|LETTER TO EDITOR
|Year : 2018 | Volume
| Issue : 2 | Page : 140-141
Reagent-dependent reactivity: A noise in the immunohematology laboratory
Department of Transfusion Medicine, Kovai Medical Center and Hospital, Coimbatore, Tamil Nadu, India
|Date of Web Publication||24-Oct-2018|
Dr. Rajeswari Subramaniyan
Department of Transfusion Medicine, Kovai Medical Center and Hospital, Coimbatore, Tamil Nadu
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Subramaniyan R. Reagent-dependent reactivity: A noise in the immunohematology laboratory. Glob J Transfus Med 2018;3:140-1
We received a blood grouping request for a 30-year-old primigravida at 12 weeks of gestation as a part of the routine antenatal workup. Blood grouping was done using fully automated blood grouping system (IH-500, Bio-Rad, Cressier, Switzerland). Forward grouping was B RhD positive; however, the patient's serum showed pan-reactivity in reverse grouping [Figure 1]. Blood grouping was repeated using semiautomated technique (Diamed-ID typing) and conventional tube technique (CTT) with commercial antisera (Tulip Diagnostics, Goa, India). In-house-pooled (3 donors) red cells of A, B, and O group were used. Blood group and Rh typing was B RhD positive. Direct antiglobulin test of the patient was negative using monospecific Coombs gel card (DC-Screening II, Bio-Rad, Cressier, Switzerland). Red cell antibody screening was done in low-ionic-strength solution (LISS)/Coombs gel card (Bio-Rad, Cressier, Switzerland) using commercial three cell panel (ID-Diacell I-II-III, Bio-Rad, Cressier, Switzerland). It was pan-reactive (4+), autocontrol being negative. Antibody identification was done using commercial 11-cell panel (ID-Diapanel, Bio-Rad, Cressier, Switzerland) in LISS/Coombs gel card. It was pan-reactive (4+). Based on the above findings, the following differential diagnoses were considered: (a) an antibody to high-frequency antigen (HFA) and (b) antibodies to an antibiotic, which is one of the ingredients of the reagent red cells (in this case, cotrimoxazole in ID-Diacell). We did crossmatching with six group-specific packed red cells using LISS/Coombs gel card and CTT. All units were found compatible with the patient's serum [Figure 2]. Hence, an antibody to HFA was ruled out and antibodies to cotrimoxazole were likely. To confirm the same, the reagent red cells were washed 6 times using normal saline. Then, the grade of agglutination reduced from 4+ to 2+ and the effect could not be completely eliminated. Further, antibody screening was repeated with reagent red cells from another manufacturer (3% red cell suspension, Surgiscreen®, Ortho Clinical Diagnostics, USA) and in-house antibody screening cells (phenotyped for clinically significant antigens) which was negative. The antibiotics used in Surgiscreen were a combination of chloramphenicol, neomycin, and gentamicin. The serum was reactive with the reagent containing the drug in question and nonreactive with the reagent without the drug (in-house and another manufacturer). Overall findings were compatible with the cotrimoxazole-induced antibody. The patient denied any history of drug intake in the past. There was no feature of hemolysis.
|Figure 1: (a) Patient's serum shows 4+ reaction with commercial a b B-cells in reverse grouping done using fully automated blood grouping system (IH-500, Bio-Rad). (b) Patient's serum is nonreactive with in-house-pooled B-cells, when the blood grouping was repeated using semiautomated method|
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|Figure 2: (a) Serum was pan-reactive (4+) with commercial 11-cell panel used for red cell identification. (b) Cross-matches with 6 group-specific packed red cells were compatible|
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Antibody to a preservative component in a commercial red blood cell (RBC) reagent should be suspected when there patient's serum is pan-reactive with commercial screening or panel red cells but not with donor red cells at the same phase of testing. These antibodies react at both saline and Coombs phases of testing. Adenine, glucose, inosine, sodium citrate, and sodium chloride are among the preservatives commonly used in these reagents. The bacteriostatic agents included in these reagents are chloramphenicol, gentamycin, neomycin, vancomycin, paraben, sodium azide and steroids, a combination of trimethoprim and sulfamethoxazole (cotrimoxazole). Antibodies to these drugs interfering with immunohematology tests have been described earlier. Such interference has been documented with antibodies used in commercial antisera, red cells, and potentiators. The cotrimoxazole-induced antibody is a drug-dependent antibody, that is, the presence of the drug is needed to detect the drug-induced antibodies. Patients may have drug-induced antibodies in the serum. These antibodies cause false-positive reactions with commercial red cell panel, thereby complicating the compatibility testing. These reactions are mainly observed in vitro and are thought to carry no clinical significance. These drugs act mainly by binding to the red cell membrane (drug-membrane components). These drugs probably get anchored to a membrane glycoprotein. Pham et al. proposed that the drugs trimethoprim and sulfamethoxazole may attach to Kell glycoprotein and H substance, respectively. The bound drug then elicits drug-dependent and drug-independent reactions resulting in immune hemolysis. LISS also contains cotrimoxazole as a preservative. The addition of LISS alone could not result in agglutination of the donor red cells which could be explained by the following reasons: (1) the presence of drug-coated RBCs in the reagent. Six times washing of the reagent red cells was unsuccessful in the removing the drug and (2) also, the concentration of the drug in red cell reagent and LISS is unknown. In the present case, the patient denied any history of drug intake in the past. Drug-induced antibodies have been reported even in the sera of healthy donors and random patients. It is thought to be related to the prophylactic use of antimicrobial drugs in cattle feed. Longtime exposure to the drugs could also occur through contaminated water and air. Transfusion Medicine Department personnel should be aware of this rare phenomenon, especially when they use fully automated platform for blood grouping and “type and screen” policy for compatibility testing. Patch et al. recommended simple solutions (mainly CTT) to avert the unnecessary time delay in releasing the blood.
| Conclusion|| |
Antibiotics are included in the commercial reagents to inhibit bacterial growth. The presence of antibodies to these drugs in a patient's serum, even in healthy individuals, is not an uncommon phenomenon. Antibiotic-dependent antibody should be suspected when the serum is reactive with commercial red cells (containing the antibiotic) and not with the donor red cells (not containing the antibiotic). It is strongly emphasized to include CTT in such cases, facilitating timely provision of blood to these patients.
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Conflicts of interest
There are no conflicts of interest.
| References|| |
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[Figure 1], [Figure 2]