The Microscopic Agglutination Test (MAT) Is an Unreliable Predictor of Infecting Leptospira Serovar in Thailand

Abstract

Abstract. A prospective study in Thailand identified 106 patients with culture-proven leptospirosis. The accuracy of the microscopic agglutination test (MAT) in predicting the infecting serovar was evaluated in 78/106 (74%) patients with a diagnostic titer. MAT correctly determined the infecting serovar in 26 cases (33%), indicating that this assay is a poor predictor of infecting serovar in our setting.Leptospirosis is an acute febrile illness caused by pathogenic members of the genus Leptospira . This disease has a worldwide distribution but is most common in tropical regions, including Thailand. [1][2][3][4][5] In a prospective observational study of undifferentiated fever in 845 patients in rural Thailand, leptospirosis was reported to be responsible for 36.9% of cases.4 Leptospira isolation is the gold standard for confirmation of leptospirosis in humans. This provides definitive identification of the infecting serovar and is an important technique for the study of outbreaks and global epidemiology. It has a number of significant drawbacks, however, including low diagnostic sensitivity, prolonged culture period, and the associated expertise necessary for identification of the infecting serovar together with related costs.The microscopic agglutination test (MAT) is commonly used to reach a serologic diagnosis of leptospirosis and is performed by detecting agglutinating antibodies by mixing patient serum with a panel of Leptospira serovars that are considered to be representative of the endemic strains for a given region. 3A positive diagnostic result for the MAT is a 4-fold change in titer or a single pre-defined titer. MAT has also been used to provide an indication of the presumptive serovars causing leptospirosis in a given region. The ability of MAT to accurately determine the prevalent serovars was called into question by a retrospective study conducted in Barbados where disease in 151 individuals was caused by four serovars ( L. kirschneri serovar Bim, L. interrogans serovar Copenhageni, L. borgpetersenii serovar Arborea, and L. noguchii serovar Bajan); serologic analysis was found to have a low degree of accuracy for determining the infecting serovar in this setting. 6 The epidemiology of infecting isolates in Thailand differs markedly, with a recent study showing that the majority of human disease was caused by L. interrogans serovar Autumnalis. 7 The aim of this study was to determine whether MAT provides an accurate guide to the infecting serovars of Leptospira in Thailand.A prospective study was conducted in hospitals situated in six provinces in northeast Thailand (Udon Thani, Burirum, Loei, Nakhon Ratchasima, Maha Sarakham, and Yasothon) between October 2000 and December 2006 to identify patients with culture proven leptospirosis. The study protocol was approved by the Ethical Committee of the Ministry of Public Health, Royal Government of Thailand. Admitting physicians were asked to recruit patients of all ages who they suspected on clinical grounds to have leptospirosis. Clinical features cons...

Outbreak of Leptospirosis after a Race in the Tropical Forest of Martinique

“…1,13,14 Studies in Barbados and Thailand emphasized that the accuracy of the MAT in predicting the infecting serovar was poor in individual cases of leptospirosis. 15,16 Paradoxical reactions and cross-reactions between serogroups may explain the difficulty to infer the identity of the infecting leptospiral serovar or serogroup. However, presumptive serogroup reactivity data could be used to gain a broad idea of the serogroups present at the population level.…”

Similarities in Leptospira Serogroup and Species Distribution in Animals and Humans in the Indian Ocean Island of Mayotte

“…We suggest that post-vaccinal titers persisted after annual (sometimes bi-annual) vaccinal injection and remain at high levels ( 1,600) because frequent exposures to field strains occur. [23][24][25] One "non-vaccinated" dog showed seropositivity at titer 800 to serogroup Icterohaemorrhagiae. This dog was an adopted adult, thus, we suggest that this animal may have previously been vaccinated.…”

A retrospective analysis of the leptospirosis research in Colombia

“…Based on the results reported for Colombia and considering: 1) that more than 80% of the studies on the prevalence of the disease were based on the MAT, 2) the difficulties of interpreting the MAT and low titers, and 3) the doubtful results on the efficacy of diagnostic tests, including the MAT [11][12][13][14][15], it can be concluded that the real prevalence of the disease in the country is still unknown and that there is a need to continue to search for methods that can accurately assess its prevalence. Work at molecular level is revealing interesting results in various parts of the world and should be considered in future works [10][11][12][13][14][15][16].…”

“…Other methods include: dark field examination, immunofluorescence, culture, Elisa IgM, dot Elisa, and polymerase chain reaction (PCR). The literature on these methods is extensive, and several authors have discussed the advantages and limitations of each method, as well as the discrepancies between the diagnostic results [10][11][12][13][14][15][16].…”