Diagnostic Accuracy of Two Molecular Tools for Diagnosis of Congenital Chagas Disease.

BACKGROUND AND OBJECTIVE: The real prevalence of congenital Chagas disease is undefined because of difficulties in the detection of Trypanosoma cruzi by microscopic examination. The aim of this study was to determine the diagnostic accuracy of two molecular diagnostic tools, qPCR and LAMP, in the diagnosis of congenital Chagas disease in a clinical setting. METHODS: To this end, we conducted a prospective cohort study in a tertiary care center, of infants under 9 months of age, born in Buenos Aires to women with Chagas disease. Blood samples were collected for microscopic examination and molecular diagnosis at baseline. If negative, infants were followed up until 9 months of age to determine a final diagnosis by serology. In-house qPCR and LAMP previously validated were challenged as index tests. RESULTS: A total of 154 participants were potentially eligible, 120 of whom were enrolled. Finally, 102 (66.2%) of them fulfilled the follow-up. The diagnosis of congenital Chagas disease was confirmed in 13 infants and excluded in 89. Both the sensitivity and specificity of the qPCR were 100.0% (95% confidence interval 75.3-100.0 and 95% confidence interval 95.9-100.0, respectively), whereas the sensitivity and specificity of LAMP were 69.2% (95% confidence interval 38.6-90.9) and 100% (95% confidence interval 95.9-100.0), respectively. CONCLUSIONS: The qPCR agreed with the current diagnostic algorithm, and was a reliable and sensitive tool to detect congenital Chagas disease earlier, providing an appropriate and timely identification of infected infants requiring treatment. LAMP was able to detect congenital Chagas disease in infected infants by naked-eye visualization in accordance with a microscopic examination. The advantages of molecular diagnostic tools should be taken into account by the health system to improve congenital Chagas disease diagnosis.

Acquired Syphilis by Nonsexual Contact in Childhood.

BACKGROUND: Children may acquire syphilis by nonsexual contact as a consequence of close and repetitive contact with mucosal or skin lesions of people with active syphilis. METHODS: Prospective cohort study of pediatric patients with acquired syphilis by nonsexual contact. Demographics, clinical findings, posttreatment serology development and general laboratory data were collected. Sexual transmission was ruled out after a careful medical and psychosocial evaluation of the patient and his/her family. RESULTS: Twenty-four patients were included in the study. Mean age at diagnosis was 4.2 years old. All of them came from overcrowded households with poor hygiene conditions. The most frequent reason for consultations was secondary syphilis skin lesions (79.2%). The psychosocial evaluation of children and their families did not reveal signs of sexual abuse in any of the cases. Seventy-eight families and their cohabitants were evaluated, 23 (29.5%) resulted positive for rapid plasma reagin and treponemal test of hemagglutination; 60.9% of the cases were asymptomatic. The symptomatic relatives showed lesions of secondary syphilis. A sustained fall on nontreponemal antibodies titer (rapid plasma reagin) was observed after treatment, becoming negative in 6/24 (25%) cases within 12 months posttreatment. DISCUSSION: Following evaluation, it was considered that sexual abuse was unlikely. However, if examination and psychosocial evaluation do not support it, other ways of transmission must be considered. Overcrowded and poor household conditions boost the risks for nonsexual treponema transmission. An infected member of the family or a caretaker are a particular risk to an infant due to common practices such as using saliva to moisten the rubber nipples of the milk bottles or trying the food temperature using the lips before feeding the infants.

Congenital chagas disease: Development and assessment of a specific IgM capture-based assay for diagnosis of transmission.

Transplacental transmission by Trypanosoma cruzi (T. cruzi) infection can be effectively treated if parasiticide drugs are administered as early as possible during childhood. Furthermore, an ideal situation would be to diagnose the infection near birth in order to avoid the loss of patients during the subsequent follow-up. These situation are desirable due to the maximum benefit of drugs in early stages which, consequently, implies a relevant contribution to eliminate mother-to-child transmission. However, available techniques for that purpose have limitations as being operator-dependent (microhematocrit), require several months follow-up (IgG detection) or specialized laboratories (PCR). In this study we propose to detect specific IgM antibodies (Ab) by developing a capture-based ELISA employing an improved antigen (Ag) to diagnose the transplacental transmission of T. cruzi, and in consequence, to enhance access to effective treatment. Firstly, a new chimera Ag (CP4) was obtained from the fusion of CP1 and CP3 protein, carrying FRA, SAPA, MAP, TSSAII/V/VI and TcD Ag from T. cruzi. Then, we optimized the assay by capturing IgM Ab with a polyclonal anti-IgM Ab and evaluating three Ag formulations to detect specific IgM bound. The formulations were formed as follows: i) F1: CP1 and CP3; ii) F2: CP1, CP3, B13 and P2ß; iii) F3: by CP4. Detection of Ab-binding Ag was carried out using an anti-His Ab since all Ag were expressed with a His-tag. The evaluation panel consisted of sera from vertically infected children under 1-year-old (6 younger than 15 days, 7 older) and samples from non-infected children of women with chronic Chagas Disease. The ELISA assay employing CP4 showed better performance with notable high sensitivity and specificity (92.3% and 93.9%, respectively). Positive and negative likelihood ratios of the test (15.2 and 0.082) suggest its potential clinical relevance in term of post-test probability of infection. In conclution, we developed a standardized and non-operator dependent test to detect specific anti-T. cruzi IgM Ab. Although increased sample size is needed for its validation, our results indicate that this capture-based technique employing CP4 Ag can certainly improve the diagnosis of connatal infection.