed with a solid-phase adherence assay. The percentage of platelet recovery (PPR) was determined in 1621 platelet transfusions in an observational study in 114 patients, and the PPR of platelets selected by the ASP method was compared with the PPR of those that were HLA-matched, crossmatched, or randomly selected. The numbers of potential donors in files of HLA-typed donors as identified by HLA matching vs. the ASP method were determined.

RESULTS

After adjustments for covariates, the mean +/- SEM PPR was similar for HLA-matched (21 +/-4%), cross-matched (23+/-4%), and ASP-selected (24+/-3%) platelets and was significantly lower for randomly selected (15+/-1.4%) platelets. For 29 alloimmunized HLA-typed patients, the mean number of potential donors found in a file of 7247 HLA-typed donors was 6 who were an HLA-A match (median = 1), 33 who were an HLA-BU match (median = 20), and 1426 who were identified by the ASP method (median = 1365).

CONCLUSION

The ASP method of donor selection for refractory alloimmunized patients appears as effective as HLA matching or crossmatching. Far more donors are identified in a file of HLA-typed donors by the ASP method than by HLA matching, and this indicates that the ASP method provides important advantages regarding the availability of compatible platelet components.

Practice parameter for the recognition, management, and prevention of adverse consequences of blood transfusion. College of American Pathologists

No Abstract Available

Platelet alloimmunization after transfusion. A prospective study in 117 heart surgery patients

BACKGROUND AND OBJECTIVES

The frequency of platelet-specific antibodies after one series of blood transfusions has not been reported, and in multiply transfused patients is controversial.

MATERIALS AND METHODS

We studied the frequency of alloimmunization against platelet antigens in 117 patients who received a single series of blood transfusions. They received mostly saline-adenine-glucose+mannitol red blood cell components (poor in leukocytes and platelets) in connection with cardiac surgery. Platelet-specific antibodies were detected with the platelet ELISA and the monoclonal-antibody-specific immobilization of platelet antigen assay. HLA antibodies were detected by the standard lymphocyte cytotoxicity techniques.

RESULTS

We found platelet-specific anti-HPA-5b (anti-Bra) in 2 cases (1.7%). One antibody was the result of de novo immunization. We detected lymphocytotoxic HLA antibodies in 21 patients (17.9%), of whom 18 (15.4%) had had no detectable antibodies before transfusion. There was a positive correlation between the transfused load of immunogenic materials and the frequency of alloimmunization against HLA antigens. In one third of the immunized patients, there was no history of previous immunization.

CONCLUSION

There was a low incidence of platelet-specific antibodies after one series of blood transfusions in this group of patients. This is similar to the results of some previous studies in multiply transfused patients, but not with those of others who found a higher incidence.

Leukocyte-depleted blood components prevent platelet refractoriness in patients with acute myeloid leukemia

Platelet refractoriness arising from HLA immunization develops in 20-50% of multitransfused patients with hematologic malignancies. We retrospectively analyzed the efficiency of leukocyte-depleted blood components in preventing refractoriness in 140 adult patients with acute myeloid leukemia (AML), treated according to a standardized cytostatic protocol. Sixty-eight patients received leukocyte-depleted (L-D) platelet concentrates (PCs) and red cells (RBCs), with fewer than 10(6) leukocytes per unit, and 72 patients received standard (STD) blood components. Two of 67 (3%) evaluable patients in the leukocyte-depleted group and 14 of 68 (21%) in the standard group became refractory during the median follow-up time of 229 days. Nine of 24 (37%) previously pregnant women in the STD group but none of 17 in the L-D group became refractory. Twenty patients were shifted during later treatment from L-D to STD PCs; none became refractory. Corrected platelet increments (CI) at 18 hours were higher after STD PCs (6.50 than L-D PCs (5.2), but more PCs and RBCs were transfused per patient in the STD group. It is concluded that effective leukocyte depletion prevents platelet refractoriness in patients with AML, even in those with previous immunization, and reduces the consumption of blood components.

Serological screening, using three different test systems of platelet-transfused patients with hematologic-oncologic disorders

Sera of hematologic-oncologic patients were tested regularly after platelet transfusions in three test systems: lymphocytotoxicity test, platelet adhesion immunofluorescence test, and--only selected sera--in the monoclonal antibody-specific immobilization of platelet antigen test. Of 388 patients 53 (14%) had HLA antibodies 5 of these in combination with platelet-specific alloantibodies. Lymphocyte-restricted (non-HLA) reactions were observed in 20 patients, the majority of which was attributed to lymphocyte-specific auto- or alloantibodies. Sera of 27 patients showed platelet-specific reactions, usually cold-reacting autoantibodies which have no effect in vivo.

Platelet alloimmunization after multiple transfusions: a prospective study of 50 patients

Fifty polytransfused patients were prospectively studied to determine the frequency of post-transfusion alloimmunization and its influence on the response to platelet transfusion. Platelet- and HLA-specific antibodies were detected by means of the standard and antiglobulin-augmented lymphocytotoxicity techniques (LCT), the platelet suspension indirect immunofluorescence test (PSIIFT), and monoclonal antibody immobilization of platelet antigens (MAIPA). HLA antibodies were detected in 13 patients (26%) (IgM = 6; IgG = 6; IgM + IgG = 1). The standard LCT was positive in 12 of these 13 patients. Complement-independent HLA antibodies, only detectable in the PSIIFT and the antiglobulin-augmented LCT, were documented in two patients and were associated with poor post-transfusion platelet recovery in the patient who could be evaluated. All the HLA antibodies were detected in the PSIIFT, while only four were detected in the MAIPA. Platelet-specific alloantibodies were found in two patients by means of PSIIFT or MAIPA and may have led to poor post-transfusion platelet recovery in one patient. Platelet autoantibodies were detected in two patients but were not associated with platelet refractoriness. Paraformaldehyde-dependent platelet antibodies were detected in 11 patients but were not associated with platelet refractoriness.

HLA antibodies--the cause of platelet alloimmunization in Chinese

Lymphocytotoxicity test (LCT) and platelet suspension immunofluorescence test (PSIFT) were used together to screen platelet-associated antibodies in patients who received long-term platelet transfusion. Twenty-four of 53 patients (45.3%) were immunized subsequently. Since the concordance of LCT and PSIFT was 100%, most of the platelet associated antibodies were of HLA specificity, and platelet specific antibody alone (in absence of HLA) was not detected. The identified antibodies were anti-A2, A11, A24, B5, B46, B57, B60, and B62. The majority of them were against the high frequency HLA antigens in the Chinese population. The development of antibody could not be correlated with the number of platelet-donors exposed, the time interval after the initiation of platelet transfusion, or the percentage of reactive lymphocytotoxic panels. HLA antibody was the major factor in causing platelet alloimmunization in the Chinese patients. However, some other unknown factors should be looked for. In addition, ABO incompatibility did not affect the posttransfusional increment while the platelet was compatible with LCT crossmatching.