Approach to red blood cell antibody testing during pregnancy: Answers to commonly asked questions.

OBJECTIVE: To provide family physicians with an understanding of blood bank tests performed during pregnancy. The value of routine blood type and antibody tests, as well as the follow-up required when a patient develops a red blood cell antibody or experiences a fetal-maternal hemorrhage (FMH) will be reviewed. SOURCES OF INFORMATION: The approach described is based on the authors' clinical expertise and peer-reviewed literature from 1967 to 2020. MAIN MESSAGE: An ABO and RhD group and antibody screen test is performed on every pregnant patient during the first trimester. Although antibodies to red blood cell antigens occur infrequently, some can lead to substantial adverse fetal or neonatal consequences including hemolytic disease of the fetus and newborn. Early identification and quantification of important antibodies ensures that at-risk mothers are referred to and followed by obstetricians experienced with high-risk care. Another valuable and related test is the FMH test. For RhD-negative women, these tests are performed at every delivery and following antepartum events that could contribute to FMH. This test determines the number of fetal red blood cells in the maternal circulation and is used to determine the dose of Rh immune globulin an RhD-negative mother requires to prevent alloimmunization to fetal RhD. CONCLUSION: An understanding of blood bank tests performed during pregnancy and their role and limitations is vital to optimal practice and aids clinicians in their decision making. When there is doubt or confusion regarding antenatal testing or immunoprophylaxis, consult the regional laboratory or transfusion medicine specialists for additional guidance.

Evaluation of Automatic Blood Analyzer as Screening Method in Fetomaternal Hemorrhage.

Screening of fetomaternal hemorrhage (FMH) is essential in management of fetomaternal antigen incompatibilities of blood. The objective in this study was to evaluate the ability of automatic blood analyzer (ABA) to screen FMH, also comparing this method with flow cytometry (FCM). The contents of fetal red blood cells and fetal hemoglobin were evaluated by FCM and ABA, respectively, using both blood samples of male adults laced with umbilical cord blood diluted at 1/10, 1/100, 1/1,000, and 1/10,000, or blood from puerperal women collected within 48 hours following delivery. FCM had better performance (area under curve, AUC = 0.8723) than ABA (AUC = 0.6569) in detecting fetal blood laced with blood from male adults. At a critical level of 0.5%, ABA indicated that 27.5% of puerperal women would have FMH while FCM did not detect FMH. Our results showed that ABA overestimates FMH and disagrees with FCM on indicating puerperal women with FMH. ABA is inadequate for being used to screen for or to measure FMH.

"Provoked" feto-maternal hemorrhage may represent insensible cell exchange in pregnancies from 6 to 22 weeks gestational age.

OBJECTIVE: To quantify spontaneous and provoked fetal to maternal cell exchange in the first half of pregnancy. Transfer of fetal red blood cells (FRBCs) into the maternal circulation during the first half of pregnancy is poorly characterized but of clinical relevance for miscarriage management and invasive procedures. STUDY DESIGN: Prospective, descriptive cohort study of women presenting for surgical termination of pregnancy with sonographically confirmed gestational age (GA). Pre-procedural and post-procedural blood samples were collected to characterize both spontaneous (pre) and provoked (post) cell exchange with analysis via flow cytometry to quantify FRBC count. RESULTS: A total of 100 patients at 6-22 weeks GA contributed 200 matched pre- and post-procedural samples. FRBCs were identified in 69 patients including 4 who exhibited FRBCs pre-procedure only and 9 post-procedure only, for a total of 65 patients having post-procedural FRBCs. Of patients with FRBCs following their procedure, the majority (n=56, 86%) also exhibited evidence of cells before the procedure with just 9 patients (14%) exhibiting FRBCs only after. No dose-response relationship was appreciable between GA and FRBC count. CONCLUSION: After experiencing disruption of the placenta with instrumentation, roughly two thirds of patients had detectable FRBCs in maternal circulation following their procedure but-among those that did-the majority also exhibited cell presence prior to the procedure. This leads to further questions regarding the relationship between risk events and alloimmunization potential in previable pregnancies as the rate of spontaneous transplacental cell exchange may be underappreciated and the magnitude of provoked transfer may be overestimated. IMPLICATIONS: The relationship between feto-maternal hemorrhage risk events and alloimmunization potential in previable pregnancies has previously been poorly characterized but these data reveal spontaneous transplacental cell exchange may be underappreciated and the magnitude of provoked transfer may be overestimated.

