Febrile infants less than eight weeks old. Predictors of infection

Managing Febrile Infants

The authors hypothesized that sepsis workup recommendations are associated with practice recommendations published during the physician’s residency. The first published recommendations suggesting sepsis workups for nontoxic, young, febrile infants appeared in pediatric journals from 1975-1980 and in family practice journals from 1981-1987. Data are from the Community Tracking Study (3,272 pediatricians and 2,432 family physicians). “Percentage of sepsis workups recommended” was defined by response to a vignette about the percentage of well-appearing 6-week-old children with a fever of 101°F for whom the physician would recommend a sepsis workup. Multivariable regression with piecewise linear functions evaluated workup recommendations by timing of literature recommendations during residency. Pediatricians recommended sepsis workups 81.6% of the time and family physicians 67.7% (p < .001). Increased recommendations occurred among pediatricians who completed residency from 1975-1980 (p < .05) and among family physicians who completed residency from 1981-1987 (p < .005), when specialty-specific journals published recommendations for sepsis workups for febrile infants. The association between publication of sepsis workup recommendations during a physician’s residency and increased sepsis workup recommendations suggests an unrecognized and enduring impact of such publications.

Predicting severe bacterial infections in well-appearing febrile neonates: laboratory markers accuracy and duration of fever

OBJECTIVES

To assess the diagnostic accuracy of white blood cell count (WBC), absolute neutrophil count (ANC), and C-reactive protein (CRP) in detecting severe bacterial infections (SBI) in well-appearing neonates with early onset fever without source (FWS) and in relation to fever duration.

METHODS

An observational study was conducted on previously healthy neonates 7 to 28 days of age, consecutively hospitalized for FWS from less than 12 hours to a tertiary care Pediatric Emergency Department, over a 4-year period. Laboratory markers were obtained upon admission in all patients and repeated 6 to 12 hours from admission in those with normal values on initial determination. Sensitivity, specificity, positive and negative likelihood ratios, and receiver operating characteristic analysis were carried out for primary and repeated laboratory examinations.

RESULTS

Ninety-nine patients were finally studied. SBI was documented in 25 (25.3%) neonates. Areas under receiver operating characteristic curves were 0.78 (95% CI, 0.69-0.86) for CRP, 0.77 (95% CI, 0.67-0.85) for ANC and 0.59 (95% CI, 0.49-0.69) for WBC. Sixty-two patients presented normal laboratory markers on initial determination. Of these, 58 successfully underwent repeated blood examination at >12 hours from fever onset. Five of them had an SBI. The area under curve calculated for repeated laboratory tests showed better values, respectively of 0.99 (95% CI, 0.92-1) for CRP, 0.85 (95% CI, 0.73-0.93) for ANC and 0.79 (95% CI, 0.66-0.88) for WBC.

CONCLUSIONS

In well-appearing neonates with early onset FWS, laboratory markers are more accurate and reliable predictors of SBI when performed after >12 hours of fever duration. ANC and especially CRP resulted better markers than the traditionally recommended WBC.

Hyperthermia as an early sign of intracranial hemorrhage in full-term neonates

BACKGROUND

Intracranial hemorrhage (ICH) in full-term infants is uncommon and is a rare cause of neonatal fever. This study was conducted to estimate the incidences of ICH and fever in a hospital-based population, and to determine if the clinical features of neonatal ICH with and without hyperthermia differ.

METHODS

We selected 315 afebrile neonates who received cranial ultrasonography screening from 2003 to 2004 as the control group, and 153 neonates diagnosed with fever from 1998 to 2004 as the study group. During the same period, 28 full-term neonates with birth weights >2500g and ICH in the first week of life were enrolled retrospectively. They were divided into hyperthermia (n=11) and nonhyperthermia (n=17) groups.

