Evaluation of five commercial tests for detection of immunoglobulin M antibodies to human parvovirus B19

Parvovirus b19 infection in pregnancy - A review

Parvovirus B19 (B19V) is a widespread infection that may affect 1-5% of pregnant women, mainly with normal pregnancy outcome. Vertical transmission occurs in 33-51% of cases of maternal infection. B19V infection is an important cause of fetal morbidity (fetal anaemia and non-immune hydrops) and mortality, predominantly in the second trimester. Diagnosis of B19V infection requires a multi-method approach using mainly serology and PCR techniques. Severe fetal anaemia is managed with intrauterine transfusion with perinatal survival rates following intrauterine transfusion ranging from 67% to 85%. If fetal anaemia is mild, and considering that hydrops can spontaneously resolve, invasive therapy is not recommended and B19V complicated pregnancy may be non-invasively monitored by serial ultrasound examination and MCV-PSV measurements. As an alternative, intrauterine IVIG therapy has been described with successful treatment of fetal hydrops. No specific antiviral therapy or vaccine is presently available for B19V infection but efforts in the search for compounds inhibiting B19V replication are now being pursued. New virus-like-particle based parvovirus B19 vaccine candidates, produced by co-expressing VP2 and either wild-type VP1 or phospholipase-negative VP1 in a regulated ratio from a single plasmid inSaccharomyces cerevisiae have been developed and show sufficient promise to test in humans.

Comparison of 4 commercial enzyme immunoassays for serology testing of human parvovirus B19 infection

BACKGROUND

Parvovirus B19 is a pathogenic virus often diagnosed by serology, yet little is known about analytical performance of commercial enzyme immunoassays (EIAs).

OBJECTIVE

To investigate performance of 4 EIAs for parvovirus B19 IgM and IgG: Liaison, Euroimmun, Mikrogen and Virion/Serion.

STUDY DESIGN

To compare 4 EIAs to Biotrin's ELISA on 168 samples and determine consensus score for discordant samples using Mikrogen's confirmatory line assay.

RESULTS

Two thirds of results for IgM/IgG were identical for all 4 EIAs and Biotrin. Liaison shows the highest IgM sensitivity, but has low specificity. Euroimmun lacks IgM sensitivity. Mikrogen had a good overall performance, but had the lowest IgG specificity. Virion/Serion had variable performance with a low IgM specificity and the most borderline and cross-reactive results.

CONCLUSIONS

Liaison and Mikrogen have similar performance to Biotrin's ELISA. Euroimmun lacks sensitivity and Virion/Serion produced many borderline and cross-reactive results.

Human Parvoviruses

Parvovirus B19 (B19V) and human bocavirus 1 (HBoV1), members of the large Parvoviridae family, are human pathogens responsible for a variety of diseases. For B19V in particular, host features determine disease manifestations. These viruses are prevalent worldwide and are culturable in vitro, and serological and molecular assays are available but require careful interpretation of results. Additional human parvoviruses, including HBoV2 to -4, human parvovirus 4 (PARV4), and human bufavirus (BuV) are also reviewed. The full spectrum of parvovirus disease in humans has yet to be established. Candidate recombinant B19V vaccines have been developed but may not be commercially feasible. We review relevant features of the molecular and cellular biology of these viruses, and the human immune response that they elicit, which have allowed a deep understanding of pathophysiology.

Effects of Parvovirus B19 Infection in Renal Transplant Recipients: A Retrospective Review of Three Cases

Parvovirus B19 (PVB19) is a DNA virus which causes clinically relevant infection in renal transplant recipients (RTR) leading to significant morbidity. Manifestations include erythropoietin resistant anemia, proteinuria, and glomerulosclerosis in the allograft. Severe infection may require administration of intravenous immunoglobulin, reduction in immunosuppression and transfusions. The major challenge in managing and preventing the infection in RTR involves the act of balancing the decreased level of immunosuppression and the risk of rejection. The objective of this article is to understand the importance of PVB19 infection and its outcome in RTR. We reviewed the medical records of three RTR with confirmed PVB19 infection and recorded patient information including demographics, clinical and laboratory data, management, and outcome. The average time of occurrence of PVB19 infection as transplant was 8.6 weeks and they presented with symptomatic anemia. Elevated creatinine values were noted in two of them. Following treatment, anemia improved and creatinine values returned to baseline. One of them developed an early relapse and had to be treated once again similarly. We emphasize the importance of maintaining a high index of suspicion for PVB19 infection in patients with anemia in the posttransplant phase, especially in patients on higher doses of immunosuppressants. Early and proper treatment can prevent worsening clinical condition and possible effects on the allograft.