ACOG Practice Bulletin No. 192 Summary: Management of Alloimmunization During Pregnancy.

When any fetal blood group factor inherited from the father is not possessed by the mother, antepartum or intrapartum fetal-maternal bleeding may stimulate an immune reaction in the mother. Maternal immune reactions also can occur from blood product transfusion. The formation of maternal antibodies, or "alloimmunization," may lead to various degrees of transplacental passage of these antibodies into the fetal circulation. Depending on the degree of antigenicity and the amount and type of antibodies involved, this transplacental passage may lead to hemolytic disease in the fetus and neonate. Undiagnosed and untreated, alloimmunization can lead to significant perinatal morbidity and mortality. Advances in Doppler ultrasonography have led to the development of noninvasive methods of management of alloimmunization in pregnant women. Together with more established protocols, Doppler ultrasound evaluation may allow for a more thorough and less invasive workup with fewer risks to the mother and fetus. Prevention of alloimmunization is addressed in another Practice Bulletin ().

ACOG Practice Bulletin No. 192: Management of Alloimmunization During Pregnancy.

When any fetal blood group factor inherited from the father is not possessed by the mother, antepartum or intrapartum fetal-maternal bleeding may stimulate an immune reaction in the mother. Maternal immune reactions also can occur from blood product transfusion. The formation of maternal antibodies, or "alloimmunization," may lead to various degrees of transplacental passage of these antibodies into the fetal circulation. Depending on the degree of antigenicity and the amount and type of antibodies involved, this transplacental passage may lead to hemolytic disease in the fetus and neonate. Undiagnosed and untreated, alloimmunization can lead to significant perinatal morbidity and mortality. Advances in Doppler ultrasonography have led to the development of noninvasive methods of management of alloimmunization in pregnant women. Together with more established protocols, Doppler ultrasound evaluation may allow for a more thorough and less invasive workup with fewer risks to the mother and fetus. Prevention of alloimmunization is addressed in another Practice Bulletin ().

Modification of host dendritic cells by microchimerism-derived extracellular vesicles generates split tolerance.

Maternal microchimerism (MMc) has been associated with development of allospecific transplant tolerance, antitumor immunity, and cross-generational reproductive fitness, but its mode of action is unknown. We found in a murine model that MMc caused exposure to the noninherited maternal antigens in all offspring, but in some, MMc magnitude was enough to cause membrane alloantigen acquisition (mAAQ; "cross-dressing") of host dendritic cells (DCs). Extracellular vesicle (EV)-enriched serum fractions from mAAQ+, but not from non-mAAQ, mice reproduced the DC cross-dressing phenomenon in vitro. In vivo, mAAQ was associated with increased expression of immune modulators PD-L1 (programmed death-ligand 1) and CD86 by myeloid DCs (mDCs) and decreased presentation of allopeptide+self-MHC complexes, along with increased PD-L1, on plasmacytoid DCs (pDCs). Remarkably, both serum EV-enriched fractions and membrane microdomains containing the acquired MHC alloantigens included CD86, but completely excluded PD-L1. In contrast, EV-enriched fractions and microdomains containing allopeptide+self-MHC did not exclude PD-L1. Adoptive transfer of allospecific transgenic CD4 T cells revealed a "split tolerance" status in mAAQ+ mice: T cells recognizing intact acquired MHC alloantigens proliferated, whereas those responding to allopeptide+self-MHC did not. Using isolated pDCs and mDCs for in vitro culture with allopeptide+self-MHC-specific CD4 T cells, we could replicate their normal activation in non-mAAQ mice, and PD-L1-dependent anergy in mAAQ+ hosts. We propose that EVs provide a physiologic link between microchimerism and split tolerance, with implications for tumor immunity, transplantation, autoimmunity, and reproductive success.

Understanding red blood cell alloimmunization triggers.

