ÿþ<HTML><HEAD><TITLE>XI International Meeting on Paracoccidioidomycosis</TITLE><link rel=STYLESHEET type=text/css href=css.css></HEAD><BODY aLink=#ff0000 bgColor=#FFFFFF leftMargin=0 link=#000000 text=#000000 topMargin=0 vLink=#000000 marginheight=0 marginwidth=0><table align=center width=700 cellpadding=0 cellspacing=0><tr><td align=left bgcolor=#cccccc valign=top width=550><font face=arial size=2><strong><font face=Verdana, Arial, Helvetica, sans-serif size=3><font size=1>XI International Meeting on Paracoccidioidomycosis</font></font></strong><font face=Verdana size=1><b><br></b></font><font face=Verdana, Arial,Helvetica, sans-serif size=1><strong> </strong></font></font></td><td align=right bgcolor=#cccccc valign=top width=150><font face=arial size=2><strong><font face=Verdana, Arial, Helvetica, sans-serif size=1><font size=1>Resume:50-1</font></em></font></strong></font></td></tr><tr><td colspan=2><br><br><table align=center width=700><tr><td><b>Poster (Painel)</b><br><table width="100%"><tr><td width="60">50-1</td><td><b>Effects of inactivation or pretreatment of serum samples in the performance of latex agglutination test for the serodiagnosis of paracoccidioidomycosis (PCM)</b></td></tr><tr><td valign=top>Authors:</td><td><u>Fabíola Silveira Gomes </u> (UFPA - Universidade Federal do ParáIEC - Insituto Evandro Chagas) ; Maurimélia Mesquita da Costa (IEC - Insituto Evandro Chagas) ; Elaine Patrícia Tavares do Espírito Santo (UFPA - Universidade Federal do Pará) ; Silvia Helena Marques da Silva (IEC - Insituto Evandro Chagas) </td></tr></table><p align=justify><b><font size=2>Abstract</font></b><p align=justify class=tres><font size=2>PCM is a chronic fungal disease caused by the dimorphic fungus <i>Paracoccidioides brasiliensis</i>. Definitive diagnosis is made through the visualization of the fungus on patients clinical samples or the culture of the pathogen, but serological tests are frequently used as a tool for early diagnosis where immunodiffusion is a routine serological test. A latex agglutination test (LA test) was recently evaluated for the detection of anti-<i>P. brasiliensis</i> antibodies, but it has produced cross-reaction with patients samples with aspergillosis (ASP), histoplasmosis (HP) and other non-fungal diseases (NFD). In this study, we evaluated the effect of the inactivation or the pretreatment of PCM samples with low or non-reactivity and cross-reaction in the LA test assay previously performed.Crude exoantigen of -<i>P. brasiliensis</i> was used to coat the latex particles, and the test was realized mixing 25 &#956;L of latex suspension with 25 &#956;L of sera sample inactivated or pretreated. Samples were inactivated by incubation at 56&bull;C/30 min and pretreated by addition of dilution buffer (qualitative test) and incubated at 37&bull;C/30 min.In the pilot test, positive control serum (pool of sera of PCM patients) non-treated, inactivated or pretreated showed pattern 3+, whose titers were 1:16 (non-treated) and 1:8 (inactivated). No reactions were observed with samples of human normal sera. The samples of the previous work tested here were from cases of PCM (a total of 21, where 13 showing a one plus {1+}, and 8 negative), HP (1 showing a 1+), ASP (3 showing of 1+ to 2+), and NFD (11 ranged of 1+ to 3+). After inactivation, 4 PCM samples were negative and 17 were positive ranging from 1+ to 4+ (titers up to 1:64). Among the non-PCM sera, cross-reactivity with HP has been eliminated, however, 2 samples of patients with ASP showed 2+; 6 cases of NFD were reactive ranging from 1+ to 2+. No reactions were observed above 1:4. When the samples were pretreated, 3 PCM samples were negative and 18 were positive ranging from 1+ to 4+. As for the non-PCM sera, reaction of the HP sample was also eliminated, while 2 samples showed ASP 1+; 4 cases of NFD were reactive ranging from 1+ to 2+.Although the number of samples is small, we can conclude that to increase the performance of LA test it is better to use the pretreatment, because the non-specific and false-negative reactions decrease considerably.</font></p><br><b>Keyword: </b>&nbsp;Increased performance, Latex Agglutination test, Paracoccidioidomycosis</td></tr></table></tr></td></table></body></html>