RESULTS

Three babies in the control group and 11 in the study group had ICH; the incidence of ICH in the hyperthermia group was significantly higher (3/315 vs. 11/153; p < 0.001). Compared with the nonhyperthermia group, the hyperthermia group had Less cyanosis (2/11 vs. 10/17; p = 0.04), Less lymphocyte predominance (33.7 vs. 80%; p = 0.032), higher neutrophil/lymphocyte ratio (1.9 vs. 0.3; p = 0.006), higher erythrocyte/leukocyte ratio (425 vs. 79.5; p = 0.05) in cerebrospinal fluid and an increased incidence of subarachnoid hemorrhage accompanied by intracerebral parenchymal hemorrhage (4/11 vs. 0/17; p = 0.016).

CONCLUSION

The incidence of ICH was higher in febrile than in afebrile neonates. ICH presenting with hyperthermia might go unrecognized, because its other symptoms are subtle and a neutrophil predominance in the cerebrospinal fluid might result in a misdiagnosis of meningitis. ICH in the interior brain tended to manifest more commonly as hyperthermia than did ICH in the superficial brain. A cranial image examination should be considered in the evaluation of neonatal fever.

Serious bacterial infections in febrile infants 1 to 90 days old with and without viral infections

OBJECTIVE

The risk of serious bacterial infection (SBI) in febrile infants who are classified as low risk (LR) or high risk (HR) by the Rochester criteria has been established. LR infants average a 1.4% occurrence of SBI, whereas HR infants have an occurrence of 21%. The occurrence of SBI in Rochester LR or HR infants with confirmed viral infections is unknown. The objective of this study was to determine the occurrence of SBI in Rochester LR and HR infants with and without viral infections.

METHODS

All febrile infants who were 90 days or younger and evaluated at Primary Children's Medical Center between December 1996 and June 2002 were eligible. Infants were classified as Rochester LR or HR, and discharge diagnoses were collected. Viral testing for enteroviruses, respiratory viruses, rotavirus, and herpesvirus was performed as indicated by study protocol, clinical presentation, and season of the year. Results of all bacterial cultures were reviewed.

RESULTS

Of 1779 infants enrolled, 1385 (78%) had some form of viral diagnostic testing and 491 (35%) had 1 or more viruses identified. By the Rochester criteria, 456 (33%) infants were classified as LR and 922 (67%) infants as HR. For infants with viral infections, the occurrence of SBI was significantly lower than in infants without a viral infection (4.2% vs 12.3%). Rochester HR virus-positive (HR+) infants had significantly fewer bacterial infections than HR virus-negative (HR-) infants (5.5% vs 16.7%). When compared with HR- infants, HR+ infants were less likely to have bacteremia, urinary tract infection, or soft tissue infections, and HR+ infants had a similar occurrence of bacteremia as LR infants (0.92% vs 1.97%).

CONCLUSIONS

Febrile infants with confirmed viral infections are at lower risk for SBI than those in whom a viral infection is not identified. Viral diagnostic data can positively contribute to the management of febrile infants, especially those who are classified as HR.

Identifying febrile young infants with bacteremia: is the peripheral white blood cell count an accurate screen?

STUDY OBJECTIVE

We estimated the accuracy of the total peripheral WBC count as a screen for bacteremia in febrile young infants.

METHODS

We evaluated, retrospectively, the performance characteristics of linear and nonlinear (U-shaped) logistic models for predicting bacteremia that are based on the total peripheral WBC count. Research subjects were consecutive 0- to 89-day-old infants who had a temperature in triage of greater than or equal to 38 degrees C (> or =100.4 degrees F) and were evaluated for infection at a pediatric emergency department (1993 to 1999). Infants with leukemia were excluded. Areas under the receiver operator characteristic curves (AUC), as well as sensitivity, specificity, interval likelihood ratios, and the corresponding odds of bacteremia predicted at various thresholds of the test, were calculated.

RESULTS

The rate of bacteremia was 1% (38/3,810). The U-shaped model was more accurate (AUC 0.69 versus 0.56); however, no threshold of the total peripheral WBC count had both good sensitivity and specificity. Sensitivity and specificity values were 79% and 5%, respectively, at a peripheral WBC count cutoff of 5,000 cells/mm(3), and 45% and 78%, respectively, at a cutoff of 15,000 cells/mm(3). The odds of bacteremia were not decreased substantially at any cutoff and were increased only modestly at values outside published norms of the test.

