Contribution of a Comparative Western Blot Method to Early Postnatal Diagnosis of Congenital Syphilis

Serology has a pivotal role in the diagnosis of congenital syphilis (CS), but problems arise because of the passive transfer of IgG antibodies across the placenta. The aim of this study was to assess the diagnostic value of a comparative Western blot (WB) method finalized to match the IgG immunological profiles of mothers and their own babies at birth in order to differentiate between passively transmitted maternal antibodies and antibodies synthesized by the infants against Treponema pallidum. Thirty infants born to mothers with unknown or inadequate treatment for syphilis were entered in a retrospective study, conducted at St. Orsola-Malpighi Hospital, Bologna, Italy. All of the infants underwent clinical, instrumental, and laboratory examinations, including IgM WB testing. For the retrospective study, an IgG WB assay was performed by blotting T. pallidum antigens onto nitrocellulose sheets and incubating the strips with serum specimens from mother-child pairs. CS was diagnosed in 11 out of the 30 enrolled infants; 9/11 cases received the definitive diagnosis within the first week of life, whereas the remaining two were diagnosed later because of increasing serological test titers. The use of the comparative IgG WB testing performed with serum samples from mother-child pairs allowed a correct CS diagnosis in 10/11 cases. The CS diagnosis was improved by a strategy combining comparative IgG WB results with IgM WB results, leading to a sensitivity of 100%. The comparative IgG WB test is thus a welcome addition to the conventional laboratory methods used for CS diagnosis, allowing identification and adequate treatment of infected infants and avoiding unnecessary therapy of uninfected newborns.     

Detection of toxoplasma antibodies in sera of Salmonidae by ELISA

Toxoplasma gondii is a protozoan parasite with a worldwide distribution. It is capable of infecting all warm-blooded animals. Toxoplasmosis was not considered a waterborne zoonoses, but recently, it has been reported in many marine mammals. Coastal pollution by sewage from humans and pets has been suggested as a source for toxoplasma infection in these animals. Recent reports of toxoplasmosis in marine mammals raise concern that cold-blooded marine animals are potential sources of T. gondii infection. Conversely, the increasing proclivity for eating fish, crabs, shrimp, and mollusks—raw, undercooked, smoked, or dried—facilitates zoonoses infections caused by protozoan microorganisms; and one of them is toxoplasma. Detection of antibodies against T. gondii can be achieved by different serological tests such as enzyme-linked immunosorbent assay (ELISA). To determine whether toxoplasmosis has a role in Salmonidae infection, which is the most common seafood in Shahrekord district, this research was carried out on 50 Salmonidae aged 4 months (weight 700 ± 200 g). ELISA was performed on serum samples for detecting T. gondii-specific immunoglobulin M (IgM) and immunoglobulin G (IgG). As a result, toxoplasmic IgM antibody was detected in five of 50 samples (cut-off value of ≥0.183). Based on these findings, we believe that Salmonidae may be susceptible to primary T. gondii infection. While there is still no evidence of T. gondii transmission from cold-blooded sea animals to human via consuming their meat or other products, further research can be done to prove the possibility of this hypothesis.     

Value of specific immunoglobulin a detection by two immunocapture assays in the diagnosis of toxoplasmosis

The diagnosis ofToxoplasma gondii infection is currently based on immunological tests, but tests for IgG and IgM antibodies alone are often insufficient to assess the risk of active disease, especially during pregnancy and in immunodeficient subjects. The supplementary diagnostic value of testing for antitoxoplasmic IgA in cases of acute, chronic, congenital and reactivated toxoplasmosis, relative to classical immunological tests, was evaluated using two immunocapture tests, one based on tachyzoite agglutination and the other on an immunoenzymatic complex recognizing the membrane protein P30 ofToxoplasma gondii. A total of 4,541 sera from 395 uninfected subjects, 468 immunized subjects with chronic infection, 117 subjects with acute infection and 403 children, 103 of whom had congenital toxoplasmosis, was tested. Specific IgA tests were negative in the nonimmune population, but tests for this immunoglobulin subtype became positive very rapidly during primary infection, and IgA disappeared more rapidly than IgM. In the children infected in utero, specific IgA was detected more frequently than IgM. In contrast, in a population of HIV-seropositive subjects with clinical toxoplasmosis, tests for IgA were poorly sensitive. The two tests for specific IgA produced similar results, except in the early stages of primary infection, in which immunoenzymatic testing for anti-P30 IgA was less sensitive than the agglutination method.     

