Biochemical tests cannot differentiate between tonsillar and middle ear-derived infections.

INTRODUCTION: Infection markers are appreciated supplements in the clinical diagnosis of ear, nose and throat (ENT) infections. We aimed to examine the differential diagnostic usefulness of C-reactive protein (CRP), white blood cell count (WBC) and absolute neutrophil count (ANC) according to severity of middle ear and tonsillar infections.
MATERIAL AND METHODS: This was a retrospective study including all patients admitted to the ENT Department, Aarhus University Hospital, from January 2001 to December 2008 and diagnosed with acute otitis media, mastoidismus, acute mastoiditis, acute tonsillitis, peritonsillar abscess, parapharyngeal abscess and necrotizing fasciitis.
RESULTS: A total of 1,773 patients were included. Between the tonsil subgroups, significant differences were found in CRP (p < 0.001), WBC (p < 0.001) and ANC (p < 0.001) levels. However, sensitivities and specificities related to differential diagnostics were low. In the middle ear group, no differences in CRP (p = 0.84), WBC (p = 0.46), and ANC (p = 0.72) levels were found. The number of CRP levels above the reference value was significantly higher than the corresponding number of WBC and ANC levels. A trend (non-significant) was found towards lower parameter levels in acute tonsillitis and peritonsillar abscess patients who grew Staphylococcus aureus compared with patients infected with other bacteria.
CONCLUSION: CRP and ANC levels were related to severity of tonsillar-derived infections, but no such relation was found in infections with middle ear origin. None of the infection markers studied were useful for differential diagnostics. FUNDING: not relevant. TRIAL REGISTRATION: not relevant.