CONCLUSION

The total peripheral WBC count is an inaccurate screen for bacteremia in febrile young infants; thus, decisions to obtain blood cultures should not rely on this test.

Clinical utility of the band count

Enumeration of band neutrophils has a long clinical tradition as a diagnostic test for bacterial infection. Yet, the band count is a nonspecific, inaccurate, and imprecise laboratory test. Review of the literature provides little support for the clinical utility of the band count in patients greater than 3 months of age. The white blood cell count and the automated absolute neutrophil count are better diagnostic tests for adults and most children. Absolute numbers of bands are required for the Rochester criteria, a diagnostic algorithm for acutely ill, febrile children less than 3 months of age. No studies, however, assess the independent contribution of bands to the performance of the algorithm, or the use of the automated total neutrophil count as a replacement for the band count. Band counts also are required to calculate an immature to total neutrophil ratio (I:T ratio), an index widely used to aid in the diagnosis of neonatal sepsis. Studies, however, show a wide range of sensitivity and specificity for the I:T ratio, indicating variable performance. In the near future, rapid analysis of inflammatory factors, adhesion molecules, cytokines, neutrophil surface antigens, or even bacterial DNA may be superior alternative tests for the early diagnosis of sepsis.

Management of fever without source in infants and children

Twenty percent of febrile children have fever without an apparent source of infection after history and physical examination. Of these, a small proportion may have an occult bacterial infection, including bacteremia, urinary tract infection (UTI), occult pneumonia, or, rarely, early bacterial meningitis. Febrile infants and young children have, by tradition, been arbitrarily assigned to different management strategies by age group: neonates (birth to 28 days), young infants (29 to 90 days), and older infants and young children (3 to 36 months). Infants younger than 3 months are often managed by using low-risk criteria, such as the Rochester Criteria or Philadelphia Criteria. The purpose of these criteria is to reduce the number of infants hospitalized unnecessarily and to identify infants who may be managed as outpatients by using clinical and laboratory criteria. In children with fever without source (FWS), occult UTIs occur in 3% to 4% of boys younger than 1 year and 8% to 9% of girls younger than 2 years of age. Most UTIs in boys occur in those who are uncircumcised. Occult pneumococcal bacteremia occurs in approximately 3% of children younger than 3 years with FWS with a temperature of 39.0 degrees C (102.2 degrees F) or greater and in approximately 10% of children with FWS with a temperature of 39.5 degrees C (103.1 degrees F) or greater and a WBC count of 15, 000/mm(3) or greater. The risk of a child with occult pneumococcal bacteremia later having meningitis is approximately 3%. The new conjugate pneumococcal vaccine (7 serogroups) has an efficacy of 90% for reducing invasive infections of Streptococcus pneumoniae. The widespread use of this vaccine will make the use of WBC counts and blood cultures and empiric antibiotic treatment of children with FWS who have received this vaccine obsolete.

Urinary tract infection in febrile infants younger than eight weeks of Age

OBJECTIVE

To assess the usefulness of laboratory parameters, including peripheral white blood cell (WBC) count, C-reactive protein (CRP) concentration, erythrocyte sedimentation rate (ESR), and microscopic urinalysis (UA), for identifying febrile infants younger than 8 weeks of age at risk for urinary tract infection (UTI), and comparison of standard UA and hemocytometer WBC counts for predicting the presence of UTI.

METHODS

A total of 162 febrile children <8 weeks of age were enrolled in this prospective study. All underwent clinical evaluation and laboratory investigation, including WBC count and differential; ESR; CRP; blood culture; a lumbar puncture for cell count and differential, glucose level, protein level, Gram stain, and culture; and a UA and urine culture. All urine specimens were obtained by suprapubic aspiration and microscopically analyzed with standard UA as well as with hemocytometer WBC counts. Quantitative urine cultures were performed. Sensitivity, specificity, accuracy, likelihood ratios, and receiver operating characteristic (ROC) curves were determined for each of the screening tests.

