Prof. Hee-Joo, Lee May, 11, 2009

Introduction Dx of pneumococcal infection : –Culture methods –Nucleic acid amplification –Ag detection BinaxNow S.pneumoniae : –C polysaccharide Ag in urine –Good sensitivity –Very specific in adult pts with invasive pneumococcal infection PCR methods –Good sensitivity, poor specificity for sputum –Blood : excellent specificity, poor sensitivity –Author have devised dual-PCR (lytA, ply)

Aim Compare the BinaxNow urinary Ag test t o the dual-PCR testing protocole on ED TA blood samples for the Dx of serious S. p neumoniae infections

Materials & Methods (I) Three groups –Pneumococcal bacteremia mostly with CAP –CAP with – bl culture –Control with other community acquired septicemia without pneumonia

Materials & Methods (II) Pneumonia : –Acute illness with infiltrates on chest radiogra ph –+ at least 2 : fever, cough, dyspnea, pleuritic c hest pain Bl culture – pneumonia : –Divided by chest radiograph, WBC, CRP Likely pneumococcal infection Possible pneumococcal infection group

Materials & Methods (III) Binax Now pneumonia Ag test Pneumolysin-targeted TagMan assay & autol ysin-targeted Light cycler assay on EDTA blo od samples Student’s t test or analysis of variance Mann-Whitney or Wilcoxon two sample test Proportion were compared by the chi-square with yeates’ correction

Results 332 adult cases –82 : pneumococcal bacteremia 23 : pneumonia – 59 : pneumonia + –149 : nonbacteremic CAP –101 : control pts 94 : other organism septicemia, 7 : other organism pneumonia

Discussion Sputum or other respiratory PCR : good rates of positivity but poor specificity Blood PCR : excellent specificity but relative poor specificity Dual PCR protocol : sensitivity increase (52% ) –Less sensitive than Binax urinary Ag test (86%) –Specificity is similar

Low sensitivity of dual-PCR protocol –Partly due to sample processing procedure Selection bias in the subgroups of non-ba cteremic pneumonia makes it difficult to c ompare studies & to determine accurately what proportion of all CAP is caused by th e pneumococcus.

Compared to dual-target PCR, the BinaxNow S. pneumoniae urinary Ag test is much better test for the early Dx of bacteremic pneumoco ccal infections in adults. The Binax Now test also performs better in ca se of nonbacteremic CAP and will more accur ately detect thoses cases caused by S. pneu moniae.

Streptococcus pneumoniae Optochin test Gram stain

How the Antigen gets in the Urine 1.S. pneumoniae in lung die 2.Bacteria break-down 3.C-polysaccharide (Ag) passes into the bloodstream 4.C-polysaccharide (Ag) is processed by the kidney and concentrated 5.C-polysaccharide (Ag) is excreted in the urine

MethodsSample Type SensitivitySpecificity Time Binax NOW ® Urine86% 94%15 min Blood CultureBlood10-30% >95%24-48 hrs Sputum CultureSputum 44-60% 50-85%24-48 hrs Sputum Gram StainSputum31-60% 50-85%15 min Comparison of S. pneumoniae test methods