Impact of pre-analytical variables in the determination of serum galactomannan.

Invasive aspergillosis (IA) is associated with a high morbidity and mortality. Since Aspergillus species are usually not cultured in these patients, presumptive diagnosis of IA is more commonly based on galactomannan (GM) detection. Several factors are known to cause false-positive results in the GM test, but little is known on the influence of pre-analytical variables interfering on the test. Here we studied the influence of temperature and sample storage duration in GM results, using samples known to be negative and positive (spiked) for GM. We also evaluated the effect of hemolysis and hyperbilirubinemia on GM optical indexes. We found no influence of storage time (up to 96 h) and temperatures (refrigerated vs. RT) on GM results. However, bilirubin (P = .022) and haemoglobin (P = .003) content influenced GM readings in samples known for being GM positive and negative at baseline, respectively. We conclude that the Platelia GM test does not suffer major influence of pre-analytical variables such as storage conditions, and low levels of hemolysis and hyperbilirubinemia. Nonetheless, massive haemolysis seems to interfere with GM readings in GM-negative samples, and high levels of bilirubin can affect GM readings in samples that are positive for GM at baseline. These findings may facilitate logistics and the implementation of standard operational procedures in clinical laboratories.

Histoplasmosis, An Underdiagnosed Disease Affecting People Living With HIV/AIDS in Brazil: Results of a Multicenter Prospective Cohort Study Using Both Classical Mycology Tests and Histoplasma Urine Antigen Detection.

BACKGROUND: Histoplasmosis is highly endemic in the American continent. This condition is associated with a high mortality, particularly in people living with HIV/AIDS (PLWHA). Diagnosis of histoplasmosis is usually late in South America, as Histoplasma antigen detection is rarely available. Here we determined the prevalence, risk factors, and outcome of histoplasmosis in PLWHA in Brazilian hospitals. METHODS: This was a prospective cohort study (2016-2018) involving 14 tertiary medical centers in Brazil. We included hospitalized PLWHA presenting with fever and additional clinical findings. Patients were investigated at each participant center with classical mycology methods. Also, Histoplasma antigen detection was performed in urine samples (IMMY). Probable/proven histoplasmosis was defined according to European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group/National Institute of Allergy and Infectious Diseases Mycoses Study Group criteria. RESULTS: From 616 eligible patients, 570 were included. Histoplasmosis was identified in 21.6% (123/570) of patients. Urine antigen testing increased the diagnostic yield in 53.8%, in comparison with standard mycology methods. Variables independently associated with histoplasmosis were CD4+ count <50 cells/mm3, use of an antiretroviral (protective effect), and sample collection in the Northeast region of Brazil. Dyspnea at presentation was independently associated with death. Histoplasmosis was more frequent than tuberculosis in patients with low CD4+ counts. Overall 30-day mortality was 22.1%, decreasing to 14.3% in patients with antigen-based diagnosis. CONCLUSIONS: Histoplasmosis is a very frequent condition affecting PLWHA in Brazil, particularly when CD4+ counts are lower than 50 cells/mm3. Antigen detection may detect earlier disease, with a probable impact on outcomes. Access to this diagnostic tool is needed to improve clinical management of PLWHA in endemic countries.

Clostridium difficile infection in Brazil: a neglected problem?

The epidemiology of Clostridium difficile infection is virtually unknown in Brazil. In this prospective study, 8.3% of patients with nosocomial diarrhea were found to have toxigenic strains of C difficile in their feces. The relevant risk factors for Clostridium difficile infection were receipt of solid organ transplantation and septic shock.

Discrepancies among three laboratory methods for Clostridium difficile detection and a proposal for their optimal use.

Clostridium difficile is the major cause of nosocomial diarrhoea. Several detection methods are available for the laboratory diagnosis of C. difficile, but these vary in terms of sensitivity and specificity. In this study, we compared the performance of three following laboratory tests to detect C. difficile: in-house real-time PCR aiming for toxin B gene (tcdB), EIA for detection of toxins A and B (Premier Toxins A & B) and C. difficile culture in selective medium (bioMerieux). Our results were grouped into three categories as follows: (1) C. difficile-associated diarrhoea (CDAD); (2) asymptomatic carriers; and (3) negative results. Among the 113 patients included in the study, 9 (8.0%) were classified as CDAD, 19 (16.8%) were asymptomatic carriers, 76 (67.2%) had negative results and 9 (8.0%) could not be categorized (positive test for C. difficile toxins only). PCR was found to be the most sensitive diagnostic test in our study, with the potential to be used as a screening method for C. difficile colonization/CDAD. Diagnosis of CDAD would be better performed by a combination of PCR and EIA tests.