Parvovirus B19 infection in the first trimester of pregnancy and risk of fetal loss: a population-based case-control study

Because parvovirus B19 infection during pregnancy has been associated with increased risk of fetal loss in small or selected study populations, the authors evaluated the risk in a population-based study. A nested case-control study was conducted by using a population-based screening for syphilis in 3 regions in Denmark from 1992 to 1994. Cases of women with fetal loss were identified in the National Patient Register (n = 2,918), and control women with live-born children were identified in the Medical Birth Register (n = 8,429) by matching on age and sampling week. First-trimester serum samples were tested for parvovirus B19 immunoglobulin M positivity. Parvovirus B19 immunoglobulin M positivity was associated with a 71% increased risk of fetal loss (odds ratio = 1.71, 95% confidence interval: 1.02, 2.86). Adjustment for number of children or stratifying for gestational age at loss did not change the risk estimate. Assuming causality, only 0.1% of fetal losses were attributable to parvovirus B19 positivity, a proportion which could increase to approximately 1% during epidemic periods. In conclusion, acute parvovirus B19 infection during the first trimester of pregnancy was associated with an increased risk of fetal loss. However, the impact on the overall burden of fetal losses appeared small even during epidemics.

Etiologies of rash and fever illnesses in Campinas, Brazil

BACKGROUND

Few population-based studies of infectious etiologies of fever-rash illnesses have been conducted. This study reports on enhanced febrile-rash illness surveillance in Campinas, Brazil, a setting of low measles and rubella virus transmission.

METHODS

Cases of febrile-rash illnesses in individuals aged <40 years that occurred during the period 1 May 2003-30 May 2004 were reported. Blood samples were collected for laboratory diagnostic confirmation, which included testing for adenovirus, dengue virus, Epstein-Barr virus (EBV), enterovirus, human herpes virus 6 (HHV6), measles virus, parvovirus-B19, Rickettsia rickettsii, rubella virus, and group A streptococci (GAS) infections. Notification rates were compared with the prestudy period.

RESULTS

A total of 1248 cases were notified, of which 519 (42%) had laboratory diagnosis. Of these, HHV-6 (312 cases), EBV (66 cases), parvovirus (30 cases), rubella virus (30 cases), and GAS (30 cases) were the most frequent causes of infection. Only 10 rubella cases met the rubella clinical case definition currently in use. Notification rates were higher during the study than in the prestudy period (181 vs 52.3 cases per 100,000 population aged <40 years).

CONCLUSIONS

Stimulating a passive surveillance system enhanced its sensitivity and resulted in additional rubella cases detected. In settings with rubella elimination goals, rubella testing may be considered for all cases of febrile-rash illness, regardless of suspected clinical diagnosis.

Parvovirus B19 infection in human pregnancy

Human parvovirus B19 infection is widespread. Approximately 30-50% of pregnant women are nonimmune, and vertical transmission is common following maternal infection in pregnancy. Fetal infection may be associated with a normal outcome, but fetal death may also occur without ultrasound evidence of infectious sequelae. B19 infection should be considered in any case of nonimmune hydrops. Diagnosis is mainly through serology and polymerase chain reaction. Surveillance requires sequential ultrasound and Doppler screening for signs of fetal anaemia, heart failure and hydrops. Immunoglobulins, antiviral and vaccination are not yet available, but intrauterine transfusion in selected cases can be life saving.

Maternal human parvovirus B19 infection and the risk of fetal death and low birthweight: a case-control study within 35 940 pregnant women

OBJECTIVES

To assess the association between maternal parvovirus B19 infection and fetal death, birthweight and length of gestation.

DESIGN

Case-control study.

SETTING

Population based.

POPULATION

Cases were all 281 women with fetal death within a cohort of 35 940 pregnant woxmen in Norway. The control group consisted of a random sample of 957 women with a live born child.

METHOD

Information on pregnancy outcome was obtained from the Medical Birth Registry of Norway. First trimester serum samples were tested for antibodies against parvovirus B19 (IgM and IgG). In seronegative women, further serum was analysed to detect seroconversion during pregnancy.

