Neutrophil CD64 expression: a sensitive diagnostic marker for late-onset nosocomial infection in very low birthweight infants

Hematologic profile of sepsis in neonates: neutrophil CD64 as a diagnostic marker

OBJECTIVE

The goal was to determine the utility of neutrophil CD64 as a diagnostic marker for sepsis in neonates.

METHODS

A prospective study that enrolled consecutive infants with suspected sepsis was performed. Complete blood count with differential, blood culture, and CD64 index measurement were performed, and neutrophil CD64 indices were correlated with the diagnoses of confirmed and suspected sepsis.

RESULTS

There were 293 episodes of sepsis evaluations for 163 infants. Infants with sepsis episodes (confirmed or suspected; n = 40) were of greater gestational age (34.7 +/- 0.9 weeks), compared with those (n = 123) with no sepsis (32.6 +/- 0.5 weeks), but had similar birth weights (2325 +/- 200 vs 1969 +/- 94 g) and Apgar scores at 1 and 5 minutes. There was no difference in the duration of hospitalization for the 2 groups. As expected, the hematologic profiles of sepsis episodes (n = 128) were characterized by higher white blood cell counts, absolute neutrophil counts, absolute band counts, and immature/total neutrophil ratios but lower platelet counts. Sepsis episodes had higher neutrophil CD64 indices (5.61 +/- 0.85 vs 2.63 +/- 0.20). For all sepsis episodes, the CD64 index had an area under the curve, in receiver operating characteristic analysis, of 0.74; with a cutoff value of 2.30, the CD64 index in combination with the absolute neutrophil count had the highest negative predictive value (93%) for ruling out sepsis and 95% sensitivity for diagnosing sepsis. For culture-positive sepsis episodes, the CD64 index had the highest area under the curve (0.852) of all hematologic variables, with a sensitivity of 80% and a specificity of 79%, with a cutoff value of 4.02.

CONCLUSIONS

Neutrophil CD64 is a highly sensitive marker for neonatal sepsis. Prospective studies incorporating CD64 into a sepsis scoring system are warranted.

Classifying esophageal motility by pressure topography characteristics: a study of 400 patients and 75 controls

AIM

This study aimed to devise a scheme for the systematic analysis of esophageal high-resolution manometry (HRM) studies displayed using topographic plotting.

METHODS

A total of 400 patients and 75 control subjects were studied with a 36-channel HRM assembly. Studies were analyzed in a stepwise fashion for: (a) the adequacy of deglutitive esophagogastric junction (EGJ) relaxation, (b) the presence and propagation characteristics of distal esophageal persitalsis, and (c) an integral of the magnitude and span of the distal esophageal contraction.

RESULTS

Two strengths of pressure topography plots compared to conventional manometric recordings were: (a) the ability to delineate the spatial limits, vigor, and integrity of individual contractile segments along the esophagus, and (b) the ability to distinguish between loci of compartmentalized intraesophageal pressurization and rapidly propagated contractions. Making these distinctions objectified the identification of distal esophageal spasm (DES), vigorous achalasia, functional obstruction, and nutcracker esophagus subtypes. Applying these distinctions made the diagnosis of spastic disorders quite rare: (a) DES in 1.5% patients, (b) vigorous achalasia in 1.5%, and (c) a newly defined entity, spastic nutcracker, in 1.5%.

CONCLUSIONS

We developed a systematic approach to analyzing esophageal motility using HRM and pressure topography plots. The resultant scheme is consistent with conventional classifications with the caveats that: (a) hypercontractile conditions are more specifically defined, (b) distinctions are made between rapidly propagated contractions and compartmentalized esophageal pressurization, and (c) there is no "nonspecific esophageal motor disorder" classification. We expect that pressure topography analysis, with its well-defined functional implications, will prove valuable in the clinical management of esophageal motility disorders.