RESULTS

There were 22 positive urine culture results of at least 100 colony-forming unit/mL. Eighteen of these 22 patients were males, and all were uncircumcised. There were significant differences for pyuria >/=5 WBCs/hpf, pyuria >/=10 WBC/microL, CRP >20 mg/L, and ESR >30 mm/hour between culture-positive and culture-negative groups (P <.05). The ROC area for hemocytometer WBC count, standard UA, peripheral WBC count, ESR, and CRP concentration were.909 +/-.045,.791 +/-.065,.544 +/-.074,. 787 +/-.060, and.822 +/-.036, respectively. The ROC curve analysis indicates that the CRP, ESR, and standard UA were powerful but imperfect tools with which to discriminate for UTI in potentially infected neonates. Hemocytometer WBC counts had the highest sensitivity, specificity, accuracy, and likelihood ratios for identifying very young infants with positive urine culture results. For all assessments, hemocytometer WBC counts were significantly different, compared with the standard urinalysis. ESR, CRP, and peripheral WBC counts were not helpful in identifying UTI in febrile infants.

CONCLUSION

UTI had a prevalence of 13.6% in febrile infants <8 weeks of age. The CRP, ESR, and standard UA were imperfect tools in discriminating for UTI, and the sensitivity of these laboratory parameters was relatively low. Hemocytometer WBC count was a significantly better predictor of UTI in febrile infants.

Predictors of physician compliance with a published guideline on management of febrile infants

BACKGROUND

Previous studies have demonstrated clinicians' poor compliance with published management strategies and protocols, but the reasons why physicians often choose to vary their management of the febrile infant from published guidelines are poorly understood.

OBJECTIVE

We conducted a study of physicians to learn more about the issues that influence their decisions in the management of febrile infants.

METHODS

A survey study of pediatricians, emergency physicians and family physicians randomly selected from a list of licensed physicians in the United States. Chi square and Kruskal-Wallis tests were used to measure differences in responses by specialty. Odds ratios from logistic regression were used to measure differences in compliance with a recently published guideline.

RESULTS

We received 193 completed surveys from pediatricians, 177 from emergency physicians and 104 from family physicians. After controlling for other variables, odds for compliance with a recently published guideline were higher for pediatricians [odds ratio (OR) = 9.13] and emergency physicians (OR = 2.5) than for family physicians (P < 0.001). Factors associated with decreased odds of compliance included more years since graduation from medical school (OR = 0.93), a higher proportion of office visits by children < 1 year of age (OR = 0.97) and increased comfort diagnosing serious bacterial illness (OR = 0.35). Factors associated with increased odds of compliance included a higher perceived likelihood of serious bacterial illness in febrile infants (OR = 1.01) and better reported knowledge of the recently published guideline (OR = 2.01).

CONCLUSIONS

We found that specialty as well as other factors were associated with physician compliance with a recently published guideline. This information may facilitate guideline development and implementation by providing a better understanding of what motivates physicians in their clinical decision making.

Evaluation of the infant with fever without source: an evidence based approach

The infant with fever without an obvious source upon physical examination offers a challenging clinical problem. A combination of detailed history, physical examination, and selected laboratory tests allows the clinician to discern which infants are at lower risk for bacterial illness. Implications for management and future research are discussed herein.

Managing fever in infants and toddlers: toward a standard of care

Fever in infants and toddlers can portend a serious bacterial illness requiring a prompt medical response. When dealing with a febrile child between 1 and 36 months of age, physicians should consider toxicity, focal infections, age, and the results of a sepsis workup and then use a strategy based on the Rochester criteria to assess whether the patient is at low risk for a serious bacterial illness. On the basis of that determination, a plan for inpatient or outpatient management can be selected. Variations in treatment can reasonably be based on clinical judgment and physician and parent preferences.

