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Year : 2020  |  Volume : 11  |  Issue : 4  |  Page : 199-203

Detection of anti-f on a 51-year-old Saudi female

Department of Pathology and Laboratory Medicine, King Abdullah Specialist Children Hospital KASCH, King Abdulaziz Medical City, CR - Ministry of National Guard Riyadh, Saudi Arabia

Date of Submission06-May-2020
Date of Decision26-May-2020
Date of Acceptance01-Aug-2020
Date of Web Publication17-Nov-2020

Correspondence Address:
Mr. Ahmed Alharbi
Department of Pathology and Laboratory Medicine, King Abdullah Specialist Children Hospital, King Abdulaziz Medical City, Riyadh
Saudi Arabia
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/joah.joah_59_20

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Anti-f/ce is a rare antibody but nevertheless associated with Hemolytic Disease of the Fetus and Newborn (HDFN) and Hemolytic Transfusion Reactions (HTR). This antibody shows reaction against products of the seemingly common R0 or r haplotypes. Often detected with other Rh antibodies, these reactions are enhanced against cells pretreated with common protease enzymes. The findings concluded the presence of anti-f/ce using routine procedures. Although seemingly innocuous being 'enzyme only', cases as these must be dealt with proper discernment to avoid risks of HTR and HDFN. The purpose of this article is to report the detection of an anti-f on a 51-year-old female with unknown transfusion history by a routine blood bank and to show how these infrequent antibodies are being misdiagnosed which could be avoided.

Keywords: Antibodies detected by enzyme only, anti-f/ce, f antigen, nonspecific antibody

How to cite this article:
Alharbi A, Batarfi K, Kiseo PD, Saleh JF, Shareefi AA, Nourah AH. Detection of anti-f on a 51-year-old Saudi female. J Appl Hematol 2020;11:199-203

How to cite this URL:
Alharbi A, Batarfi K, Kiseo PD, Saleh JF, Shareefi AA, Nourah AH. Detection of anti-f on a 51-year-old Saudi female. J Appl Hematol [serial online] 2020 [cited 2021 Apr 11];11:199-203. Available from: https://www.jahjournal.org/text.asp?2020/11/4/199/300770

  Introduction Top

Of the 34 human blood group systems, the Rh system elicits the most complexity with as much as 61 antigens known to date. Most of the Rh incompatibilities have been associated with the five major antigens (D, C, c, E, and e). The Rh system also comprises some compound antigens. Conformational changes as a result of amino acids associated with the RHCE create epitopes that define these compound antigens. Formerly postulated as “cis products” to indicate that these were due to antigens being expressed on the same haplotype, however, it has already been recognized nowadays that these antigens are expressed on a single protein.[1] In this article, we report a case of a rare alloantibody against a product of a compound Rh antigen. Anti-f was detected and identified by routine blood bank procedures from a patient who came to the hospital for a general checkup.

  Case Report Top

A 51-year-old Saudi female was seen at the outpatient clinic for shortness of breath, productive cough, and shoulder pain. The patient was diagnosed with Leiomyosarcoma with lung mediastinal involvement. She was recently admitted at an outside hospital for fainting, which was attributed to the newly discovered metastasis to the brain. Information about the patient's transfusions history at outside hospitals/institutions was unknown.

According to our Blood Bank Laboratory Information System, the patient is known to be O positive and antibody screen negative, which she was tested 8 months prior. On that same admission 8 months ago, the patient received 2 adult doses of platelet concentrates (12 units) due to low platelet count (6.0, normal range: 150–400 × 109/L) as well as 2 units of packed red blood cells (RBCs) for low hemoglobin level (80, normal range: 120–160 g/L). After discharge, she had multiple appointments for chemotherapy sessions and palliative care clinic visits where transfusion was not requested. On this admission, however a routine type and screen was ordered for the patient. Since the current hemoglobin was acceptable, no blood products were requested.