Evaluation of an in-house cat scratch disease IgM ELISA to detect <Emphasis Type="Italic">Bartonella henselae</Emphasis> in a routine laboratory setting

Cat scratch disease (CSD) is caused by Bartonella henselae infection and is a common cause of regional lymphadenopathy. The diagnosis of CSD largely depends on serology, but detection of B. henselae in an affected lymph node by PCR is also an important diagnostic tool. We evaluated an IgM in-house ELISA protocol and analyzed its performance in routine CSD serology. Serum samples from PCR-positive patients (n = 126), PCR-negative patients (n = 123), and age-matched controls (n = 126) were used for evaluation. The sensitivity of the IgM ELISA was only 56%, showing that the performance of B. henselae serology under routine laboratory settings is low, probably caused by the wide variability in disease duration in patients suspected of CSD whose samples were submitted to our laboratory. Most patients (46%) with a positive IgM response were between 0 and 20 years of age. We conclude that the serodiagnosis of B. henselae is hampered by the low sensitivity and specificity of the assays when used in a routine laboratory setting. For this reason, a negative IgM or PCR result can never exclude CSD, especially with late sample collection.     

Relevance of B19 markers in serum samples for a diagnosis of parvovirus B19-correlated diseases

In order to evaluate the optimal and essential diagnostic test(s) for a correct diagnosis of B19 diseases, 344 consecutive serum samples were tested from 344 patients with clinical suspicion of B19 infection during an epidemic period (early Spring-Autumn 2000). Sera were tested for B19 DNA by a standardized competitive polymerase chain reaction-enzyme-linked immunosorbent assay (PCR-ELISA) and dot-blot hybridization and for specific IgM and IgG by ELISA. Of 344 patients examined, 125 were positive for markers of B19-associated disease: 49 had both B19 DNA and IgM, 50 had B19 DNA without IgM, and 26 had IgM without B19 DNA. After examination of the different patterns of B19 markers as diagnostic tools for B19 infection, IgM determination detected only 60% of B19-documented infections. IgM tests were nevertheless fundamental, as they were the unique diagnostic marker in 20.8% of documented infections (26 of 125 patients), in the diagnosis of recent, but still symptomatic infections when B19 DNA was no longer detectable. The determination of B19 DNA with PCR permitted detection of 79.2% of infections and therefore represented an essential test. PCR was fundamental for the diagnosis of B19 disease, as the unique diagnostic marker in 32% of documented infections (50 of 125 patients), both in acute infections at the onset of symptoms before the appearance of immunological response, and during the course of persistent B19 infections in which IgM had cleared. The contemporaneous determination of B19 DNA by PCR and specific IgM appears to be the most appropriate diagnostic protocol for the correct laboratory diagnosis of B19 infection.     

Validation of an IgM antibody capture ELISA based on a recombinant nucleoprotein for identification of domestic ruminants infected with Rift Valley fever virus

The presence of competent vectors in some countries currently free of Rift Valley fever (RVF) and global changes in climate, travel and trade have increased the risk of RVF spreading to new regions and have emphasised the need for accurate and reliable diagnostic tools for early diagnosis during RVF outbreaks. Highly sensitive viral detection systems like PCR have a limited use during outbreaks because of the short duration of viraemia, whereas antibodies like specific IgM which are serological indicators of acute infection, can be detected for up to 50 days after infection. Using the highly conserved and immunogenic recombinant nucleoprotein of RVF virus in an IgM capture ELISA, the risk of laboratory infection associated with traditional serological methods is avoided. The use of pre-coated/pre-blocked ELISA plates and the conjugation of the recombinant nucleoprotein with horseradish peroxidase simplified and shortened the assay procedure. Results showed the assay to be highly reproducible with a lower detection limit equal to that of a commercial competition ELISA. By receiver operating characteristic (ROC) curve analysis the area under curve (AUC) index was determined as 1.0 and the diagnostic sensitivity and specificity at a PP cut-off value of 4.1 as 100% and 99.78% respectively. The results of this study demonstrated that the IgM capture ELISA is a safe, reliable and highly accurate diagnostic tool which can be used on its own or in parallel with other methods for the early diagnosis of RVF virus infection and also for monitoring of immune responses in vaccinated domestic ruminants.     

