Histoplasmosis is a common endemic mycosis in the Americas, often causing severe disease in patients with AIDS. Antigen detection has become an important method for rapid diagnosis of histoplasmosis in the United States but not in Central or South America. Isolates from patients in the United States are predominantly found to be class 2 isolates when typed using the nuclear gene YPS3, while isolates from Latin America are predominantly typed as class 5 or class 6. Whether infection with these Latin American genotypes produces positive results in the Histoplasma antigen assay has not been reported. In this study, we have compared the sensitivity of antigen detection for AIDS patients from Panama who had progressive disseminated histoplasmosis to that for those in the United States. Antigenuria was detected in the MVista Histoplasma antigen enzyme immunoassay (EIA) in 95.2% of Panamanian cases versus 100% of U.S. cases. Antigenemia was detected in 94.7% of the Panamanian cases versus 92% of the U.S. cases. Two clinical isolates from Panama were typed using YPS3 and were found to be restriction fragment length polymorphism class 6. We conclude that the MVista Histoplasma antigen EIA is a sensitive method for diagnosis of histoplasmosis in Panama. Progressive disseminated histoplasmosis (PDH) is a common and serious opportunistic disease among patients with AIDS in the United States and Latin America. In Panama, PDH occurred in 8% of hospitalized patients from 1997 to 2003 and was fatal in 12% of cases (6). The clinical picture was similar to that reported elsewhere and usually included fever, weight loss, and respiratory symptoms, often in association with diarrhea, as well as hepatosplenomegaly, hepatic enzyme elevation, and pancytopenia. Skin lesions were noted in 17% of the Panamanian cases (6), lower than the observed rate for cases from Brazil (66%) but higher than that for cases from the United States (ϳ3%) (7). Disease in patients in Mexico and Latin America has been described as being caused by isolates of Histoplasma capsulatum var. capsulatum that exhibit distinct genetic profiles in comparison to those from the United States (3, 8, 9). Keath et al. (9) first described typing based upon restriction fragment length polymorphism (RFLP) in the YPS3 gene. They showed that Panamanian strains were typed as YPS3 class 3, 5, or 6, while the North American strains were predominantly class 2. Later, Kasuga et al. used the DNA sequence substitution rates in four independent protein-coding genes to identify at least eight different genotypes, or clades (8). North American class 2 was the predominant genotype in the United States and Latin American group A in Latin America. Latin American group B was found only in Columbia and Argentina. Based on only four isolates from Panama included in the study by Kasuga et al., Panamanian strains included Latin American group A and a lone lineage, designated H81. The diagnosis of PDH relies on demonstration of the organism in clinical specimens or detection of antigen in body fluids (2). Histopathology may be falsely negative in up to 50% of patients, caused by sampling error, paucity of organisms, or inexperience of the pathologist. Culture may require several weeks to isolate and identify the organism and may be falsely negative for 15% of patients (13). Antigenuria can be detected in 95% of cases in patients with AIDS in the United States (4, 13) but has not been evaluated in Latin America. Whether genetic differences in Latin American isolates would affect the sensitivity for diagnosis by antigen detection is unknown. The prevalence of PDH in AIDS patients from Panama offered the opportunity to address this question. MATERIALS AND METHODS Case definition. The definition included the presence of AIDS based upon a serologic test positive for human immunodeficiency virus infection, a CD4 cell count below 200 cells/l and/or a previous AIDS defining condition according to CDC classification, and PDH proven by culture or histopathology. Methods. We collected samples of serum and urine from Panamanian patients with AIDS and clinical suspicion of PDH who were admitted to the AIDS ward of the Arnulfo Arias Madrid Hospital in Panama City, Panama, from December 2005 through November 2006. All of the samples were taken before the start of antifungal therapy, referred to as baseline, and then stored frozen at Ϫ20°C. Samples were shipped in batches to MiraVista Diagnostics on three occasions during the course of the study, according to International Air Transport Association regulations. We included 21 patients with PDH in the study. The study was approved by the institution's review board and followed guidelines for clinical research. All patients read and signed an informed-consent form before the samples were taken. The investigators also completed a case report form for each patient with demographic and clinically relevant data. For comparison, paired serum and urine specimens collected at enrollment or week 1 or 2 of treatment from 65 AIDS patients in the United States with PD