MAIN OUTCOME MEASURES

Fetal death, length of gestation and birthweight.

RESULTS

Two of 281 (0.7%) of the women who experienced fetal death and nine of 957 (0.9%) of the controls had presence of IgM antibodies, crude odds ratio 0.8; 95% CI (0.2-3.5). In initially, seronegative women, 3.1% (2/65) with fetal death and 2.6% (8/307) with a live birth seroconverted, crude odds ratio 1.2; 95% CI (0.2-5.7). Presence of maternal parvovirus-specific IgG or IgM antibodies in the first trimester, or seroconversion during pregnancy were not associated with lower birthweight or reduced length of gestation in live born children, but was associated with low birthweight in stillborn offspring.

CONCLUSION

Maternal parvovirus B19 infection was not associated with fetal death in our study. Very few cases of fetal death may be attributed to maternal parvovirus B19 infection.

Seroprevalence of parvovirus B19 IgG in children affected by juvenile idiopathic arthritis

Parvovirus (PV) B19 is the causative agent of the childhood disease erythema infectiosum. An association of PV B19 with chronic arthropathies, sometimes resembling rheumatoid arthritis or juvenile idiopathic arthritis (JIA), has repeatedly been described. Other studies, however, have failed to identify any such relationship. In order to study further whether there is a link between PV B19 and JIA, we determined the prevalence of PV B19 specific IgG antibodies in serum samples from children with rheumatoid diseases and compared it with the prevalence in unaffected children We reasoned that if there is an association between PV B19 and JIA, then the prevalence of PV B19 IgG in the children with JIA should be higher than in the control group. PV B19 IgG status was tested in 406 children with JIA and related diseases, and in 146 children constituting a control group. The percentage of PV B19 IgG positive children was not significantly elevated in the disease subgroups compared with age-matched control groups. In conclusion, our findings do not support the hypothesis that human parvovirus B19 is involved in the pathogenesis of JIA.

Concurrent detection of human herpesvirus type 6 and measles-specific IgMs during acute exanthematic human parvovirus B19 infection

A familial outbreak of human parvovirus B19 infection is described in which serological tests carried out routinely for determining the causal agent of febrile rashes of viral etiology failed to yield a definitive diagnosis. Concurrent detection of serum IgMs to parvovirus B19 and to heterologous viruses such as human herpesvirus type 6 (HHV-6) and measles virus complicated interpretation of the data. IgG avidity tests and investigation and testing for the presence of viral DNA in sera by PCR were required to confirm parvovirus B19. The study stresses the importance of avidity and PCR tests to obtain a firm diagnosis of febrile exanthematic viral diseases.

Parvovirus B19 viral loads in relation to VP1 and VP2 antibody responses in diagnostic blood samples

BACKGROUND

Human parvovirus B19 infection is characterised by high peak viral load levels followed by episodes of prolonged viremia. The risk of transmission of parvovirus B19 by blood or blood products has been increasingly recognised and parameters that can predict the risk of transmission are subject of interest.

OBJECTIVES

This study aimed to study correlations between B19 viral DNA loads and antibody responses to the viral antigens VP1 and VP2 in clinical serum samples.

STUDY DESIGN

A panel of 1610 serum samples from patients clinically suspected from acute B19 infection were analysed. Antibodies were measured by the parvovirus anti-VP1 immuno-fluorescence assay (IFA) and the anti-VP2 enzyme immunoassay (EIA) from Biotrin. B19 viral loads were measured by a real-time PCR using the external WHO standard for DNA quantification.

RESULTS

Positive IgM responses were found in 154 (9.6%) of the 1610 sera tested. Based on the PCR results in a subset of 312 sera, the anti-VP2 EIA IgM showed a better combination of sensitivity/specificity (91%/94%) compared to the anti-VP1 IFA (66%/97%). B19 DNA levels in the sera strongly correlated with the levels of IgM antibodies, all sera with high viral loads (>10(6)IU/ml) having VP2 EIA IgM ratios above 3.0.

CONCLUSIONS

The B19 VP2 IgM ELISA is superior to the B19 VP1 IgM IFA if verified by PCR. Anti-VP2 IgM antibodies in sera are indicative for the presence B19 DNA and can be used to predict high levels of B19 DNA in diagnostic sera.

