Tests diagnostiques de l'infection à Coronavirus (COVID-19) : des atouts et des limites

Le monde entier fait face à une crise sanitaire sans précédent due à la pandémie de maladie à virus SARS-COV-2 alias COVID-19. Malgré les connaissances très incomplètes sur la COVID-19, on a constaté une contagiosité interhumaine élevée au début de la pandémie actuelle, et on estime que chaque nouveau cas de COVID-19 infecte en moyenne deux à trois personnes. En conséquence, la stratégie de lutte contre la pandémie à COVID-19 qui ébranle nos sociétés passe nécessairement par une intensification des tests de détection de l'infection. Ces tests diagnostiques de la COVID-19 sont un outil essentiel pour suivre la propagation de la pandémie. Ainsi, l'objectif de la présente revue de la littérature est d'aborder le diagnostic de l'infection à Coronavirus (COVID-19) en s'attardant sur les tests de diagnostic, leurs atouts et leurs limites. Il y a deux catégories de test : ceux qui recherchent la présence directe du virus ou de ses fragments, et ceux qui recherchent les anticorps résultant de l'infection par le virus du COVID-19. Le test real time ­Reverse Transcriptase ­Polymerase chain reaction (rt-RT-PCR) reste le gold standard pour le diagnostic de la COVID-19. Sa sensibilité sur les écouvillons nasopharyngés semble élevée, mais des faux négatifs peuvent se produire, avec une fréquence incertaine (environ 30% des cas). Les tests sérologiques détectent les anticorps spécifiques du SARSCoV-2. Ils permettent l'identification des individus qui ont été infectés par le virus, se sont rétablis, et ont développé, en théorie, une réponse immunitaire efficace contre le virus. Ils constituent des tests d'orientation diagnostique de la COVID19. A ce jour, aucun de ces tests n'est fiable à 100 %, mais, utilisés par un personnel médical qualifié et en combinaison, ils permettent l'identification de la majorité des individus infectés et immunisés

Prevalence of Positive Coeliac Serology in a Cohort of South African Children with Type 1 Diabetes Mellitus

Background. Coeliac disease (CD) is characterised by immune-mediated damage to the mucosa of the small intestine. Both CD and type 1 diabetes (T1D) have common auto-immune origins. Many patients with CD and T1D are asymptomatic or present with only mild symptoms; hence early diagnosis may only be facilitated by serological screening. Distal duodenal biopsy remains the gold standard for confirming the diagnosis. Objective. To describe the prevalence of CD in T1D patients presenting to the paediatric endocrine service at Inkosi Albert Luthuli Central hospital (IALCH) in Durban and document the relationship between positive coeliac serology and small-bowel biopsy results.Methods. A retrospective chart review was done at IALCH; the paediatric tertiary referral centre for KwaZulu-Natal (KZN) Province. The study sample included all patients with newly diagnosed T1D diagnosed between January 2008 and December 2011.Results. A total of 120 newly diagnosed T1D patients were included in the study; of whom 49 (40.8%) were coeliac serology positive and 61 (50.8%) serology negative. There was no significant difference between the two groups regarding mean age of presentation with diabetes; race; sex; urban v. rural origin and baseline anthropometric measurements. Of patients in the serology-positive group; 97.6% had no symptoms suggestive of CD. Of the 49 patients who were coeliac serology positive; 8 (16%) were biopsied: 3 (37.5%) were positive; 1 (12.5%) had intra-epithelial lymphocytes and 4 (50%) were negative. There was a strong positive correlation between biopsy results and titres of endomysial antibody results (p=0.047). Conclusion. There is a high prevalence of coeliac serology positivity in newly diagnosed T1D patients in KZN. This study provides evidence for screening of children with T1D for CD; and also confirms the low prevalence of symptoms

Superiorite du polymorphisme du systeme HLA par la biologie moleculaire sur le polymorphisme par la serologie aux Cliniques Universitaires de Kinshasa