Diagnostic Performance of Serological Tests to Detect Antibodies Against Acute Scrub Typhus Infection in Central India

Background: Differentiating scrub typhus from other acute febrile illness is difficult due to non specificity of clinical symptoms and relative absence of eschar in Indian population. The diagnosis thus relies mainly on laboratory tests. Antibody based serological tests are mainstay of scrub typhus diagnosis. Here, we evaluated the diagnostic performance of IgM ELISA, IgM IFA and ICT to detect antibodies against O. tsutsugamushi in acute serum of febrile patients. Methodology: The serum samples from 600 randomly selected patients suffering from acute undifferentiated fever were tested by all the three tests mentioned above. We used latent class analysis to generate unbiased results as all the tests for scrub typhus diagnosis are imperfect and none of them can be considered as reference standard. Results: We found that IgM ELISA with cutoff titer 0.5 OD has high diagnostic accuracy (sensitivity 99.9% and specificity 99.15) than IgM IFA (sensitivity 96.8% and specificity 99.7%) for scrub typhus diagnosis. ICT used in our study had very high specificity 100% but low sensitivity (38%) which would limit its use for acute serum samples. ICT being a screening or point of care test, has to be more sensitive while some compromise with specificity is affordable. Hence, optimal cutoff for ICT should be evaluated under different settings. Conclusion: IgM ELISA being simple and affordable could be an alternative diagnostic test to IgM IFA which is subjective and costly.     

Recombinant proteins in the diagnosis of toxoplasmosis

Kotresha D, Rahmah N. Recombinant proteins in the diagnosis of toxoplasmosis. APMIS 2010; 118: 529–42. Toxoplasma gondii is an important human pathogen with a worldwide distribution. It is primarily of medical importance for pregnant women and immunocompromised patients. Primary infection of the former is often associated with fetal infection, which can lead to abortion or severe neonatal malformation. Immunocompromised patients are at risk of contracting the severe form of the disease that may be fatal. Thus, detection of T. gondii infection with high sensitivity and specificity is crucial in the management of the disease. Toxoplasmosis is generally diagnosed by demonstrating specific immunoglobulin M (IgM) and IgG antibodies to toxoplasma antigens in the patient’s serum sample. Most of the commercially available tests use T. gondii native antigens and display wide variations in test accuracy. Recombinant antigens have great potential as diagnostic reagents for use in assays to detect toxoplasmosis. Thus in this review, we address recent advances in the use of Toxoplasma recombinant proteins for serodiagnosis of toxoplasmosis.     

Response to Standard Syphilis Treatment in Patients Infected with the Human Immunodeficiency Virus

 In a study designed to evaluate the efficacy of penicillin in HIV-infected patients with syphilis and to determine the clinical and laboratory responses after treatment, 13 patients with HIV infection and syphilis were assessed at enrollment and at the last follow-up examination (median time of 21 months). The Venereal Diseases Research Laboratory (VDRL) test, the Treponema pallidum hemaglutination test, and leukocyte counts in cerebrospinal fluid were evaluated both at enrollment and at the last follow-up visit, and the polymerase chain reaction for Treponema pallidum DNA and the rabbit infectivity test were performed on cerebrospinal fluid samples at the last follow-up visit. Primary syphilis was confirmed in four patients, latent syphilis in five, and neurosyphilis in four. After penicillin treatment, all patients were asymptomatic. The serum rapid plasma reagin test became negative in five patients, and titers declined in eight. The VDRL test, Treponema pallidum DNA, and the rabbit infectivity test were negative in all 13 patients. Except for one patient whose serological titer was slow to decline, all patients had good clinical and serological responses to penicillin. In certain settings, factors other than penicillin treatment failure should be considered in HIV-infected patients with suspected relapse of syphilis.     