Human parvovirus B19

Parvovirus B19 (B19) was discovered in 1974 and is the only member of the family Parvoviridae known to be pathogenic in humans. Despite the inability to propagate the virus in cell cultures, much has been learned about the pathophysiology of this virus, including the identification of the cellular receptor (P antigen), and the control of the virus by the immune system. B19 is widespread, and manifestations of infection vary with the immunologic and hematologic status of the host. In healthy immunocompetent individuals B19 is the cause of erythema infectiosum and, particularly in adults, acute symmetric polyarthropathy. Due to the tropism of B19 to erythroid progenitor cells, infection in individuals with an underlying hemolytic disorder causes transient aplastic crisis. In the immunocompromised host persistent B19 infection is manifested as pure red cell aplasia and chronic anemia. Likewise, the immature immune response of the fetus may render it susceptible to infection, leading to fetal death in utero, hydrops fetalis, or development of congenital anemia. B19 has also been suggested as the causative agent in a variety of clinical syndromes, but given the common nature, causality is often difficult to infer. Diagnosis is primarily based on detection of specific antibodies by enzyme-linked immunosorbent assay or detection of viral DNA by dot blot hybridization or PCR. Treatment of persistent infection with immunoglobulin reduces the viral load and results in a marked resolution of anemia. Vaccine phase I trials show promising results.

Baculovirus expression of erythrovirus V9 capsids and screening by ELISA: serologic cross-reactivity with erythrovirus B19

Diagnosis of erythrovirus B19 (B19) relies on serology and the detection of viral DNA. Recently, a distinct erythrovirus isolate termed V9, markedly different from erythrovirus B19 (> 11% nucleotide disparity), was isolated. Standard B19 PCR assays were inconclusive and serologic tests failed to categorize V9 as an acute B19-like infection. Sequencing, combined with PCR studies, have since demonstrated the need for specific and differentiated techniques when examining samples for possible B19 or V9 viremia. The antigenic properties of the V9 capsid proteins have not been characterized previously. To address this question, V9 VP1 and VP2 open reading frames were cloned and expressed in insect cells using a baculovirus vector. Large quantities of purified recombinant V9 capsid protein were produced and electron micrographs revealed self-assembly of V9 VP1/VP2 and VP2 capsids into empty icosahedral erythrovirus-like particles with a diameter of approximately 23 nm. Screening of a panel of 270 clinical samples for the presence of V9 IgM and IgG antibodies in ELISA showed 100% serologic cross-reactivity between B19 and V9 when comparing V9 VP2 capsids to a commercial B19 VP2 assay. This suggests that both a V9 and a B19 antibody response may be diagnosed equally well by ELISA using either V9 or B19 recombinant capsids as antigen source. Retrospectively, translation of the V9 sequence indicates that despite a significant genetic variation on the DNA level, the majority of the discrepant DNA sequence represents silent mutations leading to an amino acid sequence very similar to the known B19 strains (96-97% homology).

Anti-VP1 and anti-VP2 antibodies detected by immunofluorescence assays in patients with acute human parvovirus B19 infection

Acute human parvovirus B19 infection is followed by an antibody response to the structural proteins of the viral capsid (VP1 and VP2). We used 80 sera collected from 58 erythema infectiosum and 6 transient aplastic crisis patients to test IgM and IgG antibodies against these two proteins in an immunofluorescence assay (IFA) using Sf9 cells infected with recombinant baculovirus expressing either VP1 or VP2 antigen. Although less sensitive than IgM capture enzyme immunoassay using native antigen (MACEIA), we could detect anti-VP1 or anti-VP2 IgM antibodies by IFA in 49 patients with acute infection (76.6%). Detection of IgG anti-VP1 and anti-VP2 by IFA, however, was as sensitive as IgG detection by indirect enzyme immunoassay. By applying IgG avidity IFA to sera of the 15 IgM IFA negative patients we were able to confirm acute infection in further 12 cases by IFA. Overall, acute infection was confirmed by IFA in 61 (95.3%) of the 64 patients.

The prevalence of antibody to human parvovirus B19 in pregnant women in Kuwait

Infection with parvovirus B19 during pregnancy is known to be associated with various fetal damage, such as aplastic anemia and hydrops fetalis. Our objective was to study the seroprevalence of parvovirus B19 in the obstetric population in Kuwait and to compare this with that in the adult population in other regions. Blood samples from 1047 pregnant women were used in this prospective study. Information regarding patient's age, parity, nationality and symptoms was obtained at the time of collection of the sample. Blood was tested for IgG and IgM antibodies specific for parvovirus B19 using the ELISA technique. The overall prevalence for IgG and IgM was 53.3 and 2.2%, respectively. IgG seropositivity was higher in non-Kuwaiti women, while IgM antibodies was more frequent in Kuwaiti women. A total of 17.4% of the acutely infected patients were symptomatic. Prevalence of parvovirus B19 infection in Kuwait is comparable with that in the other countries.