Le present travail a consiste en l'etude sur systeme HLA de classe II dans la population congolaise. Quatre vingt douze echantillons provenant des sujets sains on ainsi ete types par des methodes de Biologie moleculaire; en utilisant la technique de PCR-SSO et en comparant les resultats a ceux obtenus; par la methode serologique; dans la meme population. Trente et un; 16; 16 et 14 alleles ont ete respectivement reveles aux loci DR; DP et DQ alors que la methode serologique n'avait detecte que 11 et 3 alleles aux loci DR et DQ respectivement et aucun allele au locus DP. Parmi les alleles observes; les plus frequents sont DRBI*1501 pour le locus DRB1; DQB1*0602 pour le locus DQB1 et DPB1*01011 pour le locus DPB1. Ces resultats montrent que le polymorphisme HLA etudie par la Biologie moleculaire est de loin plus etendu que lorsqu'on l'etudie par les methodes serologiques ou celles d'Immunologie cellulaire

Seroprevalences des maladies zoonotiques chez les pasteurs nomades et leurs animaux dans le Chari-Baguirmi du Tchad

The sero p revalences of brucellosis and Q-fever we re eva l u ated in humans and live s t o ck in three Chadian nomadic commu n i t i e s ; i . e. ; Fulani cattle bre e d e rs and A rab camel and cattle bre e d e rs. The survey was carried out in 1999 and 2000. The total number of human sera and animal sera tested were 911 and 1 637; respectively; for antibodies against Brucella spp. and 368 and 613; respectively; for Coxiella burnetii. Sixteen brucellosis positive human sera resulted in a seroprevelance rate of 2. Male participants were significantly more often brucellosis seropositive than females. No association was found between brucellosis serostatus and physical findings or reported symptoms. Positive brucellosis serology was more frequent in c attle (seropreva l e n c e;7) than in camels (1.4) and small ruminants (0.5). Fifteen human sera from 11 A rab camel bre eders and 4 Arab cattle breeders were positive for Q-fever (seroprevalence below 1). Being a camel breeder was a significant risk factor for Q-fever seropositivity. Camels had the highest Q-fever seroprevalence (73) among livestock species

Recherche de reservoirs de la leptospirose a Madagascar par la technique d'amplification genique

"Use of the polymerase chain reaction technique in detection of Leptospirosis in Madagascar"" : A polymerase chain reaction (PCR) technique was used for detection of the Leptospira interrogans rrs gene in kidney tissue from 115 rats; 50 zebu cattles and 13 pigs in an attempt to identify a possible animal reservoir of leptospirosis in Madagascar. In addition; serological testing of 105 individuals in close contact with animals was carried out. The PCR analysis was negative for all the samples tested and only one person was found seropositive at a low titer. The findings suggest that leptospirosis; if prevalent in Madagascar; is likely rare."

Avidite des IgG anti Toxoplasma gondii. Etude en vue d'etablir un nouvel arbre decisionnel dans le depistage de la maladie

Interest of IgG avidity in the diagnosis of toxoplasmosis : Toxoplasmosisinfection is commonly asymptomatic; but it may have severe teratogenic consequences. The authors review the literature on serologic screening in the first trimester of pregnancy

Serological detection of brucellosis among febrile, malaria-negative children and domesticated dogs in an urban African setting

Background: Childhood brucellosis and malaria are co-endemic febrile illnesses in some sub-Saharan African countries. Malaria and brucellosis co-infection or brucellosis sole infections are often missed due to an over emphasis on malaria and the lack of appropriate diagnostic infrastructure. Brucellosis in dogs is usually overlooked and yet there is extensive contact between humans and their pets.Objective: This study investigated brucellosis in children and dogs using a confirmatory serological testing series that screens for three Brucella sp.Methods: Residual blood samples from malaria smear-negative febrile children were collected and tested for Brucella sp and malaria parasite. During the same period, residual blood samples presented to a veterinary microbiology laboratory in the same area were tested for brucellosis using the same approach.Results: A total of 105 human and 80 canine blood samples were tested for brucellosis antibodies. The seroprevalence of brucellosis was 22.86% (25/105) in children and 1.3% (1/80) in dogs using the Card, buffered acidified plate antigen, and standard plate agglutination tests but was 0% using the rivanol precipitation plate agglutination test.Conclusion: Given that brucellosis can be caused by both smooth and rough colony strains, there is a need to modify the current serological surveillance strategy (targeted at only Brucella abortus and other smooth colony Brucella strains) to figure out the relative contribution of rough colony Brucella strains (B. ovis and B. canis). Since Uganda is endemic for brucellosis there is a need to modify the brucellosis surveillance strategy