Materials and methods

Type and screen policy

The AABB recommends that compatibility tests must be performed on samples collected within 72 h of RBC transfusions when the patient has been pregnant or transfused within the preceding 3 months or if the history is uncertain or unavailable.[1] Since the blood bank is AABB accredited, it has implemented a strict 72-h type and screen validity before the preparation of any RBC products.

Serologic testing

Whole blood samples were collected via venipuncture into an EDTA tube (BD Vacutainer K2E EDTA, 6 mL, 10.8 mg). Samples were then centrifuged at 4800 rpm for 10 min to separate plasma from the RBCs, which can be then stored at 1°C–10°C for 14 days as per AABB guidelines.[1] ABO/Rh grouping and Rh antigen phenotyping were done by the automation system on the Galileo Neo® system (Immucor Inc., Norcross, GA, USA).

The antibody screens and the initial antibody identification were processed following the manufacturer's instructions of the Capture-c® Ready-Screen® and Capture-R® Ready-ID® (Immucor Inc., Norcross, GA, USA) accordingly. Both tests were done on the same automation equipment as the ABO/Rh.

The patient's samples were tested as above, and in addition, the direct antiglobulin test (DAT) was performed on the Capture-R® Select® Technology (Immucor Inc., Norcross, GA, USA) on the same automation technique as ABO/Rh typings as well.

The secondary antibody identification panel was performed via gel centrifugation technique. The technique used the patient's plasma which was tested against 11 untreated and 11 enzyme pretreated cells on anti-IgG (untreated) and neutral (enzyme pretreated) cassettes (Across® Identicell Panel®, DiaPro®). After incubation at 37°C for 15 min, the cassettes were then centrifuged at 128 g for 9 min, which were then subsequently interpreted macroscopically.

  Results Top

One EDTA sample was received as a routine type and screen. Initial results came as O Rh positive and antibody screen positive. The antibody screen was positive (reaction grade 2, scale 0–4) on one out of three screening cells [Figure 1].
Figure 1: Antibody screening panel (Capture-R® Ready-Screen®, Immucor Inc.)

Click here to view

As soon as the antibody screening detected as positive, the antibody identification protocol was followed. The initial identification panel was done via the same technique as the antibody screen where the reaction pattern did not indicate a definite specificity [Figure 2]. Although initially nonspecific, reaction to cells possessing at least one r (dce) haplotype was noted. The technologist raised the hypothesis of the presence of an antibody against the r (dce) haplotype. The direct antiglobulin testing was subsequently done, to which then came out negative(not shown).
Figure 2: Antibody identification panel (Capture-R® Ready-ID®, Immucor Inc.)

Click here to view

The patient's RBCs were also tested for Rh antigens since it was assumed that the patient did not receive any RBC transfusion within the past 3–4 months. Herein, it was determined that the patient's most probable Rh phenotype was R1R1. To complete the workup, an additional sample was then requested. The subsequent sample had the same antibody screen reaction as the initial [Figure 1]; therefore, the second antibody identification panel was done by gel card technique with untreated panel cells and panel enzyme-pretreated (papain) cells, with the intention on proving the initial supposition. The gel card panel showed reactions consistently against cells containing R0 or r haplotypes despite being only detectable against enzyme pretreated cells [Figure 3] confirming the presence of the rare antibody: anti-f. Although, the f antigen determination was not done due to unavailability of the antisera.
Figure 3: Second antibody identification panel(Across® Identicell Panel®, DiaPro®)