Rheumatic manifestations of parvovirus B19 infection

Human parvovirus B19 is an emerging DNA virus. B19 infection is common and widespread. Major manifestations of B19 infection are transient aplastic crisis, erythema infectiosum, hydrops fetalis, acute and chronic rheumatoid-like arthropathy, and, in the immunocompromised host, chronic or recurrent bone marrow suppression. A number of less common manifestations of B19 infection include various rash illnesses, neuropathies, and acute fulminant liver failure. Of rheumatologic interest, B19 infection must be differentiated from early presentation of more classic erosive rheumatoid arthritis and, in some cases, systemic lupus erythematosus. It is unlikely that B19 plays a role in classic erosive rheumatoid arthritis, but understanding pathogenesis of B19 arthropathy may provide insights into the mechanisms by which rheumatoid arthritis develops. Evidence for persistence of B19 infection suggests that human parvovirus B19 infection may serve as a model for the study of virus-host interactions and the role of viruses in the pathogenesis of rheumatic diseases.

Comparative evaluation of three recombinant antigen-based enzyme immunoassays for detection of IgM and IgG antibodies to human parvovirus B19

BACKGROUND

Diagnosis of acute and past infection with parvovirus B19 is based on detection of IgM and IgG antibodies.

OBJECTIVES

To evaluate two commercial recombinant antigen-based enzyme immunoassay (EIA) test kits for detection of IgM and IgG antibodies to parvovirus B19 and to compare the commercial EIAs to in-house EIA test procedures.

STUDY DESIGN

A panel of 121 sera was used to compare the three IgM EIAs. The panel included 84 sera submitted for parvovirus B19 testing and 37 sera that were IgM positive for other viral pathogens. The same serum panel plus an additional 14 sera submitted for B19 testing was used to compare the three IgG EIAs. The commercial EIAs were performed according to manufacturers' instructions. Using the in-house EIA test procedures as the reference, sensitivity and specificity for each of the commercial EIAs was determined.

RESULTS

The commercial B19 IgM EIAs showed agreements of 95.0 and 93.4% to the in-house IgM EIA. Compared to the in-house B19 IgM EIA, the commercial B19 IgM EIAs were 97.4 and 97.5% sensitive, respectively. Specificities were 93.5 and 91.4%, respectively. Sensitivities for the commercial IgG EIAs, compared to in-house IgG EIA, were 88.0 and 85.2%, respectively, and specificities were 94.1 and 98.0%.

CONCLUSION

We found that the commercial parvovirus B19 IgM and IgG EIAs are comparable to standard in-house EIAs and are suitable for testing for B19 antibodies in human sera.

Higher prevalence of parvovirus B19 in Belgian as compared to Tunisian blood donors: differential implications for prevention of transfusional transmission

Serious anaemia can be induced by human parvovirus B19 (HPV) infection in immuno-compromised patients or subjects with an haemolytic disorder. Routine inactivation procedures are insufficient to neutralize the virus, but screening for HPV is an effective means to avoid transmission by transfusion of blood components. In the present study, we have compared for the first time the IgG and IgM seroprevalence in a North African (Tunisian) and Western European (Belgian) population of blood donors. The prevalence of HPV-specific IgM was less than 2% in both populations, pointing to the absence of an epidemic. The prevalence HPV IgG was significantly (p < 0.01) higher in Belgium (74%) than in Tunisia (65%), without any relationship with age or sex. This finding may suggest a south-north gradient of this infectious disease. Since the presence or absence of HPV-specific antibodies does not preclude transfusional transmission, screening for the virus itself should be done to avoid iatrogenic infection in HPV-naive subjects at risk. In view of the different transfusion policies in Belgium and Tunisia, a strategy for each of both countries is proposed.