Blood group alloimmunization is "triggered" when a person lacking a particular antigen is exposed to this antigen during transfusion or pregnancy. Although exposure to an antigen is necessary for alloimmunization to occur, it is not alone sufficient. Blood group antigens are diverse in structure, function, and immunogenicity. In addition to red blood cells (RBCs), a recipient of an RBC transfusion is exposed to donor plasma, white blood cells, and platelets; the potential contribution of these elements to RBC alloimmunization remains unclear. Much attention in recent years has been placed on recipient factors that influence RBC alloantibody responses. Danger signals, identified in murine and human studies alike as being risk factors for alloimmunization, may be quite diverse in nature. In addition to exogenous or condition-associated inflammation, autoimmunity is also a risk factor for alloantibody formation. Triggers for alloimmunization in pregnancy are not well-understood beyond the presence of a fetal/maternal bleed. Studies using animal models of pregnancy-induced RBC alloimmunization may provide insight in this regard. A better understanding of alloimmunization triggers and signatures of "responders" and "nonresponders" is needed for prevention strategies to be optimized. A common goal of such strategies is increased transfusion safety and improved pregnancy outcomes.

Fetal-Maternal Hemorrhage Detected by Sudden Disappearance of Rh Immune Globulin-Related Anti-D.

BACKGROUND: Fetal-maternal hemorrhage is usually spontaneous and goes undetected but can be associated with adverse perinatal outcomes. CASE: We describe the detection of a fetal-maternal hemorrhage by abrupt disappearance of prophylactic anti-D on antibody screen in an Rh-negative mother with dichorionic twins admitted for atrial flutter of one twin. Both rosette and Kleihauer-Betke tests were positive. The diagnosis was confirmed by anemia in one twin at birth. CONCLUSION: Fetal-maternal hemorrhage requires a high index of suspicion for diagnosis. An unexpected sudden decline in Rh immune globulin-related anti-D may be an indication of fetal-maternal hemorrhage.

Anti-D alloimmunisation in pregnant women with DEL phenotype in China.

OBJECTIVES: To analyse anti-D alloimmunisation in pregnant women with D-elute (DEL) phenotype in China, for developing a predictive model to evaluate whether a person with the DEL phenotype can receive RhD-positive blood. BACKGROUND: Alloanti-D acquired by pregnancy or transfusion is one of the major causes of both haemolytic disease among newborns and haemolytic transfusion reactions. To date, there is little data available about the antigenic properties and immunogenicity of extremely weak D variants known as DEL. METHODS: RHD genotyping and D epitope mapping were performed using gene sequencing and comprehensive immunohaematological methods, respectively. DEL pregnant women carrying an RhD-positive fetus were tested for the presence of alloanti-D. RESULTS: A total of 130 of 142 (91·5%) pregnant women with a DEL phenotype were confirmed to carry the RHD (K409K) allele. Among 12 DEL women who appeared to have RHD-CE-D hybrid alleles, there were 1 RHD-CE (4-7)-D, 7 RHD-CE(4-9)-D, and 4 RHD-CE (2-5)-D alleles. Alloanti-D antibodies were detected in 6 of 142 DEL women, and all the six women had the partial DEL phenotype. CONCLUSION: The data indicate that partial DEL women appear at risk of alloimmunization to the D antigen. RhD immune globulin prophylaxis is necessary for partial DEL women. Partial DEL patients should receive only RhD-negative RBCs, whereas DEL patients with complete expression of antigen can safely receive RhD-positive RBCs.

Two cases of asymptomatic massive fetomaternal hemorrhage.

Evaluation of fetomaternal hemorrhage (FMH) in the immediate postpartum period is critical for the timely administration of Rh immunoglobulin (RhIG) prophylaxis to minimize the risk of alloimmunization in D-negative mothers of D-positive newborns. We report a series of two clinically-unsuspected cases of massive FMHs identified at our university medical center. Retrospective records of two cases of massive FMH were investigated using the electronic medical record. After positive fetal bleed screens, flow cytometric analysis for hemoglobin F was performed to quantify the volume of the hemorrhages in both cases. Flow cytometric enumeration with anti-D was also performed in one case. The two patients had 209.5 and 75 mL of fetal blood in circulation, resulting in 8 and 4 doses of RhIG administered, respectively. For the former patient, flow cytometric analysis with anti-D ruled out hereditary persistence of fetal hemoglobin and supported the fetal origin of the red cells. Due to the clinically-silent nature of both hemorrhages, further evaluation of the newborns' blood was not performed. These cases highlight the importance of rapidly obtaining accurate measurements of fetal blood loss via flow cytometric analysis in cases of FMH, particularly in clinically-unsuspected cases, to ensure timely administration of adequate immunoprophylaxis to D-negative mothers.

Prevalence of maternal red cell alloimmunisation: a population study from Queensland, Australia.