Evaluation of the BioPlex 2200 Syphilis System as a First-Line Method of Reverse-Sequence Screening for Syphilis Diagnosis

Despite recent technological advances, the diagnosis of syphilis remains a challenging enterprise. Actually, most high-volume laboratories have adopted the “reverse algorithm” due several factors, including the potential to automate testing. Recently, immunoassays processed on random-access systems have been proposed as screening tests. The purpose of this study was to evaluate diagnostic performances of BioPlex 2200 Syphilis IgG and BioPlex 2200 Syphilis IgM, tests based on Multiplex Flow technology, in comparison with the performance of Architect Syphilis TP, a chemiluminescent immunoassay for the detection of IgG and/or IgM anti-Treponema pallidum antibodies. A retrospective study was performed with a panel of 100 blood donor sera, a panel of 350 clinical and laboratory-characterized syphilitic sera, and 170 samples obtained from subjects with potentially interfering conditions. Moreover, 200 unselected samples submitted to the Microbiology Laboratory of St. Orsola Hospital in Bologna for routine screening for syphilis were evaluated. As confirmatory tests, T. pallidum hemagglutination and Western blot assays were used. Considering the IgG Western blot (WB) assay to be the gold standard method, BioPlex 2200 Syphilis IgG specificity was far higher than Architect Syphilis TP specificity (89.7% versus 78.4%, respectively), whereas the sensitivity was 100% for both automated methods. Compared to the IgM WB assay, BioPlex 2200 Syphilis IgM performed with a specificity of 94.9%, whereas the sensitivity was 84.8%. Considering the excellent ease of use and automation, the high sample throughput and its valuable analytical performances, BioPlex Syphilis 2200 IgG could represent a suitable choice for high-volume laboratories. BioPlex Syphilis 2200 IgM could be considered a good addition to IgG testing for uncovering active infections.     

Detection of chikungunya virus-specific IgM on laser-cut paper-based device using pseudo-particles as capture antigen

The incidence of arbovirus infections has increased dramatically in recent decades, affecting hundreds of millions of people each year. The Togaviridae family includes the chikungunya virus (CHIKV), which is typically transmitted by Aedes mosquitoes and causes a wide range of symptoms from flu-like fever to severe arthralgia. Although conventional diagnostic tests can provide early diagnosis of CHIKV infections, access to these tests is often limited in developing countries. Consequently, there is an urgent need to develop efficient, affordable, simple, rapid, and robust diagnostic tools that can be used in point-of-care settings. Early diagnosis is crucial to improve patient management and to reduce the risk of complications. A glass-fiber laser-cut microfluidic device (paper-based analytical device [PAD]) was designed and evaluated in a proof of principle context, for the analysis of 30 µL of patient serum. Biological raw materials used for the functionalization of the PAD were first screened by MAC-ELISA (IgM capture enzyme-linked immunosorbent assay) for CHIKV Immunoglobulin M (IgM) capture and then evaluated on the PAD using various human samples. Compared with viral lysate traditionally used for chikungunya (CHIK) serology, CHIKV pseudo-particles (PPs) have proven to be powerful antigens for specific IgM capture. The PAD was able to detect CHIKV IgM in human sera in less than 10 minutes. Results obtained in patient sera showed a sensitivity of 70.6% and a specificity of around 98%. The PAD showed few cross-reactions with other tropical viral diseases. The PAD could help health workers in the early diagnosis of tropical diseases such as CHIK, which require specific management protocols in at-risk populations.     

