Infection markers have limited role in differential diagnosis
medwireNews: Diagnostic tests, such as for C-reactive protein (CRP) and white blood cell count (WBC), cannot effectively discriminate between middle ear and tonsillar infections, say the authors of a study involving over 1500 patients.
"We observed a tendency towards higher levels of infection parameters in severe and extensive infections (parapharyngeal abscess and necrotizing fasciitis) than in less extensive tonsillar infections (acute tonsillitis and peritonsillar abscess)," say Ann Marlene Gram Christensen (Aarhus University Hospital, Denmark) and colleagues.
"However, the infection parameters could not stand alone in the differential diagnosis-making as the sensitivities and specificities were low."
The study included 1773 patients admitted to hospital between 2001 and 2008 with tonsil infection (in increasing order of severity): acute tonsillitis (n=453), peritonsillar abscess (n=1066), parapharyngeal abscess (n=45), and necrotizing fasciitis (n=34); or middle ear infection: acute otitis media (n=46), mastoidismus (n=75), and acute mastoiditis (n=54).
As reported in the Danish Medical Journal, there were significant differences in levels of CRP, WBC, and absolute neutrophil count (ANC) according to tonsil infection severity. For example, the mean CRP level was 297.6 mg/L in patients with necrotizing fasciitis compared with 123.3 mg/L in patients with acute tonsillitis, while the corresponding ANC values were 12.8 x 109/L and 10.1 x 109/L, respectively.
However, the sensitivities and specificities in relation to differential diagnosis were low at 50-80% and 44-63% for CRP, 61-80% and 47-54% for WBC, and 60-77% and 44-58% for ANC, respectively.
The authors also note that levels of CRP were higher in patients with acute tonsillitis than patients with peritonsillar abscess, despite CRP being routinely used in the diagnosis of suspected abscess.
Furthermore, there was no significant association between any of the markers and disease severity among patients with middle ear infection.
And, patients frequently had discordant parameters between markers. For example, 11% to 23% of patients in the tonsil infection group had either elevated CRP and normal WBC levels, or normal CRP and elevated WBC levels, and 16% to 23% of patients with middle ear infection had only one elevated parameter.
Therefore, "none of the infection markers studied was useful for differential diagnostics," Christensen and colleagues conclude.
They suggest that procalcitonin could be explored in future as an alternative differential diagnostic marker.
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By Kirsty Oswald, medwireNews Reporter