The aim of this study was to determine the current prevalence of red cell antigen alloimmunisation in Australia. Blood group (ABO and RhD) and red cell antibody screen results of pregnant women who presented at public hospitals in Queensland between the period of January 2011 and June 2013 were evaluated retrospectively. Antibody prevalence in pregnancy was compared to other published studies. A total of 482 positive antibody screens from 66,354 samples (0.73%) were identified. The prevalence of antibodies was: anti-E 27.6%; anti-D 10.4%; anti-Kell 9.5%; anti-c 8.7%; anti-Duffy 3.1%, including Fy and Fy; anti-MNS 7.9%, including M, N, S and s; anti-Lewis 6%, including Le and Le; and multiple antibodies (16%, including anti-D). Compared to other studies, including one from Australia in 1977, the anti-D alloimmunisation rate had dropped significantly, with little change in anti-c and some increase in anti-E and anti-Kell cases. Continued vigilance is required to ensure eligible RhD negative women receive prophylaxis according to the current RhD immunoprophylaxis guidelines, especially those who have a fetomaternal haemorrhage (FMH). RhD positive women that are at risk of developing an antibody during pregnancy should have their pregnancy monitored according to published guidelines. Once antibodies are identified, consideration should be given to paternal antigen status in an attempt to identify the pregnancy that will be at risk of alloimmunisation.

Assessment of feto-maternal hemorrhage among rhesus D negative pregnant mothers using the kleihauer-betke test (KBT) and flow cytometry (FCM) in Addis Ababa, Ethiopia.

BACKGROUND: This study aimed to assess fetomaternal hemorrhage (FMH) among RhD negative pregnant mothers using two techniques, Kleihauer-Betke (KBT) and Flow cytometry (FCM). To determine if patient-specific doses of prophylactic anti-D warrant further investigation in Ethiopia and wider Africa. METHODS: Hospital- based cross-sectional study was conducted among 75 RhD negative pregnant mothers using convenient sampling technique. RESULT: FMH has been detected in 52% and 60% by KBT and FCM techniques, respectively. The volume of FMH quantified in the majority of the cases (92.5% and 87%) was <10 mL fetal blood while >30 mL in 1.3% (1/75) and 2.7% (2/75) as calculated by KBT and FCM, respectively. The FMH calculated by the two methods have good correlation; r = 0.828 (p = 0.000) for categorized and r = 0.897 (p = 0.000) for continuous values and the agreement between the FCM and KBT was moderate with kappa (κ) value of 0.53 (p = 0.000). CONCLUSION: Most of FMH calculated (<10 mL) could have been neutralized by lower doses which might have lower costs than administering 300 µg dose which is currently in practice in our country for affording mothers. Besides, it also showed that the volume of FMH was >30 mL in 1.3% and 2.7% of the cases as calculated by KBT and FCM, respectively, which need more than 300 µg dose RhIG for neutralization. Further investigation into the cost- effectiveness and scalability of patient- specific dosing of prophylactic anti-D appears warranted.

Screening for HLA antibodies in plateletpheresis donors with a history of transfusion or pregnancy.

BACKGROUND: Transfusion-related acute lung injury (TRALI) is known as a life-threatening complication of transfusion. HLA and HNA antibodies have been associated with the immune pathway of TRALI. Since donors with a history of transfusion and/or pregnancy are presumed to have an increased risk of carrying such antibodies, we investigated the association of a history of transfusion or pregnancy with the occurrence of HLA alloimmunization in our donor population. STUDY DESIGN AND METHODS: A total of 1018 female plateletpheresis donors and male plateletpheresis donors with a history of transfusion were enrolled in the study. Included donors were systematically screened, using Luminex technology, for anti-HLA Class I and II. The association of donor history with HLA alloimmunization status was analyzed. RESULTS: The overall alloimmunization rate was 20.2%. In 0.0% of the nulliparous transfused female donors and in 1.3% of the transfused male donors, anti-HLA were detected. Thirty-one percent of the parous women versus 4.2% of the nulliparous women screened positive for anti-HLA. The rate of HLA alloimmunization increased with parity. CONCLUSION: Our data indicate that a history of transfusion is a minor risk factor for immunization against HLA antigens. In contrast, former pregnancies constitute a major risk factor for the development of HLA antibodies. Since HLA alloimmunization rate increases with parity, TRALI risk reduction measures should focus on this particular donor population. Repeated testing of female plateletpheresis donors after each pregnancy is implemented in our blood service.