Simultaneous quantitative analysis of FcgammaRI (CD64) expression on neutrophils and monocytes: a new, improved way to detect infections

We performed simultaneous quantitative flow cytometric analysis of neutrophil and monocyte FcgammaRI (CD64) in 289 hospitalized febrile patients. Microbiological evaluation or clinical diagnosis confirmed bacterial (n=89) or viral (n=46) infection in 135 patients. Patient data were compared with data from 60 healthy controls. The average number of FcgammaRI on the surfaces of both neutrophils and monocytes was significantly increased in patients with febrile viral and bacterial infections, compared to healthy controls. Furthermore, we describe a novel marker of febrile infection, designated 'CD64 score point', which incorporates the quantitative analysis of FcgammaRI expressed on both neutrophils and monocytes, with 94% sensitivity and 98% specificity in distinguishing between febrile infections and healthy controls. By contrast, analysis of FcgammaRI expression on neutrophils and monocytes displayed poor sensitivity (73% and 52%) and specificity (65% and 52%) in distinguishing between bacterial and viral infections, and the levels did not differ significantly between systemic (sepsis), local, and clinically diagnosed bacterial infections. In summary, our results clearly show that the increased number of FcgammaRI on neutrophils and monocytes is a useful marker of febrile infection, but cannot be applied for differential diagnosis between bacterial and viral infections or between systemic and local bacterial infections.

Distinction between bacterial and viral infections

PURPOSE OF REVIEW

To commence proper treatment as rapidly as possible and to reduce unnecessary antibiotic treatments, timely knowledge of whether the infection is bacterial or viral in origin would be beneficial for the clinician. As a reliable prediction of the causative agent of bacterial infection is not possible based on clinical features, there is an ongoing need for sensitive and specific markers of bacterial infection.

RECENT FINDINGS

The most common differential diagnosis methods are reviewed here. It is also demonstrated that the measurement of the expression of complement receptors, particularly CR1 (CD35), on neutrophils can be a useful preliminary test to differentiate between bacterial and viral infections. In addition, a novel marker of local and systemic bacterial infections designated 'clinical infection score (CIS) point', which incorporates quantitative analysis of complement receptors on neutrophils and standard clinical laboratory data and displays 98% sensitivity and 97% specificity in distinguishing between bacterial and viral infections, is presented.

SUMMARY

We conclude that the diagnostic yield of measured individual variables in distinguishing between bacterial and viral infections increases upon combination.

Neutrophil CD64 expression is associated with severity and prognosis of disseminated intravascular coagulation

INTRODUCTION

Although neutrophil can be activated by microcirculatory disturbances in DIC, its relation with the severity and prognosis of DIC has not been elucidated. We investigated the relationship between neutrophil activation and DIC severity and determined the prognostic value of neutrophil activation markers in patients with DIC.

MATERIALS AND METHODS

We measured two neutrophil activation markers, neutrophil CD64 expression and plasma neutrophil elastase, in 94 patients with suspected DIC and 55 healthy controls. Neutrophil CD64 expression and plasma neutrophil elastase were measured using CD64 quantitation kit, and PMN Elastase enzyme immunoassay kit.

RESULTS

Neutrophil CD64 expression and plasma neutrophil elastase level were significantly increased in patients with overt and non-overt DIC compared to normal controls (P<0.001, each). Neutrophil CD64 expression showed a significant linear trend of increase with increasing DIC score (P<0.001). In DIC patients, significant differences were observed between those with and without infection both in overt (P=0.003) and non-overt DIC (P=0.004). Neutrophil CD64 expression was significantly increased in 28-day non-survival group compared to survival group in both overt (P<0.001) and non-overt DIC (P=0.032). The 28-day survival rate showed a stronger association with the neutrophil CD64 expression (P<0.001) than with DIC score (P=0.028) or plasma neutrophil elastase level (P=0.246).

CONCLUSIONS

Neutrophil CD64 expression is significantly correlated with DIC severity and has a good predictive value for the 28-day mortality in patients suspected of having DIC. Neutrophil CD64 expression might be useful in monitoring the disease course and in predicting mortality in DIC patients.

