Use of time from fever onset improves the diagnostic accuracy of C-reactive protein in identifying bacterial infections.

OBJECTIVE: To determine whether the input of time from fever onset will change the accuracy of C-reactive protein (CRP) in diagnosing bacterial infections in febrile children. STUDY DESIGN: We performed a prospective observational study on febrile children presenting to the emergency department. The diagnostic performance of CRP at different time points from fever onset was compared using a receiver operating characteristic (ROC) curve. RESULTS: Among 373 patients included, 103 (28%) had bacterial infection. The optimal cut-off for CRP suggesting bacterial infection changed with time from fever onset: 6 mg/dL for >12-24 h of fever; 10.7 and 12.6 mg/dL at >24-48 and >48 h of fever, respectively. The input of time from fever onset improved the area under the ROC curve from 0.83 (95% CI 0.78 to 0.88) for CRP overall to 0.87 (95% CI 0.77 to 0.96) and 0.90 (95% CI 0.84 to 0.97) at >24-48 and >48 h of fever, respectively. Duration of fever mostly affected the ability of CRP to correctly rule out bacterial infections. CRP level of 2 mg/dL obtained at ≤24 h of fever corresponds with a post-test probability for bacterial infection of 10%, whereas the same value obtained >24 h of fever reduces the risk to 2%. CONCLUSIONS: Clinicians should apply different CRP cut-off values depending on whether they are trying to rule in or rule out bacterial infection, but also depending on fever duration at the time of CRP testing.

Leukocyte aggregation-related pseudoleukopenia in pediatrics: a sporadic event or a systematic error?

OBJECTIVE: To determine whether electronic counter-related pseudoleukopenia is a rare phenomenon or a systematic underestimation in children with acute infection/inflammation. METHODS: We have used a simple slide test and image analysis to reveal the number of white blood cells and their degree of aggregation. The number of leukocytes counted by an electronic cell analyzer was divided by the number of cells counted on the slides creating an electronic cell-to-slide leukocyte count ratio. RESULTS: A significant (P < 0.0005) negative (r = -0.314) correlation between the above mentioned ratios and the percent of aggregated leukocytes in the peripheral blood was found in a group of 239 children with various acute infections. Thus elevated leukocyte aggregation is associated with a relatively lower electronic analyzer cell count. CONCLUSIONS: The appearance of aggregated leukocytes in the peripheral blood during acute infections might be associated with pseudoleukopenia. This phenomenon has been extensively described in the adult population and seems to exist in children as well.

Automatic 3-dimensional visualization of peripheral blood slides: a new approach for the detection of infection/inflammation at the point of care.

CONTEXT: The identification and quantitation of the intensity of the acute-phase response at the point of care might be of clinical relevance. OBJECTIVE: To report the possibility of automatic screening of unstained peripheral blood slides by using a 3-dimensional image analysis system. DESIGN: Peripheral venous blood was obtained from children with acute inflammation/infection and examined by an automatic 3-dimensional image analyzer to detect the number of white blood cells as well as to reveal the degree of erythrocyte aggregation, a marker of the humoral phase response. RESULTS: We included 66 children with acute bacterial infections and 59 with nonbacterial inflammation/infection; mean ages of the 2 groups were 4.3 +/- 3.9 years and 4.2 +/- 3.7 years, respectively (P = .91). The percentages of correct classifications based on discriminant analysis in predicting between bacterial and nonbacterial inflammation/infection were 61.3% by using the white blood cell count, 64.5% by using the percentage of granulocytes, 61.6% by using the degree of erythrocyte aggregation, and 59.2% by using the number of leukocytes counted on the unstained slides. The results of the receiver-operated characteristic curve analysis yielded an area under the curve of 0.714 (P < .001) for the number of granulocytes, 0.699 (P < .001) for the white blood cell count, 0.685 (P < .001) for the number of leukocytes on the slides, and 0.685 (P = .001) for the degree of erythrocyte aggregation. The correlation between the number of leukocytes by the electronic cell analyzer and the number of cells counted on the slides was highly significant (r = 0.85, P < .001). CONCLUSIONS: It is feasible to use an automatic 3-dimensional image analyzer to reveal the different intensities of the acute-phase response between a group of children with an acute bacterial infection and another with nonbacterial inflammation/infection. These findings might be relevant for potential application at the point of care.

Telemedicine-based application for the detection of inflammation in pediatrics.

To assess the feasibility of using telemedicine for the diagnosis of inflammation in a pediatric population. The degree of erythrocyte adhesiveness/aggregation and the number of white blood cells on peripheral blood slides were evaluated using an image analysis system and transferred to an operator in a remote location. A highly significant correlation was found between the degrees of erythrocyte adhesiveness/aggregation as well as estimated white blood cell count determined by a remote operator and the objective measurements of both erythrocyte sedimentation rate and white blood cell count. A reasonable estimate of both erythrocyte sedimentation rate and white blood cell count can be obtained by using telemedicine in a group of children with acute infection/inflammation.

Reduced acute phase response to differentiate between viral and bacterial infections in children.

The objective of this study was to document the reduced acute phase response that appears in children with viral as opposed to bacterial infections. The white blood cell count (WBCC), the erythrocyte sedimentation rate (ESR), and leukocyte and erythrocyte adhesiveness/aggregation were determined in 36 children with acute bacterial infection, 29 children with viral infection, and 19 controls. A significant reduced WBCC, ESR, and leukocyte and erythrocyte adhesiveness/aggregation was noted in the children with acute viral infection as opposed to those with bacterial infection: 10,800 +/- 3600 and 20,000 +/- 10,000 cells/cm2, 29 +/- 21 and 53 +/- 35 mm Hg, 23 +/- 9 and 41 +/- 15%, and 3.4 +/- 5.1 and 9.8 +/- 13.6 microns, respectively. The results indicate that a reduced acute phase response can be observed in children with an acute viral infection. This can have diagnostic implications and pathophysiological consequences in terms of less flow impairment in the microcirculation due to less red and white blood cell aggregation.