[Guideline for prevention of RhD alloimmunizationin RhD negative women]. / Doporucení k provádení prevence RhD aloimunizace u RhD negativních zen.

Events following which immunoglobulin (Ig) G anti-D should be given to all RhD negative women with no anti-D alloantibodies: First trimester indications (IgG anti-D sufficient dose of 50 µg*) - termination of pregnancy, spontaneous abortion followed by instrumentation, ectopic pregnancy, chorionic villus sampling, partial molar pregnancy; Second and third trimester indications (IgG anti-D sufficient dose of 100 µg*) - amniocentesis, cordocentesis, other invasive prenatal diagnostic or therapeutic procedures, spontaneous or induced abortion, intrauterine fetal death, attempt at external cephalic version of a breech presentation, abdominal trauma, obstetric hemorrhage; Antenatal prophylaxis at 28th weeks of gestation (IgG anti-D sufficient dose of 250 µg*); Delivery of an RhD positive infant** (IgG anti-D sufficient dose of 100 µg*); Minimal dose*: before 20 weeks gestation - 50 µg (250 IU), after 20 weeks gestation*** - 100 µg (500 IU); Timing: as soon as possible, but no later than 72 hours after the event. In cases where prevention of RhD alloimmunization is not performed within 72 hours of a potentially sensitising event, it is still reasonable to administer IgG anti-D within 13 days, and in special cases, administration is still recommended up to a maximum interval of 28 days postpartum; Legend: *administration of a higher dose of IgG anti-D is not a mistake, ** also if the D type is not known, *** simultaneous assessment of the volume of fetomaternal hemorrhage (FMH) to specify the dose is suitable; The FMH volume assessment - If the volume of fetal erythrocytes (red bood cells, RBCs) which entered maternal circulation is assessed, intramuscular administration of IgG anti-D in a dose of 10 µg per 0.5 mL of fetal RBCs or 1 mL of whole fetal blood is indicated. IgG anti-D in a dose of 10 µg administered intramuscularly should cover 0.5 mL of fetal RhD positive RBCs or 1mL of whole fetal blood. FMH is the fetal RBC volume; fetal blood volume is double (expected fetal hematocrit is 50%).

Usefulness of maternal anti-HPA-1a antibody quantitation in predicting severity of foetomaternal alloimmune thrombocytopenia.

OBJECTIVE: To study the clinical usefulness of maternal anti-HPA-1a antibody levels in predicting severe foetomaternal alloimmune thrombocytopenia (FMAIT). BACKGROUND: Recent studies using an international anti-HPA-1a standard have shown a correlation between maternal antibody levels and neonatal thrombocytopenia. Cut-off values for identifying high-risk pregnancies have also been suggested. MATERIALS: In 1986-2010, HPA-1a alloimmunisation was confirmed in 84 women with 129 pregnancies. Maternal samples were obtained at delivery and during subsequent pregnancies. Anti-HPA-1a was quantified using a MAIPA assay with a detection limit of 0·8 IU mL(-1) (WHO reference serum 03/152). Antibody levels were compared with the severity of neonatal disease in the index and in the subsequent pregnancies. RESULTS: In the index cases, the correlation between an anti-HPA-1a level and neonatal platelet count did not reach statistical significance (n = 77, P = 0·074). However, the platelet counts and antibody levels in cases with cutaneous (n = 45) or intracranial haemorrhage (n = 7) were significantly different from cases with no evidence of bleeding (n = 20). In the subsequent pregnancies, there was a stronger association between the second trimester anti-HPA-1a level and the foetal platelet count (n = 16, P = 0·046). The positive predictive value of the maternal antibody level for a foetal platelet count <20 × 10(9) L(-1) was 90%, but the negative predictive value only 31%. CONCLUSION: Although a higher anti-HPA-1a level correlated with a more severe neonatal disease, barely detectable antibody levels were also observed in severely affected pregnancies. Cut-off values with sufficient sensitivity and specificity to identify these foetuses could not be found. A previous obstetric history still remains the most useful predictive parameter for severe FMAIT in clinical practice.

Maternal red blood cell alloimmunisation in south western Uganda.

