Flow cytometric analysis in platelet crossmatching using a platelet suspension immunofluorescence test

Fetal and neonatal alloimmune thrombocytopenia - The Norwegian management model

In Norway, the management strategy for fetal and neonatal alloimmune thrombocytopenia (FNAIT) has for more than two decades differed from most other countries. The focus of this paper is to describe and discuss the Norwegian FNAIT management program. We recommend antenatal IVIg to women who previously have had a child with FNAIT-induced ICH, and usually not to HPA-1a alloimmunized pregnant women where a previous child had FNAIT, but not ICH. When deciding management strategy, we use not only the obstetric history but also the antenatal anti-HPA-1a antibody level as a tool for risk stratification. The Norwegian National Unit for Platelet Immunology (NNUPI) at the University Hospital of North Norway in Tromsø provides diagnostic and consulting service for the clinicians and the blood banks all over the country, and serves as a national reference laboratory for FNAIT investigations.

Flow cytometry antibody screening using pooled red cells

BACKGROUND

For red cell alloantibody screening, the column agglutination technique (CAT) is used extensively, and flow cytometry (FC) screening has recently been demonstrated to be accurate, rapid, and cost effective. We attempted to determine whether the high sensitivity of FC allows pooling of screening red cells, which is generally not an acceptable technique in CAT.

METHODS

For FC screening, a commercial two-cell screening panel was utilized for the preparation of individual cells (CSi), as well as pooled cells diluted 1 in 2 (CSp), and 1 in 3 (CS1/3). Another panel was pooled from 120 randomly selected group O donors (RSp).

RESULTS

Comparing the endpoint titrations of serial dilutions, CS1/3 was found to be one dilution, on the average, less sensitive than CSi. In 33 CAT-positive patient samples, the sensitivities of CSi and CSp did not differ significantly without polyethylene glycol (PEG) (30/33, 26/33, respectively, P = 0.125), although they did differ significantly with PEG (32/33, 25/33, respectively, P = 0.016). The percentages of reactive cells among the total cells from RSp were roughly proportional to the relevant antigen frequencies of the local donors.

CONCLUSIONS

A trend toward reduced sensitivity was observed using pooled red cells, even via FC. Pooled cells from randomly selected group O donors may be employed as another method by which the characteristics of known antibodies might be assessed.

Gastrointestinal bleeding in the cancer patient

Gastrointestinal bleeding is a common occurrence in patients with cancer and is a frequent indicator of a gastrointestinal malignancy. Rapid evaluation and treatment is key for the hemodynamically unstable patient. Endoscopy remains the cornerstone of diagnosis and management for cancer patients with gastrointestinal bleeding. The emergency physician should also be aware of other diagnostic and treatment modalities that may be needed to take care of these patients.

A screening and intervention program aimed to reduce mortality and serious morbidity associated with severe neonatal alloimmune thrombocytopenia

The study's objective was to identify HPA 1a-negative women and to offer them an intervention program aimed to reduce morbidity and mortality of neonatal alloimmune thrombocytopenia (NAIT). HPA 1 typing was performed in 100 448 pregnant women. The HPA 1a-negative women were screened for anti-HPA 1a. In immunized women, delivery was performed by Cesarean section 2 to 4 weeks prior to term, with platelets from HPA 1a-negative donors reserved for immediate transfusion if petechiae were present and/or if platelet count was less than 35 x 10(9)/L. Of the women screened, 2.1% were HPA 1a negative, and anti-HPA 1a was detected in 10.6% of these. One hundred seventy pregnancies were managed according to the intervention program, resulting in 161 HPA 1a-positive children. Of these, 55 had severe thrombocytopenia (< 50 x 10(9)/L), including 2 with intracranial hemorrhage (ICH). One woman with a twin pregnancy missed the follow-up and had one stillborn and one severely thrombocytopenic live child. In 15 previous prospective studies (136 814 women) there were 51 cases of severe NAIT (3 intrauterine deaths and 7 with ICH). Acknowledging the limitation of comparing with historic controls, implementation of our screening and intervention program seemed to reduce the number of cases of severe NAIT-related complications from 10 of 51 to 3 of 57.

