Comparison ofa New,RapidEnzyme-Linked Immunosorbent Assay withLatexParticle Agglutination fortheDetection ofHaemophilus inflfuenzae TypebInfections

A new,rapid enzyme-linked immunosorbent assay(ELISA) forthedetection ofpolyribosylribitol phosphate ofHaemophilus influenzae typeb was compared witha commercially available latex particle agglutination (LPA)system(Bactigen; WampoleLaboratories, Cranbury, N.J.). Byadding specimens andtheanti-poly- ribosyIribitol phosphate immunoglobulin-enzyme conjugate tothesolid phase ina single step, itwas possible tocomplete theELISAprocedure in30min.TheELISAwas capable ofdetecting 0.3ng ofpolyribosylribitol phosphate permlincerebrospinal fluid, 0.6ng/ml inurine, and1.2ng/ml inserum;theinvitro sensitivity of LPAinthese bodyfluids was 0.6, 0.3, and0.3ng/ml, respectively. Bothprocedures detected polyribosylribitol phosphate inspecimens from25patients withbacteriologically confirmed H. influenzae typebinfections. The specificity ofELISAappeared tobesuperior tothatofLPA.ELISAwas positive inonly oneofsevenpatients whohada positive LPA testanda clinical illness that was notcompatible withhaemophilus infection. Moreover, fivepatients withbacteriologically confirmed infections duetootherpathogens (Streptococcus pneumoniae type14(twopatients), Neisseria meningitidis groupC,Escherichia coli K100,andStaphylococcus aureus) hadfalse-positive LPAtests; onlytwo(E.coli andS.aureus) were positive byELISA.A total of108 samples from61patients whohadnoevidence ofhaemophilus infections werenegative bybothprocedures. The ELISAisarapid, sensitive, andspecific alterdiative toLPAforthedetection ofhaemophilus polyribosylribitol phosphate. Haemophilus influenzae typebcauses avariety ofserious infections ininfants andyoungchildren, including bacter- emia, meningitis, cellulitis, pericarditis, septic arthritis, pneu- monia, empyema,andepiglottitis. Early treatment iscritical, andantibiotics areoften prescribed empirically because the physician cannot waitadayorlonger fordefinitive culture results. Inaddition, cultures maynotbehelpful because manypediatric patients Arealready taking oralantibiotics wheninvasive haemophilus disease isfirst suspected. More- over,insomeinfections, suchaspneumonia ininfants, culture material isdifficult toobtain. Therefore, there has beenconsiderable interest indeveloping rapid diagnostic tests that candetect thepresence ofhaemophilus infection evenwhenbacteria arenolonger viable orwhenappropriate specimens forculture areunavailable. Mostofthetestsintroduced todatehaverelied on detection ofpolyribosylribit ol