AIMS/OBJECTIVES: To identify the frequency and nature of maternal red blood cell (RBC) alloimmunisation in Uganda and to determine the prevalence of RhD negativity and the rate of RBC alloimmunisation in Ugandan pregnant women. BACKGROUND: Haemolytic disease of the foetus and newborn (HDFN) results from maternal alloimmunisation following exposure to allogeneic RBCs during pregnancy or blood transfusion. The prevalence of maternal RBC alloimmunisation in Ugandans is not known. MATERIALS AND METHODS: Pregnant women at Mbarara Hospital, South Western Uganda, were investigated in a cross-sectional study. Demographics, transfusion and obstetric histories were recorded. Maternal RBC alloimmunisation was demonstrated using immunohaematological techniques. RESULTS: A total of 2001 pregnant women were recruited; 3.6% of them being RhD negative. Forty-five women (2.2%; 95% CI: 1.6-2.9) were found to be alloimmunised to RBC antigens. There were 38 RBC alloantibodies of known specificity including anti-S, 12; anti-M, 11; anti-Le(a) , 6; anti-D, 4 and 1 each of anti-K, anti-Fy(b) , anti-Jk(a) , anti-Lu(a) and anti-Kp(a) . In two women (4.4%), there were antibody combinations (anti-M+S and anti-K+Kp(a) ). Obstetric history, gestational age and previous immunising events were not significantly associated with the rate of alloimmunisation. CONCLUSIONS: This study revealed a maternal RBC alloimmunisation rate of 2.2% which was comparable with findings from a Zimbabwean study where the prevalence was 1.7%. Given the 6·0% prevalence of anti-D among RhD-negative women in our study and the high immunogenicity of the D antigen, programmes for preventing anti-D alloimmunisation and HDFN in Uganda should be considered seriously.

[Management of feto-maternal red cell allo-immunizations]. / Prise en charge des allo-immunisations fœto-maternelles antiérythrocytaires.

Feto-maternal red cell alloimmunization is defined by the presence in a pregnant woman of alloantibodies directed against blood group antigens present on the red blood cells of the fetus and inherited from the father. It arises from the immune response to a first contact to these same antigens during a prior transfusion, transplant or pregnancy. The placental transfer and the fixation of the antibodies on the fetal red cells antigenic targets lead to a haemolysis in the fetus and the newborn. The resulting haemolytic disease can show different clinical forms, from a mild anaemia with neonatal hyperbilirubinemia to a major fetal damage with stillbirth caused by hydrops fetalis. The objective of management strategies of feto-maternal alloimmunization is to detect and monitor maternal alloimmunization and to appreciate the effects on the fetus or the newborn. Since a few years, some new non-invasive techniques of surveillance are used, for instance fetal RHD genotyping on maternal plasma and evaluation of fetal anaemia through velocimetry measurement of the blood flow in the middle cerebral artery. The need for a careful postnatal surveillance has to be emphasized due to the neonatal anaemia, which can be prolonged, and to the resurgence of cases of severe neonatal icteruses recently reported by the Académie de Médecine. The policy of prevention of anti-RH1 alloimmunization should also benefit from the evolution of biological techniques by allowing an improved targeting of concerned women.

Clinical and laboratory aspects of Ro/SSA-52 autoantibodies.

Anti-Ro/SSA antibodies, which were described for the first time in systemic lupus erythematosus (SLE) and Sjögren's syndrome (SS), are the most prevalent extractable nuclear antigen (ENA) specificity identified in laboratories. Two types of anti-Ro/SSA antibodies have been described, anti-SSA-52 kDa (aSSA52) and anti-SSA-60 kDa (aSSA60), each specific to different antigens. Anti-Ro/SSA52 autoantibodies are more frequent than other autoantibodies possibly because of the antigen's accessible and ubiquitous nature. The sites involved and the symptoms associated with these autoantibodies depend on the antigen's structural variability. Isolated congenital complete atrioventricular block (CAVB) shows a close association with maternal anti-Ro/SSA and anti-La/SSB antibodies; the highest relative risks of CAVB are seen in offspring of mothers with antibodies against 52-kDa Ro and 48-kDa La proteins. Anti-Ro/SSA52 antibodies have little impact on adult rheumatic autoimmune diseases or adult cardiac arrhythmias, but the course of autoimmune liver diseases is greatly worsened by their presence, and solid tumours tend to relapse. Their diagnostic role in rheumatic diseases is controversial, although a significant association between isolated anti-Ro/SSA52-kDa positivity and myositis and to a lesser extent with systemic sclerosis (SSc) has been described. However, the majority of the specific diagnosis is mostly based on the simultaneous presence of other autoantibodies that seems diagnostically more relevant.