Life-threatening adverse reaction followed by thrombocytopenia after passive transfusion of fresh frozen plasma containing anti-CD36 (Naka) isoantibody

BACKGROUND

Anti-CD36 isoantibody in blood recipients is reported to cause refractoriness to platelet (PLT) transfusions and posttransfusion purpura-like syndrome. There are few reports, however, about the effects of passively transfused blood products containing this isoantibody on recipients.

CASE REPORT

A 67-year-old Japanese woman underwent brain surgery. On the 6th postoperative day, the patient experienced tightness of the chest and nausea after receiving a transfusion of fresh frozen plasma (FFP). When she manifested hypotension, the transfusion was discontinued. No cutaneous manifestation was observed. The patient's condition gradually improved soon after the administration of steroids.

RESULTS

Her pretransfusion PLT count was 17.1 x 10(4) per microL. It decreased to 1.9 x 10(4) per microL 12 hours after transfusion and recovered to 15.4 x 10(4) per microL 8 days after transfusion. The donor of the FFP had a Type I CD36 deficiency. Flow cytometric analysis identified anti-CD36 isoantibody in the FFP. The cross-match between the patient's PLTs and the FFP was positive. The FFP induced the aggregation of PLTs derived from healthy adults.

CONCLUSION

This is the first reported case of life-threatening adverse effects and thrombocytopenia caused by passively transfused anti-CD36 isoantibody. The possibility of passive infusion of this antibody should be considered in the evaluation of life-threatening transfusion reactions followed by thrombocytopenia.

Improved method for fluorescence cytometric immunohematology testing

BACKGROUND

A method for accurate immunohematology testing by fluorescence cytometry (FC) was previously described. Nevertheless, the use of vacuum filtration to wash RBCs and a standard-flow cytometer for data acquisition hindered efforts to incorporate this method into an automated platform.

STUDY DESIGN AND METHODS

A modified procedure was developed that used low-speed centrifugation of 96-well filter plates for RBC staining. Small-footprint benchtop capillary cytometers (PCA and PCA-96, Guava Technologies, Inc.) were used for data acquisition. Authentic clinical samples from hospitalized patients were tested for ABO group and the presence of D antigen (n = 749) as well as for the presence of RBC alloantibodies (n = 428). Challenging samples with mixed-field reactions and weak antibodies were included. Results were compared to those obtained by column agglutination technology (CAT), and discrepancies were resolved by standard tube methods. Detailed investigations of FC sensitivity and reproducibility were also performed.

RESULTS

The modified FC method with the PCA determined the correct ABO group and D type for 98.7 percent of 520 samples, compared to 98.8 percent for CAT (p > 0.05). No-type-determined (NTD) rates were 1.2 percent for both methods. In testing for unexpected alloantibodies, FC determined the correct result for 98.6 percent of 215 samples, compared to 96.3 percent for CAT (p > 0.05). When samples were automatically acquired in the 96-well plate format with the PCA-96, 98.7 percent of 229 samples had correct ABO group and D type determined by FC, compared to 97.4 percent for CAT (p > 0.05). NTD rates were 0.9 and 2.6 percent, respectively. Antibody screens were accurate for 99.1 percent of 213 samples with the PCA-96, compared to 99.5 percent for CAT (p > 0.05). Further investigations demonstrated that FC with the PCA-96 was better than CAT at detecting weak anti-A (p < 0.0001) and alloantibodies.

CONCLUSIONS

An improved method for FC immunohematology testing has been described. This assay was comparable in accuracy to standard CAT techniques, but had better sensitivity for detecting weak antibodies and was superior in detecting mixed-field reactions (p < 0.005). The FC method demonstrated excellent reproducibility. The compatibility of this assay with the PCA-96 capillary cytometer with plate-handling capabilities should simplify development of a completely automated platform.