Initial approach to the infant younger than 2 months of age who presents with fever

Fever is common in infants presenting to their physicians for evaluation. Infants younger than 2 months of age are at increased risk of SBI because of their exposure to different pathogens and because of their immature immune systems. The bacteria that may infect them include E coli, group B Streptococcus, and L monocytogenes, as well as Pneumococcus, Neisseria meningitidis, S aureus, and H influenzae. They are also susceptible to viruses, parasites, and fungi. Clinical characteristics associated with increased risk of SBI have been identified. Infants who are ill-appearing, have abnormal hemograms or urinalyses, or have evidence of bacterial infection on physical examination are at higher risk. There has been an association of very high fever with SBI, although this has been inconclusive. Clinical judgment is important, although not always completely reliable in ruling out SBI. Young infants with fever should be evaluated with a thorough history, physical examination, and selected laboratory studies. Those younger than 29 days of age should usually be admitted for observation and parenteral antibiotics. Infants from 29 to 60 days of age may be evaluated carefully and considered for outpatient management, either with or without antibiotics.

Practice guideline for the management of infants and children 0 to 36 months of age with fever without source. Agency for Health Care Policy and Research

STUDY OBJECTIVE

To develop guidelines for the care of infants and children from birth to 36 months of age with fever without source.

PARTICIPANTS AND SETTING

An expert panel of senior academic faculty with expertise in pediatrics and infectious diseases or emergency medicine.

DESIGN AND INTERVENTION

A comprehensive literature search was used to identify all publications pertinent to the management of the febrile child. When appropriate, meta-analysis was used to combine the results of multiple studies. One or more specific management strategies were proposed for each of the decision nodes in draft management algorithms. The draft algorithms, selected publications, and the meta-analyses were provided to the panel, which determined the final guidelines using the modified Delphi technique.

RESULTS

All toxic-appearing infants and children and all febrile infants less than 28 days of age should be hospitalized for parenteral antibiotic therapy. Febrile infants 28 to 90 days of age defined at low risk by specific clinical and laboratory criteria may be managed as outpatients if close follow-up is assured. Older children with fever less than 39.0 C without source need no laboratory tests or antibiotics. Children 3 to 36 months of age with fever of 39.0 C or more and whose WBC count is 15,000/mm3 or more should have a blood culture and be treated with antibiotics pending culture results. Urine cultures should be obtained from all boys 6 months of age or less and all girls 2 years of age or less who are treated with antibiotics.

CONCLUSION

These guidelines do not eliminate all risk or strictly confine antibiotic treatment to children likely to have occult bacteremia. Physicians may individualize therapy based on clinical circumstances or adopt a variation of these guidelines based on a different interpretation of the evidence.

Selecting diagnostic tests to identify febrile infants less than 3 months of age as being at low risk for serious bacterial infection: a scientific overview

PURPOSE

To select diagnostic tests that confidently identify febrile infants less than 3 months of age seen at an outpatient facility as being at low risk for serious bacterial infection (SBI).

DATA IDENTIFICATION

An English-language literature search employing MEDLINE (1966 to 1991), Science Citation Index (1977 to 1991) using key citations, bibliographic reviews of primary research and review articles, and correspondence with authors of recent articles.

STUDY SELECTION

After independent review by two observers, 10 of 333 originally identified titles were selected on the basis of prespecified selection criteria.

DATA EXTRACTION

Two observers independently assessed studies by using explicit methodologic criteria for evaluating the quality of studies dealing with diagnostic tests. One reviewer extracted all the data from the articles; the second reviewer checked these data for accuracy.

RESULTS OF DATA ANALYSIS

On the basis of prespecified criteria, results were pooled from two studies that used the Rochester criteria, had high methodologic validity, and did not have significant heterogeneity (p = 0.32, Breslow-Day test), to give an estimate of the best negative likelihood ratio (95% confidence interval) for SBI = 0.03; 0 to 0.23).

CONCLUSION

The negative likelihood ratio of 0.03 allowed us to conclude that after the Rochester criteria for low risk of SBI have been satisfied, the probability of SBI in a febrile infant less than 3 months of age drops from a baseline rate of 7% (or 1 in 14 infants) to 0.2% (or 1 in 500). An expectant approach in these low-risk infants is therefore a reasonable choice.