Biomarkers in neonatal infection

Infected newborn infants are often difficult to differentiate from patients suffering from noninfective diseases. Whilst delaying treatment with antibiotics of infected infants may be fatal, widespread indiscriminate use in all cases with suspected bacterial infection could lead to both drug-induced complications and the development of multidrug-resistant organisms. Conventional biomarkers, such as blood cell counts and morphology, have serious limitations. Investigators in this area of research have, therefore, made strenuous efforts to discover more reliable biomarkers with superior diagnostic utilities and clinically relevant characteristics to help neonatal clinicians differentiate between infected and noninfected infants. The major classes of biomarkers in neonatal infection of recent interest will be discussed, including: acute phase reactants, cytokines, chemokines and leukocyte surface antigens. The application of these biomarkers to derive prognostic information useful to neonatal clinicians will also be considered.

Application of clinical proteomics in diagnosis and management of trauma patients

Poly-trauma remains a medical entity with major implications, for patient's morbidity, mortality and healthcare economics. Advances in molecular medicine have improved diagnostic techniques in detecting devastating complication after major trauma. Patients at high risk of multiple organ dysfunction syndrome (MODS) or adult respiratory distress syndrome (ARDS), could be identified early, monitored and treated. Proteomics is the systematic evaluation of proteins produced by the cell under normal or pathological circumstances. Investigating protein production will allow us to identify and modify disease natural history and treatment. In this review, we summarise the proteomic methods currently applied in trauma research.

IP-10 is an early diagnostic marker for identification of late-onset bacterial infection in preterm infants

Very low birth weight (VLBW) infants with suspected late-onset infection requiring sepsis screening were enrolled in a prospective study to evaluate the diagnostic utilities of a comprehensive panel of key chemokines and cytokines, both individually and in combination, to identify diagnostic markers for early recognition of bacterial sepsis and necrotizing enterocolitis (NEC). Plasma chemokines interleukin (IL)-8, interferon-gamma-inducible protein 10 (IP-10), monokine induced by interferon-gamma (MIG), monocyte chemoattractant protein 1 (MCP-1), growth-related oncogene-alpha (GRO-alpha), and regulated upon activation of normal T cell expressed and secreted (RANTES) and cytokines IL-1beta, IL-6, IL-10, IL-12p70, and tumor necrosis factor alpha (TNF-alpha) were measured at the onset of sepsis (0 h) and 24 h later. Of 155 suspected infection episodes, 44 were classified as infected. Concentrations of all studied inflammatory mediators (except IL-1beta and RANTES) were significantly higher in the infected than in the noninfected group at 0 h, but the levels decreased precipitously by 24 h. IP-10 with a plasma cutoff concentration > or = 1250 pg/mL could identify all septicemic and NEC cases and had the highest overall sensitivity (93%) and specificity (89%) at 0 h. We conclude that preterm infants have the ability to induce a robust chemokine and cytokine response during sepsis, and IP-10 is a sensitive early marker of infection.

Neutrophil CD64 expression and serum IL-8: Sensitive early markers of severity and outcome in sepsis

The aim of the present study was to investigate which biomarker/s reliably assess severity and mortality early in the sepsis process. In 47 critically-ill patients within the 24h of septic onset, Interleukins (IL)-8, -1beta, -6, -10, and -12p70, tumor necrosis factor-alpha (TNF-alpha), procalcitonin (PCT) and C-reactive protein (CRP) were measured in serum. Additionally, CD64 expression was measured in neutrophils. In early sepsis, neutrophil CD64 expression and IL-8 levels are the only biomarkers that increased with sepsis severity, differentiating disease stages: sepsis, severe sepsis and septic shock (p<0.001). The biomarkers that best evaluate the severity of sepsis (via APACHE II) were CD64, IL-8 and IL-6 (p<0.01), and the severity of organ failure (via SOFA) were CD64 and IL-8 (p<0.01). CD64 expression and IL-8 levels were associated with mortality within 28-days (OR=1.3, p=0.01 for CD64 and OR=1.26, p=0.024 for IL-8 by logistic regression analysis) and ROC curve analysis showed high sensitivity and specificity for predicting sepsis stages and the 28 day mortality. We conclude that there is an early increase of neutrophil CD64 expression and IL-8 levels during sepsis. Based on this single measurement it is possible to reliably assess the stage, detect the severity and predict the 28-day mortality of sepsis.

