Clinical and laboratory findings in the diagnosis of bacterial pneumonia in children.

Abstract

Paediatric Research Centre,Tampere Univer-sity and University Hospital,Tampere, FinlandTo the Editor:Stolz et al. recently presented their findingson the diagnostic value of symptoms, clinicalsigns and laboratory findings in lower respiratorytract infection (LRTI) in adults [1]. On admis-sion, 243 patients with suspected LRTI weretreated either as procalcitonin (PCT)-guided orbytheclinicalpracticeofthehospital,inbothcasesindependentlyoftheauthors.After treatment twoclinical subgroups were formed: bacterial LRTI(antibiotic treatment, bacterial culture positive inblood, sputum or bronchial samples, n = 32) andself-limiting LRTI (spontaneous improvement,no antibiotics, n = 86). Clinical signs and bloodleukocytes (WBC) were not helpful in distin-guishing between bacterial and self-limitingLRTI cases.The sensitivity of the presence of in-filtrates in chest radiographs, C-reactive protein(CRP) >50 mg/l and PCT >0.1 ng/ml was 97%,94% and 94% respectively. The likelihood ratios(LR+) were not expressed but were possible tocalculate, and were 6.90 (infiltrates), 3.35 (CRP)and 3.35 (PCT).Thus, the presence of infiltrateshad a significant effect (LR+ >5.0), whereas CRP>50 mg/l and PCT >0.1 ng/ml had a moderateeffect (LR+ >3.0) on the pre-test probability ofbacterial LRTI [2]. The authors did not investi-gate whether any combination of the markersmanaged better than single parameters.In our recent study in 101 children withcommunity-acquired pneumonia (CAP), bacte-rial aetiology of infection was assessed by serolog-icalmethods[3].Inaccordancewith theresultsofStolz et al. [1], clinical symptoms and signs, suchas tachypnoea defined as respiratory rate >50breaths/min in children aged 40breaths/min in children aged 1–5 years and >30breaths/min in children aged >6 years (32/81,39%), crackles on auscultation (48/99, 48%), orfever >38 °C (72/101, 71%), >38.5 °C (58/101,57%) or >39 °C (38/101, 38%) were not associ-ated with bacterial aetiology. PCT, which wasused to select patients for antibiotic therapy inthe adult study [1],was associated with the sever-ity of CAP like the need for hospital care andwith the presence of alveolar infiltrates in thechest radiograph, but was not associated withbacterial findings in children [3, 4]. None of thenon-specific laboratory parameters by any cut-off point was able to screen pneumococcal, atyp-ical bacterial and viral aetiology of infection. Bythe combination of CRP >100 mg/L, WBC>15000/ul,PCT >1.0 ng/ml and ESR >65 mm/h,LR+ was 3.0 (sensitivity 36%,specificity 88%) inthe distinction between pneumococcal and viralCAP, and 3.6 (sensitivity 43%, specificity 88%)between atypical and viral CAP. If there was avery high value in one of these four parame-ters (CRP >200 mg/L, WBC >22000/uL, PCT>1.8 ng/ml or ESR >90 mm/h),LR+ for bacterial