Importance of clinical features in diagnosis of mumps during a community outbreak

Eleven patients with classical clinical features of mumps presented to one practice over a three month period. Initial laboratory testing for mumps virus specific IgM was positive in only two of the eleven cases. On subsequent testing by an additional system, four additional cases were IgM positive. Five were IgM negative by both assays. Some currently used serological tests for diagnosis of mumps virus infection may be negative in a high proportion of patients with clinically apparent mumps. This series illustrates that the time during the acute illness at which testing is performed may be important and that isolated serological tests cannot be relied upon to exclude a clinical diagnosis of mumps.     

Detection of immunoglobulin M antibodies toTreponema pallidum in a modified enzyme-linked immunosorbent assay

The indirect enzyme-linked immunosorbent assay (ELISA) for detection of immunoglobulin M (IgM) antibodies toTreponema pallidum in sera of syphilitic patients is complicated by false positive reactions due to the interference of IgM rheumatoid factor (IgM-RF) activity and the presence of treponemal IgG antibodies. Another source of error producing false negative results is the competition between treponemal IgG and IgM antibodies for the binding sites on the antigen. To avoid these complications in the indirectTreponema pallidum-specific IgM-ELISA, total IgG was immunoprecipitated from sera of syphilitic patients prior to the assay. The IgM-RF from non-precipitated sera reacted in an IgM-RF-ELISA and in theTreponema pallidum-IgM-specific ELISA with identical titers. After precipitation of total IgG no reactíon of the IgM-RF in the assay could be demonstrated. Competition between IgG and IgM antibodies can be prevented almost completely by the precipitation procedure. The sensitivity and specificity of theTreponema pallidum-specific IgM-ELISA after immunoprecipitation of total serum IgG were shown to be higher than 97 percent.     

<Emphasis Type="Italic">Crenosoma vulpis</Emphasis> in dog: first case report in Italy and use of the FLOTAC technique for copromicroscopic diagnosis

Crenosoma vulpis is a metastrongylid nematode that infects the bronchi, bronchioles, and trachea of wild and domestic canids and various other carnivores. It is endemic in the red fox population in the north-eastern parts of North America and in Europe, including Italy. Dogs are susceptible to infection with clinical signs consisting primarily in a chronic cough. The present paper reports—to the authors’ knowledge—the first case of spontaneous C. vulpis infection in a dog in Italy. In addition, it also reports, for the first time, the use of the FLOTAC technique for C. vulpis diagnosis in canine fecal samples, with results compared to the following four standard copromicroscopic techniques: the Baermann technique, the McMaster technique, the simple flotation technique, and the Wisconsin technique. The results showed that the FLOTAC technique produced mean larvae per gram of feces greater than that produced by the other more widely used diagnostic tools. After the treatment of the C. vulpis infected dog with a single oral dose of 0.5mg/kg milbemycin oxime, the clinical signs resolved and the shedding of larvae ceased. In conclusion, the discovery of C. vulpis for the first time in a dog in Italy indicates that the fox lungworm should be considered in the differential diagnosis of respiratory disease in dogs; in addition, the findings of the comparison study showed that the FLOTAC technique may improve the ability to accurately diagnose canine lungworm infections. An erratum to this article can be found at     

Increases of Corporal Temperature as a Risk Factor of Atherosclerotic Plaque Instability

Background This work explores for the first time the effects of temperature increments on the development of high shear stresses between plaque and arterial wall due to their different dilatational properties. Data from the literature report febrile reactions prior to myocardial infarction in patients with normal coronary arteries and that coronary syndromes seem to be triggered by bacterial and viral infections, being fever the common symptom. Methods The thermo-mechanical behavior of thoracic aortas of New Zealand White rabbits with different degrees of atherosclerosis was measured by means of pressure–diameter tests at different temperatures. In addition, specific measurements of the thermal dilatation coefficient of atheroma plaques and of healthy arterial walls were performed by means of tensile tests at different temperatures. Results Results show a different thermo-mechanical behavior, the dilatation coefficient of atheroma plaque being at least twice that of the arterial wall. The calculation of temperature-induced mechanical stress at the plaque–vessel interface yielded shear stress levels enough to promote plaque rupture. Conclusions Increases of corporal temperature either local—produced by the inflammatory processes associated with atherosclerosis—or systemic—by febrile reactions—can play a role in increasing the risk of acute coronary syndromes, and they deserve a more comprehensive study.     