Quantitative analysis of complement receptors, CR1 (CD35) and CR3 (CD11b), on neutrophils improves distinction between bacterial and viral infections in febrile patients: Comparison with standard clinical laboratory data

There is an ongoing need for sensitive and specific markers of bacterial infection. In this prospective study, standard clinical laboratory data (neutrophil count, serum C reactive protein level, erythrocyte sedimentation rate) and quantitative flow cytometric analysis of neutrophil complement receptors, CR1 and CR3, were obtained from 289 hospitalized febrile patients. After microbiological confirmation or clinical diagnosis, 135 patients were found to have either bacterial (n = 89) or viral (n = 46) infection. The patient data was compared to 60 healthy controls. In bacterial infections, all measured variables were significantly increased, particularly the average amounts of CR1 and CR3 on neutrophils were over three-fold and two-fold higher, respectively, compared to viral infections and controls. We described a novel marker of local and systemic bacterial infections designated 'clinical infection score (CIS) point', which incorporates quantitative analysis of complement receptors on neutrophils and standard clinical laboratory data. CIS point varied between 0 and 8, and displayed 98% sensitivity and 97% specificity in distinguishing between bacterial and viral infections [average (S.D.); CIS points: 6.2 (1.7) vs. 0.6 (1.0); p < 0.001]. These findings suggest that the proposed CIS-based diagnostic test could potentially assist physicians in deciding whether antibiotic treatment is necessary.

Early Prediction of Sepsis-Induced Disseminated Intravascular Coagulation with Interleukin-10, Interleukin-6, and RANTES in Preterm Infants

Background: The progression to disseminated intravascular coagulation (DIC) in infected very low birth weight (VLBW; &lt;1500 g) infants is difficult to predict with precision at the onset of sepsis. We investigated the immunologic profiles of preterm infants with sepsis, using chemokine and cytokine measurements to predict the development of sepsis-induced DIC at the onset of infection.

Methods: We measured a panel of chemokines and cytokines at 0 and 24 h after clinical presentation in VLBW infants with suspected infection requiring full sepsis screening. The chemokines measured were interleukin (IL)-8, interferon-γ-inducible protein-10 (IP-10), monokine induced by interferon-γ, monocyte chemoattractant protein-1, and regulated upon activation normal T-cell expressed and secreted (RANTES), and the cytokines were IL-6, IL-10, and tumor necrosis factor-α.

Results: Of 195 episodes of suspected clinical sepsis investigated, 62 were culture-confirmed septicemia or necrotizing enterocolitis (28 of these infants developed DIC), 22 were culture-negative clinical infections, and 111 involved noninfected episodes. All studied inflammatory mediators except RANTES showed significantly greater up-regulation in culture-positive infected infants than in noninfected infants at 0 and 24 h, whereas RANTES showed significant down-regulation. The model that used plasma IL-10 (&gt;208 ng/L), IL-6 (&gt;168 ng/L), and RANTES (&lt;3110 ng/L) at 0 h had sensitivity, specificity, and positive and negative predictive values of 100%, 97%, 85%, and 100%, respectively, for identifying infected patients who subsequently developed DIC.

Conclusions: IL-10, IL-6, and RANTES measured at clinical presentation sensitively and accurately predicted the development of DIC in severely infected infants. This information could be vital for early and effective treatment of neonatal sepsis.

Neutrophil CD64 is an improved indicator of infection or sepsis in emergency department patients

CONTEXT

Sepsis, affecting millions of individuals annually with an associated high mortality rate, is among the top 10 causes of death. In addition, improvements in diagnostic tests for detecting and monitoring sepsis and infection have been limited in the last 25 years. Neutrophil CD64 expression has been proposed as an improved diagnostic test for the evaluation of infection and sepsis.

OBJECTIVE

To evaluate the diagnostic performance of a quantitative flow cytometric assay for leukocyte CD64 expression in comparison with the standard tests for infection/sepsis in an ambulatory care setting.