Click here to view

Anti-f and f antigen

Anti-f was first described in 1953 from a 30-year-old multitransfused patient diagnosed with hemophilia. The patient had several antibodies against blood group antigens, one of which was referred to as a novel antibody.[2] Anti-ce (also known as anti-f) is reacting against the products of RHCE*ce which also shows reactions against d (C) ces cells, although it has been reported to react to products of some unusual RHCE haplotypes which is conflicting to predictions basing their results against both anti-c and anti-e. Several Dc − haplotypes, for example, show ce or f (RH6) antigen activity but not e. Anti-f is seldom found as lone specificity. It is commonly detected alongside other antibodies such as anti-c and anti-e. Reports of anti-f detected in blacks may apparently actually be anti-hrs (RH19). This antibody is also known to weaken in vivo and in vitro. While its significance in a transfusion reaction was not definite, one autoanti-f was detected in a DCe/dce patient which could only be detected after doing an acidified antiglobulin test.[3],[4] Since then, this rare antibody has been identified on multitransfused patients, one example of which is of a 66-year-old patient in South Korea diagnosed with pancreatic cancer.[5] A study in 2018 detected one anti-f specificity on 105 sickle cell disease patients receiving red cells from African-American donors Despite being RhD, RhCE and Kell (K1) antigens matched.[6] Anti-f has been implicated in at least one hemolytic transfusion reaction (HTR). In 1985, O'Reilly et al. reported a case of a delayed HTR on a 30-year-old Caucasian man probably caused by anti-f.[7] Aside from HTRs, this rare antibody has also been associated with a hemolytic disease of the fetus and newborn (HDFN).[8]

Antigen f is one of the products of compound antigens collectively known as “cis products,” which denote that these are due to antigens positioned on the same haplotype. This antigen (RH6, ISTB Designation) can be detected if c and e are on the same haplotype. Although formerly referred to as a compound antigen, the f antigen has already been determined to be a distinct immunogen which is a result of conformational changes in the RHCE protein though molecular requirements of its expression is not yet fully understood. When tested against the five main Rh antisera (anti-D, anti-C, anti-E, anti-c, and anti-e), Rzr (DCE/dce) could not be distinguished from R0r (DcE/DCe) by their antigen presentation, however, when tested with anti-f, reactions could only be observed on the latter.[4],[9]

Enzyme-only antibodies

There are some Rh antibodies that show activity only to protease enzyme-pretreated cells. These antibodies show no activity on usual antibody identification methods using enzyme untreated panel cell technique. While most of these antibodies show “naturally occurring” anti-E specificities, other “enzyme-only” reactions against antigens D, C, c, e, and ce (f) have already been reported.[3] Some studies may suggest that testing pretransfusion samples against enzyme-pretreated cells would deem the procedure pointless since most of these enzyme-only reacting antibodies play a minimal role in HTRs. However, there have been multiple examples of HTRs caused by “enzyme-only” anti-C, anti-E, anti-c, and anti-e+ce.[10],[11],[12]

  Discussion Top

This case involves a rare antibody that could be inadvertently misdiagnosed, though nevertheless potentially dangerous. The judgment of the staff to further the tests brought about the detection of this rare anti-f. Since anti-f or anti-ce has been implicated HTRs and at least one HDFN, careful discernment is required in handling these cases which, therefore, demands a certain level of knowledge and expertise.

This case reports a rare antibody against a product of a compound antigen. Although the f antigen determination was not possible due to antisera unavailability, the conviction of the team to the detection of anti-f was due to the consistency of the test results. The antibody detected started out as a seemingly innocuous reaction. Further examinations revealed an “enzyme-only” anti-f. Although generally clinically insignificant, even these “enzyme-only” specificities have also been shown to play a role in HTRs as well. After the detection of the antibody, the immunohematology team escalated the incident to the pathologist on duty. Four units of packed RBCs (R1R1 and R2R2) were cross-matched by the gel card method via IAT and all were found to be compatible. As per recommendations, it is generally safe to provide patients with anti-f red cells lacking either antigens c or e. Although, it has to be noted that some e antigen-negative haplotypes (i.e., Dc-) could still elicit the ce/f antigen.

  Conclusion Top

The detection and identification of uncommonly seen antibodies pose a challenge to some blood banks. To an undertrained eye, most of these rare antibodies would inadvertently fall into the “nonspecific reactions” or “antibodies of unknown specificity” category where the antibody reaction pattern is not matched with any antigen on the panel cell sheet. Therefore, a better understanding of the nature of these unusual antibodies would give benefit to the handling staff to give a safe blood transfusion to the patients. Nonspecific reaction category should be utilized with caution, for some of these might actually be of clinical significance antibody.