An automatable format for accurate immunohematology testing by flow cytometry

BACKGROUND

Current immunohematology testing methods have limitations including cost, throughput, and adaptability to automation. Furthermore, current automated and semiautomated workstations cannot accommodate many other tests relevant to blood transfusion.

STUDY DESIGN AND METHODS

Authentic clinical samples from hospitalized patients were tested for ABO group, D type, and presence of RBC alloantibodies by column agglutination technology (CAT), standard tube methods, and a recently developed flow cytometry (FC) technique. Included were challenging samples with rouleaux, autoantibodies, mixed-field reactions, and weak antibodies. Antibody staining of RBCs for FC was initially performed in test tubes and subsequently in microtiter filter plates interfaced with a vacuum manifold.

RESULTS

When antibody staining was performed in tubes, FC testing determined the correct ABO group and D type for 99.1 percent of 222 clinical samples, as compared to accuracies of 91.9 percent for CAT and 95.0 percent for standard tube testing. FC testing also detected 99.5 percent of clinically relevant RBC alloantibodies in 239 patient samples, as compared to 98.9 percent for CAT and 94.7 percent for LISS-IAT. Using the FC filter plate technique, 104 of 109 samples (95.4%) were correctly typed for ABO and D (the remaining five samples were read as "no type determined" due to RBC and serum testing discrepancies), and RBC alloantibodies of the IgG and IgM classes were correctly identified in 98.3 percent of samples.

CONCLUSIONS

Optimized FC testing methods that are comparable in accuracy to standard CAT and tube methods are described. When used with filter plates, this methodology should allow rapid and cost-effective immunohematology testing of both patient and donor samples in an automated workstation format. The same workstation should support automation of other pretransfusion assays that can be analyzed by FC.

Flow cytometric monocyte phagocytic assay for predicting platelet transfusion outcome

BACKGROUND

A new flow cytometric monocyte phagocytic assay (FMPA) was developed with 5-chloromethyl fluorescein diacetate (CMFDA)-labeled platelets for predicting the outcome of platelet transfusion.

STUDY DESIGN AND METHODS

Twelve patients with a history of multiple platelet transfusions and 21 controls were enrolled in this study. Platelets labeled with CMFDA were incubated with patient serum and then incubated with monocytes. They were then analysed by flow cytometry. Monocytes that had phagocytized platelets (%) were detected as a CMFDA-positive platelet population with a CD14+ monocyte gate. The performance of FMPA was evaluated in 29 transfusions by 1- and 24-hour CCIs and platelet crossmatching.

RESULTS

FMPA results were well correlated with 1-hour (r = -0.818, p = 0.001) and 24-hour (r = -0.782, p = 0.001) CCIs. In the group with high FMPA results (mean +/- SD, 79.1 +/- 7.3%), nine of 10 positive crossmatches revealed low CCIs, and six of seven negative crossmatches revealed high CCIs. The CCI predictability of crossmatching in the group with high FMPA results was high (88.2%). In the group with low FMPA results (mean +/- SD, 34.6 +/- 7.8%), all 12 transfusions revealed high CCIs even though in four transfusions there were positive results in both platelet antibody testing and platelet crossmatching.

CONCLUSION

FMPA is designed with near in vivo conditions to measure an immune response to transfused platelets, including phagocytosis. This is a useful method for predicting the outcome of platelet transfusion.

Use of HLA- and HPA--matched platelets in alloimmunized patients

Refractoriness for platelet transfusion is mostly due to clinical factors but may also be caused by alloimmunization. Use of leukocyte-depleted blood cells for transfusions of patients with hematological diseases has reduced if not eliminated HLA-alloimmunization. HLA-antibodies reduce the survival time of incompatible platelets complicating seriously the platelet transfusion support in at least 5% of patients. If consecutive transfusions of HLA matched platelets also fail without identifiable clinical causes, HPA-alloimmunization may have occurred. Platelets from donors phenotyped for both HLA and HPA may produce good platelet count increments and allow optimal treatment of the basic disease despite broad spectrum alloimmunization. Additional cross-matching of phenotyped platelets with patient serum may be needed to circumvent platelet-specific antibodies of unknown specificity.