Infection-related arthritis

Postinfection arthritis represents a significant portion of the referrals to pediatric rheumatology centers, particularly in the United States. Many viral and common bacterial infections can be associated with arthritis, and their recognition can sometimes be difficult on a clinical basis. In patients with acute onset of arthritis, the clinician should actively seek epidemiologic, clinical, or laboratory evidence of infection. Diagnostic tests should be used rationally and results interpreted carefully. Some infections, once recognized, require antibiotic treatment, but in most cases anti-inflammatory therapy is successful in treating articular symptoms.

Comparison of seven commercial tests for the detection of parvovirus B19-specific IgM

Several enzyme immunoassays (EIA) for the detection of parvovirus B19 IgM (anti-B19 IgM) are now commercially available. In this study, seven commercial EIAs (Biotrin, DAKO, Viramed, Viratech, R-Biopharm, Mast) were compared with an in-house EIA (MvP-EIA) using native viral B19 particles and the reference IgM radioimmunoassay (MACRIA). A total of 88 sera were tested. Results agreed in 39/88 (44.3%) sera, whereas 47/88 (53.4%) were discrepant and 2/88 (2.3%) gave an equivocal result. Assay sensitivity ranged from 70.3 to 100% and specificity, from 75.9 to 100%. The best results were obtained with two EIAs (Biotrin, DAKO) using baculovirus-expressed B19 proteins as antigen. This study has shown that baculovirus-expressed B19 antibody tests are suitable tools for detecting anti-B19 IgM.

Evaluation of four commercial enzyme immunoassays for detection of immunoglobulin M antibodies to human parvovirus B19

Four commercial enzyme immunoassays (EIAs) for the detection of parvovirus B19-specific immunoglobulin M (IgM) antibodies [Biotrin Parvovirus B19 IgM (Biotrin International, Ireland); Parvoscan B19 IgM (Euro-Diagnostica, Sweden); Parvovirus IgM (Immunobiological Laboratories [IBL], Germany); and human parvovirus B19 IgM (Hillcrest Biologicals, USA)] were compared to indirect immunofluorescence assay (IFA) and polymerase chain reaction (PCR). Using IFA as the reference test, high sensitivities (> or = 97%) were observed with all four EIAs, though the specificities of the Biotrin and IBL EIAs (99% and 96% respectively) were significantly higher than those of the Hillcrest and Euro-Diagnostica EIAs (81% and 79% respectively).

Comparative evaluation of virological and serological methods in prenatal diagnosis of parvovirus B19 fetal hydrops

Human parvovirus B19 infection in pregnancy represents a potential hazard to the fetus since fetal loss or fetal hydrops can occur. The risk of fetal loss due to transplacental B19 transmission has been evaluated in several studies using different diagnostic methods on maternal and fetal specimens. We analyzed the diagnostic value of virological and serological techniques on maternal serum, fetal cord blood, and amniotic fluid specimens obtained at the time of clinical diagnosis of fetal hydrops in 18 cases of B19 fetal hydrops. B19 DNA was detected by nested PCR, dot blot hybridization, and in situ hybridization assay. Anti-B19 immunoglobulin M and G antibodies were detected by immunoassays using recombinant B19 antigens. Our data suggest that for maternal sera, virological and serological methods have a complementary role in diagnosis, while for fetal specimens the in situ detection of B19 DNA in fetal cord blood is the most sensitive diagnostic system.

Evaluation of serological assays for identification of parvovirus B19 immunoglobulin M

Three different enzyme immunoassays (EIAs) (Parvoscan-B19, IBL parvovirus B19, and IDEIA parvovirus B19) and one immunofluorescence assay (Biotrin Parvo B19 IFA) were evaluated for detection of parvovirus B19 immunoglobulin M (IgM) antibodies in 203 clinical serum samples. An IgM antibody capture radioimmunoassay was used as a reference test. Serum specimens obtained from patients with clinical symptoms suggestive of parvovirus B19 infections were used to evaluate the sensitivities of the assays, which were shown to be comparable for the Biotrin IFA and IDEIA (97%) and lower for the other two EIAs (90%). In order to test the specificity of the assays, clinical serum samples with IgM antibodies against other viruses were examined, as well as sera with rheumatoid factor activity and sera from healthy pregnant women. The specificities of B19 IgM antibody detection were 96% for the Biotrin IFA, 96% for IDEIA, 90% for Parvoscan, and 88% for the IBL assay. These results show that all four assays can be recommended for diagnostic purposes, although false-positive results may be seen with other acute viral infections, healthy pregnant women, and rheumatoid factor-positive samples.