What was vital to the detection of this unusual antibody was the ample knowledge the handling staff possessed. To be able to handle these situations effectively at all times, elevating the expertise of the technical staff should be the aim of any laboratory. But how should it be done? The adage “Education is key” might be partially true in this event, but in a workplace with a diverse possibility of unusual cases, education alone will not suffice. Quality education and consistent quality re-education is the perfect blend to empower all technical personnel.

The authors suggest that each laboratory must have a sound training plan and competency checks in place to achieve better and quality results. In addition, Also, we recommend that these so-called “antibodies/reactions of unknown specificities” which are commonly reported should be investigated to avoid the routine generic use of “non-specific reaction . The authors propose further studies be initiated to identify the clinical significance of these phenomena, which may lead to a better understanding of the reactions and better clinical services to the patients rather being than reported as nonspecific reaction/s.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Fung MK, Grossman BJ, Hillyer CD, Westhoff CM. The RH system, AABB Technical Manual. 18th ed. Bethesda, Maryland, USA AABB Press; 2014. p. 317, 329.  Back to cited text no. 1
Rosenfield RE, Vogel P, Sanger R, Race RR. A new Rh antibody, anti-f. Br Med J 1953;1:975.  Back to cited text no. 2
Daniels G. Rh and RHAG Blood Group Systems, Human Blood Groups. 3rd ed. Chichester, U.K: Wiley-Blackwell; 2013. p. 211, 231.  Back to cited text no. 3
Reid ME, Lomas-Francis C. The RH Blood Group System, The Blood Group Antigen Factsbook. 2nd ed. New York, U.S.A: Elsevier Academic Press; 2004. p. 140.  Back to cited text no. 4
Nah H, Shin S, Kim S, Lee E, Kim HO. A case report of anti-f(ce) identified in a patient with pancreatic cancer. The Korean Society of Blood Transfusion. Korean J Blood Transfusion 2016;27:174-82.  Back to cited text no. 5
Chou ST, Vege PS, Coleman SL, Friedman DF, Keller M, Westhoff CM. RH genotype matching for transfusion support in sickle cell disease. Blood 2018;132:1198-207.  Back to cited text no. 6
O'Reilly RA, Lombard CM, Azzi RL. Delayed hemolytic transfusion reaction associated with Rh antibody anti-f:First reported case. Vox Sanguinis 1985;49:336-9.  Back to cited text no. 7
Spielmann W, Seidl S, von Pawel J. Anti-ce (anti-f) in a CDe/cD- mother, as a cause of haemolytic disease of the newborn. Vox Sanguinis 1974;27:473-7.  Back to cited text no. 8
Harmening DM. The RH Blood Group System, Modern Bloodbanking and Transfusion Practices. 7th ed. Philadephia, U.S.A: F.A Davis Company; 2019. p. 185.  Back to cited text no. 9
Enko D, Habres C, Wallner F, Mayr B, Halwachs-Baumann G. Frequencies and specificities of “enzyme-only” detected erythrocyte alloantibodies in patients hospitalized in Austria: Is an enzyme test required for routine red blood cell antibody screening? J Blood Transfus 2014;532919.10.1155/2014/532919.  Back to cited text no. 10
Issitt PD, Combs MR, Bredehoeft SJ, Campbell ML, Heimer M, Joyner L, et al. Lack of clinical significance of “enzyme-only” red cell alloantibodies . Transfusion 1993;33:284-93.  Back to cited text no. 11
Judd WJ, Davenport RD, Suchi M. An 'enzyme-only' IgG C3-binding alloanti-C causing an acute hemolytic transfusion reaction. Transfusion 2000;40:119s.  Back to cited text no. 12


  [Figure 1], [Figure 2], [Figure 3]


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