Background/Objectives: Leptospirosis is a zoonotic disease that is widely distributed around the world and presents symptoms similar to other febrile illnesses in tropical regions, which complicates clinical diagnosis. This study aimed to evaluate the performance and agreement between serological diagnostic tests for detecting both acute and convalescent human leptospirosis, using the micro agglutination test (MAT) as a reference in an endemic region of the Colombian Caribbean. Methods: A prospective descriptive study was conducted on 275 participants with suspected leptospirosis. Paired serum samples were obtained, and an epidemiological survey was conducted. Using the MAT as the gold standard, we calculated positive and negative predictive values, sensitivity, specificity, and kappa index. A Bayesian latent class model was also used to compare the diagnostic tests. Results: In 223 paired serum samples, the sensitivity values for various stages of the disease ranged between 10.8% to 54.1% in the acute and 6.1% to 66.7% during the convalescent phase compared to the MAT. According to the Bayesian model, sensitivity was 9.5% to 75.3% in the acute phase and 5.7% to 85.3% in the convalescent phase. The Kappa value, an indicator of agreement, was moderate for the IgM ELISA in the acute phase (0.553) and substantial in the convalescent phase (0.692). Conclusions: The MAT was the best confirmatory test in both acute and convalescent phases of leptospirosis. Despite the high specificity of ELISA, 21.62% of participants identified as negative by IgM-ELISA in both phases were subsequently confirmed as positive by the MAT. It is necessary to re-evaluate diagnostic guidelines that do not employ the MAT for confirmation and to enhance the diagnostic and clinical identification of leptospirosis within healthcare institutions and public health laboratories while providing a rapid and reliable test for its implementation.

Background/Objectives: Leptospirosis is a globally distributed zoonosis with symptomatology similar to other febrile syndromes in tropical countries, making clinical diagnosis difficult. This study aimed to analyze the performance and agreement between serological diagnostic tests for the detection of acute and convalescent human leptospirosis compared to the micro agglutination test (MAT) in an endemic region of the Colombian Caribbean. Methods: A prospective descriptive study was conducted on 275 patients with suspected leptospirosis. Paired serum samples were collected, and an epidemiological survey completed. Positive and negative predictive values, sensitivity, specificity, and kappa index were calculated using MAT as the gold standard. A Bayesian latent class model was used to compare the diagnostic tests. Results: In 223 paired serum samples, the sensitivity values for different stages of the disease varied between 10.8% to 54.1% in the acute and 6.1% to 66.7% in the convalescent phase when compared to MAT; and when using the Bayesian model 9.5% to 75.3% in the acute and 5.7% to 85.3% in the convalescent phase. The Kappa value, an indicator of agreement, was moderate for the IgM ELISA (0.553) in the acute phase, and substantial (0.692) in the convalescent phase. Conclusions: MAT was the best confirmatory test in both acute and convalescent phases. Despite the high specificity of ELISA, 21.62% of patients diagnosed as negative by IgM-ELISA in the acute and convalescent phases were confirmed as positive by MAT. It is necessary to re-evaluate diagnostic guidelines that do not employ MAT for confirmation, and to strengthen diagnostic and clinical identification of leptospirosis in healthcare institutions and public health laboratories, while providing a rapid and reliable test for its implementation.