DESIGN

Prospective analysis of 100 blood samples from patients from an emergency department setting in a 965-bed tertiary care suburban community hospital was performed for neutrophil CD64 expression, C-reactive protein, erythrocyte sedimentation rate, and complete blood count. The laboratory findings were compared with a clinical score for the likelihood of infection/sepsis, which was obtained by a blinded retrospective chart review.

RESULTS

The diagnostic performance, as gauged by the clinical score, varied with neutrophil CD64 (sensitivity 87.9%, specificity 71.2%, efficiency 76.8%) and outperformed C-reactive protein (sensitivity 88.2%, specificity 59.4%, efficiency 69.4%), absolute neutrophil count (sensitivity 60.0%, specificity 50.8%, efficiency 53.8%), myeloid left shift (sensitivity 68.2%, specificity 76.3%, efficiency 73.3%), and sedimentation rate (sensitivity 50.0%, specificity 65.5%, efficiency 61.0%).

CONCLUSION

Neutrophil CD64 expression quantitation provides improved diagnostic detection of infection/sepsis compared with the standard diagnostic tests used in current medical practice.

Diagnostic markers for neonatal sepsis

PURPOSE OF REVIEW

To review the current evidence on the use of infection markers for diagnostic evaluation of sepsis in neonates.

RECENT FINDINGS

Recent research in immunology has led to the discovery of cell surface antigens, chemokines, cytokines and acute phase proteins that can potentially be used to 'rule in' or 'rule out' sepsis. The diagnostic utilities of key inflammatory mediators, including CD11b, CD64, interleukin-6 and interleukin-8, are promising and likely to become increasingly used as markers of infection for both diagnostic and prognostic purposes.

SUMMARY

Serial measurements and use of combinations of markers have been reported to improve sensitivity and negative predictive value of these tests. Current markers are not infallible, however, and do not permit neonatologists to withhold antibiotics in sick infants with suspected infection. Thus, many have emerged as useful indicators for early discontinuation of unnecessary antimicrobial therapy. Some infection markers are also useful for identifying infants with severe infection and adverse prognosis. Advances in flow cytometry have allowed simultaneous measurement of key markers using only minimal blood volume. Judicious selection of a panel of markers with complementary properties could greatly increase the ability of neonatologists to diagnose infection and discern valuable prognostic information.

Quantitative Measurement of Monocyte HLA-DR Expression in the Identification of Early-Onset Neonatal Infection

BACKGROUND

This study aimed to evaluate the diagnostic utilities of monocyte HLA-DR as an infection marker in the identification of early-onset clinical infection and pneumonia in newborn infants.

METHODS

Term newborns in whom infection was suspected when they were <72 h of age were eligible for enrollment in the study. C-reactive protein (CRP), monocyte HLA-DR and neutrophil CD64 expressions were quantitatively measured at the time of sepsis evaluation (0 h) and 24 h afterwards by flow cytometry and standard laboratory method.

RESULTS

A total of 288 infants with suspected sepsis were investigated, and 93 were found to be clinically infected. There were no significant differences in monocyte HLA-DR expression between the infected, non-infected and control groups at 0 h (median (interquartile range): 13,986 (10,994-18,544), 14,234 (12,045-17,474) and 18,441 (14,250-21,537) antibody phycoerythrin (PE) molecules bound/cell), and between infected and non-infected infants at 24 h (median (interquartile range): 17,772 (12,933-25,167) and 19,406 (14,885-24,225) antibody PE molecules bound/cell). The areas under the receiver operating characteristics (ROC) curves for HLA-DR, CD64 and CRP were 0.52-0.54, 0.88-0.94 and 0.75-0.77, respectively. We were unable to determine an optimal cutoff value for HLA-DR, as the diagnostic utilities of any cutoff point on the ROC curves were unable to satisfy the criteria (i.e. sensitivity and specificity >or=80%) for consideration as an useful diagnostic marker of infection.

CONCLUSIONS

Our findings did not support the use of monocyte HLA-DR alone or in combination with other infection markers in the diagnosis of early-onset clinical infection and pneumonia in term newborns.