Diagnostic procedures in B19 infection

In immunologic normal hosts, both children and adults, B19 can cause acute, generally self-limiting diseases. The infection leads to a viremia that can be present, at high titre, for about one week, then the onset of a specific immune response controls the infection. B19 infection in pregnancy can be associated with non-immunologic foetal hydrops or foetal death. In immunocompromised hosts, B19 can persist over several months and sometimes years. Persistent or recurrent B19 infections can be associated with chronic clinical manifestations or with transient clinical syndromes, generally related to the recrudescence of viral replication. Since the infection has been associated with a wide variety of clinical manifestations and some clinical features of B19 infection, such as anemia, artropathy and rash, can be common to other pathogens, a laboratory diagnosis of B19 infection is required. A diagnostic protocol must consider both the type of pathology and the type of patient. In immunocompetent individuals serological and virological testing is complementary, while in immunocompromised patients viral detection is the diagnosis of choice. Viral detection methods are generally based, nowadays, on the direct detection of B19 genome in clinical specimens. B19 DNA is mainly detected by hybridizations assays and by the most sensitive PCR assays. Serological diagnosis of B19 infection is generally achieved by detection of IgM and IgG antibodies to the B19 structural proteins VP1 and VP2. IgM detection is most often performed by capture assays, both in EIA and RIA formats, IgG are mainly detected by indirect EIA and immunofluorescence tests.     

Comparison of the sensitivity of imprint and scraping techniques in the diagnosis of American tegumentary leishmaniasis in a referral centre in Rio de Janeiro, Brazil

American tegumentary leishmaniasis (ATL) is an infectious disease that presents a wide spectrum of clinical manifestations making parasitological tests important for its diagnosis. Direct examination, although considered of low sensitivity is still employed mainly in areas with poor laboratory infrastructure. The aim of this study was to standardize the method of collecting and reading the scraping procedure and to then compare sensitivity of this procedure on two sites of the lesion (outer edge—OE and inner edge—IE) and of the imprint against the reference method (isolation in culture) in a group of 110 patients treated at a Referral Center in Rio de Janeiro, Brazil. ATL diagnosis was confirmed in 40 patients (36.4%), 39 cases were caused by L. braziliensis and 1 by L. amazonensis. Imprint was positive in 28 patients and scraping in OE in 17 and in IE in 25 patients, resulting in sensitivity of 70%, 42.5%, and 62.5% respectively. When the three direct examinations were combined, sensitivity value attained 77.5%. Aspects related to ease and quality of the collected material, pain intensity and frequency of bleeding in the scraping procedure were also broached and discussed in this study. The parameters of accuracy presented indicate that the direct methods can be safely used in ATL diagnosis, principally in IE scraping, as it is easy to produce and the examination is not costly, which allows the procedure to be repeated at different moments which, in turn, increases the possibility of finding the parasite. Despite that the direct methods are technically widespread, they are not standardized and the parameters of accuracy are unknown. If we consider the high incidence of leishmaniasis in low-income areas, the implantation of standardized and selective methods would provide advances in the diagnosis of leishmaniasis.     

New advances in the diagnosis of congenital cytomegalovirus infection.

Although the diagnosis of congenital CMV infection is still complex, important goals have been achieved in recent years, among which are: the availability of more reliable IgM tests for screening pregnant women whose pre-pregnancy serological status for CMV is unknown, tests to determine the avidity index of anti-CMV IgG, allowing the diagnosis of a primary CMV infection and innovative and traditional virological tests to detect the virus in amniotic fluid. When a woman is found to be IgM-positive, further diagnostic evaluation focused on determining whether this is due to a primary infection should be carried out. Maternal primary infections that were difficult to determine until a few years ago unless documented by seroconversions can now be readily diagnosed from the presence of low/moderate avidity anti-CMV antibody which persists for approximately 18-20 weeks after primary infection. In mothers at risk of transmitting the virus prenatal diagnosis can be performed between 21 and 22 weeks of gestation, and the amniotic fluid represents the pathological material of choice to determine intrauterine virus transmission. At birth or in the first 2/3 weeks of life, it is essential to use appropriate tests for diagnosis of CMV congenital infection.     

