Evaluation of different testing methods for identification of RhIG in red blood cell antibody detection

Transfusion Blood Bank (Recipient) Testing

Pretransfusion and post-transfusion recipient testing are routine blood bank functions. This article presents a review of request and sample requirements, routine and extended typing and antibody evaluation, and post-transfusion circumstances requiring additional work-up. Although the regimented approach of blood banking fundamentals may be viewed as tedious, these steps are defined and designed to prevent potentially fatal ABO-incompatible transfusions and improve the overall safety of transfusion medicine patients.

Implementation of a Standardized Prenatal Testing Protocol in an Integrated, Multihospital Health System

OBJECTIVES

When our institution grew into an integrated multihospital health system, we were faced with the need to standardize laboratory processes, including blood bank processes, across all locations. The purpose of this article is to describe our experience of standardizing the protocols for prenatal testing.

METHODS

For each hospital in the system, we established service tiers to define tests offered on site or referred to another location. For each prenatal test, we examined the related processes for ways to improve uniformity, efficiency, and reliability. Throughout this process of standardization, we collaborated with the clinical services to gain concurrence on the interpretation and reporting of results.

RESULTS

We created and implemented a uniform protocol for testing prenatal patients. The protocol standardized the definition of critical titer, instituted criteria to identify passively acquired anti-D, and established a process for the follow-up of women with inconsistent serologic results on Rh(D) typing.

CONCLUSIONS

Close collaboration with the clinical services ensured that our testing protocol is aligned with the needs of the integrated obstetrics service in the health system. The approach described in this article may provide a plan outline for pathologists facing similar challenges at other integrated health systems.

Very Prolonged Anti-D: Confusion Surrounding Alloimmunization After Extra Rh Immunoglobulin: A Case Report

BACKGROUND

Rh immunoglobulin (RhIg) is usually detectable a maximum of 12 to 14 weeks after administration. Positive antibodies beyond this time frame suggests alloimmunization.

CASE

A woman had three pregnancies over a 6-month period, with two first-trimester losses. She received RhIg in the first pregnancy but not in the second. Two months after the second loss, in her third pregnancy, she received RhIg at week 6 due to first-trimester bleeding. She was subsequently anti-D antibody positive up to week 28 with antibodies too low to titre, leading to confusion about whether alloimmunization had occurred.

CONCLUSION

Rh Ig administration led to positive anti-D antibodies lasting 22 weeks, suggesting keeping this differential diagnosis in mind when suspecting alloimmunization with positive antibodies at levels too low to titre.

Comparison of two column agglutination tests for red blood cell antibody testing

Background

Several sensitive methods are available for red blood cell (RBC) antibody screening. Among these, gel and glass card systems have demonstrated comparably good performance in retrospective studies and are widely used in routine patient diagnostics, but their performance in prospective studies has not been sufficiently characterised.

Patients and methods

Gel card (Bio-Rad DiaMed) and glass bead-based (Ortho Clinical Diagnostics) column agglutination technologies were used to screen for antibodies prospectively (group A) and for antibody identification in stored and fresh samples known to contain RBC antibodies retrospectively (group B). Untreated reagent RBCs and either papain-treated (Bio-Rad) or ficin-treated panel C cells (Ortho) were used for antibody identification.

Results

RBC-reactive antibodies were detected in 22 of 1000 group A samples, three of which tested positive only by gel card agglutination, and four only by glass bead agglutination (including one false positive each). Group B comprised 202 sera with known antibodies: 33 of these samples contained 36 antibodies detected only by gel card agglutination, whereas 9 samples contained antibodies detectable only by glass bead-based agglutination. Discrepancies mostly involved weak antibodies reactive by enzyme only. Two sera contained antibody mixtures that neither system detected completely. Of note, in antibody differentiation batches one and two, anti-Lu^a was reactive in 7 of 7 and 1 of 8 samples, respectively.

Conclusion

Both column agglutination tests for red cell antibodies had equal sensitivity and specificity with unstored samples. In stored samples, weak and enzyme-only antibodies were more frequently detected with the gel card system.

Patient factors associated with unidentified reactivity in solid-phase and polyethylene glycol antibody detection methods

BACKGROUND

Several publications have reported an increase in nonspecific reactions when automated technologies such as solid phase are used for the detection of red blood cell alloantibodies. However, there is little known about patient-specific factors associated with these reactions and the clinical importance of these nonspecific reactions.

STUDY DESIGN AND METHODS

We performed a 6-year retrospective review of our blood bank records and all newly reported unidentified (UID) reactivity using a test tube polyethylene glycol (t-PEG) and solid-phase method for the detection and identification of alloantibodies was recorded. Patient factors, such as underlying diagnosis, age, sex, ABO, Rh type, ethnicity, and subsequent antibody formation were recorded in each case.

RESULTS

We determined that there was a significant increase in new UID reactions recorded in solid phase (20 per 10,000 tests) when compared to the t-PEG (1.8 per 10,000 tests) method for the detection of antibodies (p ≤ 0.0001). Solid-phase UID reactions were significantly associated with female sex (p = 0.04) and certain diagnoses, such as chronic or autoimmune disease, cancer, pregnancy, surgery, and trauma. Approximately 16% of patients developed a new auto- or alloantibody subsequent to their detected UID using solid phase.

CONCLUSIONS

When solid phase is used for antibody identification, there is greater sensitivity toward nonspecific reactivity when compared to the t-PEG method. Patient sex and underlying diagnosis may explain the increased incidence of new UID reactivity in the solid-phase technology. Finally, UID reactivity should not be overlooked due to a notable percentage of subsequent clinically significant antibodies after UID detection.