Comparison of neutrophil CD64 expression, manual myeloid immaturity counts, and automated hematology analyzer flags as indicators of infection or sepsis

There is a clear need for improved indicators of infection or sepsis to increase the sensitivity and specificity of both diagnosis and therapeutic monitoring. One of the effects of inflammatory cytokines on the innate immune response is the rapid up-regulation of CD64 expression on the neutrophil membrane. We and others have hypothesized that the measurement of neutrophil CD64 expression might represent an improved diagnostic indicator of infection and sepsis. In this study we assessed the relative ability of flow cytometric neutrophil CD64 measurements, neutrophil counts, myeloid immaturity differential counts, and flagging on an automated hematology analyzer to correlate with the presence of infection, as determined by a retrospective clinical scoring system of infection or sepsis. A total of 160 blood samples were randomly selected to derive equal proportions of the 3 categories of flags on a Coulter STKS blood counter that indicate the presence of a myeloid left shift. The patients for these samples were scored by retrospective chart review and placed into 4 groups on the basis of likelihood of infection, sepsis, or severe tissue injury. Neutrophil CD64 expression demonstrated a superior sensitivity (94.1%), specificity (84.9%), and positive predictive likelihood ratio (6.24), compared with neutrophil counts (sensitivity, 79.4%; specificity, 46.8%; positive predictive likelihood ratio, 1.49), band counts (sensitivity, 87.5%; specificity, 43.5%; positive predictive likelihood ratio, 1.55), myeloid immaturity fraction (sensitivity, 94.6%; specificity, 84.5%; positive predictive likelihood ratio, 2.12), and flagging on an automated hematology analyzer (sensitivity, 94.1%; specificity, 40.5%; positive predictive likelihood ratio, 1.58). Relative to the other laboratory parameters, the neutrophil CD64 parameter also provided the best separation of the 4 clinical groups. The findings indicate that neutrophil CD64 expression as determined by quantitative flow cytometry is an improved diagnostic indicator of infection/sepsis relative to current laboratory indicators of relative or absolute myeloid cell counts or hematology analyzer flagging algorithms.

Improved diagnostic approaches to infection/sepsis detection

Sepsis is a major healthcare problem from the perspective of mortality and economics. Advances in diagnostic detection of infection and sepsis have been slow, but recent advances in both soluble biomarker detection and quantitative cellular measurements promise the availability of improved diagnostic techniques. Though the promise of cytokine measurements reaching clinical practice have not matured, procalcitonin levels are currently available in many countries and appear to offer enhanced diagnostic distinction between bacterial and viral etiologies. Cellular diagnostics is poised to enter clinical laboratory practice in the form of neutrophil CD64 measurements, which offer superior sensitivity and specificity to conventional laboratory assessment of sepsis. Neutrophil CD64 expression is negligible in the healthy state. However, it increases as part of the systemic response to severe infection or sepsis. The combination of cellular proteomics, as in the case of neutrophil CD64 quantification, and selected soluble biomarkers of the inflammatory response, such as procalcitonin or triggering receptor expressed on myeloid cells (TREM)-1, is predicted to remove the current subjectivity and uncertainty in the diagnosis and therapeutic monitoring of infection and sepsis.

Immunologic markers in the neonatal period: diagnostic value and accuracy in infection

Diagnosis of early-onset neonatal infection has led to the development of several screening tests including C-reactive protein, a very commonly used marker, and cytokines (mainly interleukin-6 and -8), alone or in combination with C-reactive protein, based on the premise that their increases in response to infection may precede that of C-reactive protein. In recent years the search for diagnostic tests has turned to procalcitonin, a propeptide of calcitonin, which appears to be a promising marker of infection in newborn infants. Additionally, specific leukocyte cell surface antigens (mainly CD11b and CD64), detected by flow cytometry, are evaluated as markers of neonatal infection, since their expression on the cell membrane increases in substantial quantities after leukocyte activation by bacteria or their cellular products. This review aims to examine the role of these newly available immunologic indices and to assess their validity as diagnostic markers of infection during the neonatal period.