Early neonatal diagnosis of congenital toxoplasmosis: value of comparative enzyme-linked immunofiltration assay immunological profiles and anti-Toxoplasma gondii immunoglobulin M (IgM) or IgA immunocapture and implications for postnatal therapeutic strategies.

Diagnostic strategies for congenital toxoplasmosis have changed profoundly in recent years. Immunological diagnostic methods, long considered disappointing, can now be used at a very early stage. Over a 3-year period, 1,050 infants at risk of congenital toxoplasmosis (born to 1,048 mothers infected during pregnancy) were monitored for a minimum of 12 months and a maximum of 7 years. More than 6,000 serum specimens were analyzed by comparative mother-infant immunological profiles (CIPs) based on an enzyme-linked immunofiltration assay (ELIFA) and an immunocapture method for the detection of specific immunoglobulin M (IgM) and IgA. IgG antibodies were also titrated. One hundred three cases of congenital toxoplasmosis were demonstrated. The CIP-ELIFA method had a better diagnostic yield (sensitivity, 90%) than specific IgM and/or IgA detection by immunocapture assay (sensitivity, 77%). By using a combination of these tests, congenital infection was diagnosed in the first month and the first 3 months of life in 90 and 94% of infants with toxoplasmosis, respectively, with a specificity of 99.8% and a positive predictive value of 99% at 8 months of age. This dual diagnostic approach (ELIFA and IgM-IgA immunocapture) is highly efficient and has important implications for therapy. Indeed, early postnatal diagnosis based on objective evidence enables therapy with pyrimethamine-sulfadoxine to be started immediately for 24 months, while spiramycin (which used to be given preventively for 9 to 12 months to all infants at risk) can be stopped after the first 3 months of life.     

Simultaneous IgM reactivity by EIA against more than one virus in measles, parvovirus B19 and rubella infection.

BACKGROUND: A clinical diagnosis of rash-causing infections is not always possible and reliance has to be placed on serological evidence of infection, especially on the presence of specific immunoglobulin (Ig)M. However, despite the use of modern serological methods and validated commercial kits, reports appear in the literature of simultaneous IgM reactivity against more than one virus in cases of Epstein Barr virus, rubella, cytomegalovirus, human parvovirus B19 (HPV B19) and measles infections, all with implications for the pregnant woman. OBJECTIVES: We decided to evaluate the extent of the problem in rubella, measles and HPV B19 infections in a routine diagnostic laboratory. STUDY DESIGN: We tested sera from cases with initial clinical and serological evidence of infection with measles, HPV B19 or rubella for evidence of simultaneous IgM reactivity against more than one virus. We confirmed primary infections with specific-IgG antibody avidity tests, and subjected sera with IgM reactivity against more than one virus to avidity tests to identify which, if any, of the three viruses was the cause of the primary infection. Groups of monoreactive IgM sera were randomly selected from the presented sera to demonstrate that the avidity of the IgG specific for the other two viruses would be of high avidity compared with the low avidity of the IgG specific for the virus against which specific IgM had been detected. RESULTS: Our results confirm that simultaneous IgM reactivity against more than one virus does occur in these three infections, and that this is unlikely to be caused by the presence of rheumatoid factor. CONCLUSIONS: In the absence of seroconversion, reliance on specific IgM results alone for diagnosis of these infections should be avoided and tests such as specific IgG antibody avidity should also be employed. The simultaneous occurrence of IgM reactivity against more than one virus is also important for epidemiological and surveillance reasons as the widespread use of the mumps, measles and rubella vaccine makes its impact on the population. Falsely diagnosed cases of apparent measles or rubella could throw into question the efficacy of the vaccine.