CD64 (Fcgamma receptor I) cell surface expression on maturing neutrophils from preterm and term newborn infants

BACKGROUND

The expression of CD64 (FcgammaRI) is increased from an almost negligible to a marked level on neutrophils in patients with bacterial infections. CD64 expression on neutrophils might therefore be a potential candidate for the diagnosis of bacterial infections in infants.

AIM

This study was performed to monitor changes of neutrophil expression of CD64 during the postpartum period to further evaluate the usefulness of this analysis. The possible influence on the expression of this receptor by other factors was also investigated, including respiratory distress syndrome (RDS) and preterm rupture of the membranes (PROM).

METHODS

Cell surface expression of CD64 on neutrophils from preterm and term newborn infants and healthy adults was analysed by flow cytometry. The expression of the other Fcgamma receptors, CD32 and CD16, and the complement receptors CD11b/CD18 and CD35 was also analysed for comparison.

RESULTS

Neutrophils from preterm newborn infants showed a moderately increased level of CD64 expression that, during their first month of life, was reduced to the level observed on neutrophils from term newborn infants and adults. In contrast, the level of neutrophil expression of CD32 and CD16 was significantly lower in preterm than term newborn infants and adults. Neutrophils from all groups indicated similar levels of CD11b expression, but the expression on neutrophils from newborn infants increased after birth.

CONCLUSION

Our results showed that neutrophil expression of CD64 is moderately increased in preterm newborn infants at birth. It seems not to be influenced by RDS, PROM or other factors related to preterm birth but by bacterial infection.

Neutrophil CD64 is a sensitive diagnostic marker for early-onset neonatal infection

This prospective study aimed to evaluate the diagnostic utilities of neutrophil CD64 expression for the identification of early-onset clinical infection and pneumonia in term infants and to define the optimal cutoff value so that it may act as a reference with which future studies can be compared. Term newborns in whom infection was suspected when they were <72 h of age were recruited into the study. C-reactive protein (CRP) and expression of CD64 on neutrophils were measured at 0 h (at the time of sepsis evaluation) and 24 h. The sensitivity, specificity, positive predictive value, and negative predictive value (NPV) of CRP, CD64, and the combination of these two markers for predicting neonatal sepsis were determined. A total of 338 infants with suspected clinical sepsis were investigated, 115 of whom were found to be clinically infected. CRP and CD64 in infected infants were both significantly elevated at 0 and 24 h compared with noninfected infants (p < 0.001). The calculated optimal cutoff value for CD64 was 6136 antibody-phycoerythrin molecules bound/cell. CD64 has a very high sensitivity (96%) and NPV (97%) at 24 h. The addition of CRP only marginally enhanced the sensitivity and NPV (97 and 98%, respectively). In conclusion, neutrophil CD64 is a very sensitive diagnostic marker for the identification of early-onset clinical infection and pneumonia in term newborns. The results strongly suggest that measurement of neutrophil CD64 may allow neonatal clinicians to discontinue antibiotic treatment at 24 h in infants who are clinically stable and whose CD64 expressions are below the optimal cutoff level.

Combined use of alcohol hand rub and gloves reduces the incidence of late onset infection in very low birthweight infants

OBJECTIVE

To assess the incidence of late onset (> 72 hours) infection and necrotising enterocolitis (NEC) in very low birthweight (VLBW) infants in two 36 month periods using two hand hygiene protocols: conventional handwashing (HW; first 36 month period); an alcohol hand rub and gloves technique (HR; second 36 month period).

METHOD

VLBW infants admitted to the neonatal intensive care unit during the period December 1993-November 1999 were eligible. A new hand hygiene protocol using alcohol handrub and gloves was introduced in December 1996. Each patient's case record was reviewed retrospectively by two independent investigators using a standard data collection form. The incidence of NEC and systemic infections, including bacterial or fungal septicaemia, meningitis, and peritonitis, in the two periods were compared.

RESULTS

The HW and HR groups contained 161 and 176 VLBW infants respectively. The incidence of late onset systemic infection decreased from 13.5 to 4.8 episodes (including NEC)/1000 patient days after introduction of the HR regimen, representing a 2.8-fold reduction. Similarly, the incidence of Gram positive, Gram negative, and fungal infections decreased 2.5-fold, 2.6-fold, and 7-fold respectively. There was also a significant reduction in the incidence of NEC in the HR group (p < 0.0001). Subgroup analysis revealed that the incidence of methicillin resistant Staphylococcus aureus (MRSA) septicaemia was significantly decreased in the second 36 month period (p = 0.048). The clinical data suggest that infants in the HW group had significantly earlier onset of sepsis (p < 0.05) and required oxygen supplementation for longer (p < 0.05) than those in the HR group. Significantly more VLBW infants were discharged from the neonatal intensive care unit without ever being infected (p < 0.0001), and also significantly fewer infants had more than one episode of infection in the HR group (p < 0.0001).

CONCLUSION

The introduction of the HR protocol was associated with a 2.8-fold reduction in the incidence of late onset systemic infection, and also a significant decrease in the incidence of MRSA septicaemia and NEC in VLBW infants. This decrease in infection rate was maintained throughout the second 36 month period.

A standardized procedure for quantitation of CD11b on polymorphonuclear neutrophil by flow cytometry: potential application in infectious diseases

An up-regulation of the surface marker CD11b has been demonstrated during polymorphonuclear (PMN) cell activation. CD11b over-expression is often associated with inflammation and is considered as an early marker of infection. However, the absence of standardized assay and the variability of preanalytical settings leading to PMN artifactual activation have compromised the interest of this marker. In the present study a standardized quantitative flow cytometry assay directly performed in whole blood has been used to determine CD11b expression on PMN cells. The results indicate that quantitative flow cytometry can provide consistent CD11b density values between laboratories provided that a calibration system is used including specific calibrators, reagents and protocols. This method allowed us to evidence an up-regulation of CD11b expression for infected patients. This quantitation is a standardized and potentially useful method in clinical situations implying quantitative CD11b expression variations.

Diagnostic markers of infection in neonates

Diagnostic markers of infection are useful indicators of neonatal sepsis. Serial measurements of infection markers can improve diagnostic sensitivity, and the use of multiple markers can enhance diagnostic accuracy. Current evidence suggests that promising markers may be useful for early termination of antimicrobial treatment, but none of the current diagnostic tests are sensitive and specific enough to influence the clinical decision for withholding antibiotic treatment at the onset of suspected infection.

Expression and regulation of B7 family molecules on macrophages (MPhi) in preterm and term neonatal cord blood and peripheral blood of adults

BACKGROUND

Macrophage (MPhi) receptors of the B7 family (CD80, CD86) play a crucial role in T cell activation: the lack of costimulation leads to anergy or apoptosis of reactive T cells. MPhi may differentiate into different subsets, the balance of which defines MPhi-dependent T cell reactions. The aim of this study was to examine neonatal and adult T cell response with respect to the costimulatory MPhi-potential in order to identify molecular predictors for the neonatal immune defense.

METHODS

MPhi from peripheral blood (PBMPhi) or cord blood (CBMPhi) were stimulated with interferon-gamma (IFN-gamma), cyclic adenosine monophosphate (cAMP), CD40 ligand (CD40L), or alphaCD3.

RESULTS

As compared to PBMPhi, CBMPhi showed a significantly decreased upregulation of CD80 and/or CD86 after stimulation with IFN-gamma, cAMP, CD40L, and alphaCD3. Accordingly, the proliferative T cell response was impaired in the presence of CBMPhi. The fraction of T cells that underwent cell death was higher, and blast formation was significantly lower than that observed in the presence of PBMPhi.

CONCLUSIONS

CBMPhi, as compared to PBMPhi, delivered fewer costimulatory but more cytotoxic signals to T cells. These observations suggest that MPhi are one factor explaining the suboptimal immune defense of neonates and their increased susceptibility to infection. Using the costimulatory MPhi-potential as a predictor for immune responses requires a separate reference value system in neonatology.