Can Fetal Umbilical Venous Blood Be a Reliable Source for Admission Complete Blood Count and Culture in NICU Patients?

Umbilical Cord Blood as an Alternative to Neonatal Blood for Complete Blood Count: A Comparison Study

OBJECTIVE

To assess concordance between umbilical cord blood (UCB) and neonatal blood (NB) laboratory test results at birth.

STUDY DESIGN

This retrospective study considered very preterm neonates (<32 weeks' gestational age) admitted to a tertiary neonatal intensive care unit from 2012 to 2023. Inclusion criteria required neonates with a complete blood count measured in both UCB and NB drawn within 2 hours after birth. Median hemoglobin (Hb) and hematocrit (Hct) concentrations were compared between UCB (venous samples) and NB (venous, arterial, or capillary samples).

RESULTS

A total of 432 neonates with paired UCB and NB values were included in the study. Hb concentration in UCB was 14.7 g/dL (IQR 13.5-16.1 g/dL) compared with 14.8 g/dL (IQR 12.6-19.3 g/dL) in venous NB samples, 13.9 g/dL (IQR 12.9-15.3 g/dL) in arterial NB and 18.7 g/dL (IQR 16.6-20.8 g/dL) in capillary NB. The regression equation showed a correction factor of 1.08 for converting Hb values from UCB to venous NB. Median Hct concentration in UCB was 0.45 L/L (IQR: 0.41-0.49 L/L) compared with 0.48 L/L (IQR 0.43-0.54 L/L) in venous NB, 0.42 L/L (IQR 0.38-0.45 L/L) in arterial NB and 0.57 L/L, (IQR 0.51-0.63 L/L) in capillary NB.

CONCLUSIONS

Hb and Hct concentrations measured in UCB are similar to those measured in venous blood in very preterm infants and are valid alternatives for NB tests at birth. Hb and Hct concentrations in arterial and capillary NB are respectively lower and higher compared with UCB measurements.

Umbilical cord blood culture for early onset sepsis in preterm infants

BACKGROUND

Umbilical cord blood culture (UCBC) may have a diagnostic utility for early onset sepsis (EOS) detection in preterm infants. It may prevent sampling the newborn and collect a higher volume of blood for pathogenic identification.

METHODS

Retrospective analysis at a tertiary care center in Canada of preterm infants ≤ 34 0/7 weeks' gestation with UCBC taken at birth.

RESULTS

Of 505 admitted infants, 195 had UCBC. 170 UCBCs were negative; 44 of these had also negative neonatal blood culture (NBC). No infants with negative UCBC showed EOS symptoms in the first week of life. 25 UCBCs were positive: 18 were contaminants (all with negative NBC) and 7 were confirmed as EOS. 18 infants with UCBC contaminants remained asymptomatic. 7 EOS cases were identified, with varying bacteriological profiles; 5 displayed sepsis symptoms while 2 were asymptomatic. Risk of EOS increased with prolonged rupture of membranes.

CONCLUSIONS

UCBC effectively detected EOS establishing it as a method with possibly better diagnostic performance than NBC in high-risk neonates. Further studies are needed to improve UCBC technique and lower contamination rates.

IMPACT

Umbilical cord blood culture has a higher bacterial identification rate than peripheral venous blood culture for the early identification of early-onset sepsis in preterm infants. Umbilical cord blood cultures that showed no growth were reliable predictors of not developing early onset sepsis. Umbilical cord blood culture should be considered as part of the evaluation for early onset sepsis in the preterm infants.

Cord blood sampling for neonatal admission laboratory testing-An evidence-based blood conservation strategy

Historically, blood for admission laboratory studies in neonates was obtained through direct neonatal phlebotomy. Over the past decade there has been an increase in studies evaluating the validity and clinical impact of using a cord blood sample for many admission laboratory studies. This article reviews various studies that together have shown that using cord blood samples for admission testing in neonates is both acceptable and beneficial.

Point-of-Care Verification of Blood Culture Volume in Neonates: A Feasibility Trial

BACKGROUND

Blood cultures remain the gold standard for the diagnosis of sepsis. However, volumes of blood submitted for cultures often do not match the recommended values. We propose a simple intervention aimed to verify the volume of blood sampled using a scale. This study was undertaken in preparation for a future, multicenter, pre- and post-intervention trial. Our primary objective was to test the feasibility (uptake and retention) of this future intervention.

MATERIALS AND METHODS

This study was conducted at a neonatal department in Warsaw, Poland, over a period of eight months (May to December 2020). Before starting the study, we undertook an educational intervention focused on obtaining adequate blood volumes for culture. The culture bottles that were weighed in advance were distributed in all blood collection areas. Blood volume was verified by weighing the bottle immediately after blood inoculation. The calculated value was communicated to the collecting clinician and recorded. The primary outcome measure was the percentage of blood culture submissions for which the blood volume inoculated into the bottles was determined by weighing.

RESULTS

During the study period, 244 blood samples were collected for culture, out of which 205 samples were weighed (84.0%, CI95 [78.8% to 88.4%]). This high proportion remained stable throughout the study period. We have not observed any adverse events related to the study.

CONCLUSIONS

The point-of-care verification of blood culture volume using a scale was feasible to implement. Since we have met our pre-established criterion for success, a future, definitive trial is likely to proceed.

Red blood cell parameters in early childhood: a prospective cohort study

OBJECTIVES

Red blood cell parameters are frequently used biomarkers when assessing clinical status in newborns and in early childhood. Cell counts, amounts, and concentrations of these parameters change through gestation and after birth. Robust age-specific reference intervals are needed to optimize clinical decision making.

METHODS

The Copenhagen Baby Heart Study (CBHS) and the COMPARE study are prospective cohort studies including red blood cell parameters from 7,938 umbilical cord blood samples and 295 parallel venous blood samples from newborns with follow-up at two and at 14-16 months after birth.

RESULTS

For venous blood at birth, reference intervals for hemoglobin, erythrocytes, and hematocrit were 145-224 g/L, 4.1-6.4 × 10¹²/L, and 0.44-0.64, respectively. Hemoglobin, erythrocytes, and hematocrit were lower at birth in children delivered by prelabor cesarean section compared to vaginal delivery. Conversion algorithms based on term newborns were: venous hemoglobin=(umbilical cord hemoglobin-86.4)/0.39; venous erythrocytes=(umbilical cord erythrocytes-2.20)/0.44; and venous hematocrit=(umbilical cord hematocrit-0.24)/0.45.

CONCLUSIONS

This study presents new reference intervals for red blood cell parameters in early childhood, describes the impact of delivery mode, and provide exact functions for converting umbilical cord to venous blood measurements for term newborns. These findings may improve clinical decision making within neonatology and infancy and enhance our clinical understanding of red blood cell parameters for health and diseases in early life.

Cord Platelet Count of Full-Term Neonates in Relation to ABO Incompatibility and Glucose-6-Phosphate Dehydrogenase Levels: A Retrospective Cohort Study

Background The immunoglobulin G of mothers with O blood type may sensitize the platelets of their neonates with A (O-A incompatibility) or B (O-B incompatibility) blood type. As the expression and antigenicity of the B antigen on platelets is less than that of the A antigens, we have hypothesized that platelet count is higher in the O-B incompatibility group compared to the O-A incompatibility group. There is controversy about whether glucose-6-phosphate dehydrogenase (G6PD) deficiency, without evidence of hemolysis, is associated with a lower platelet count than G6PD-normal. Aim To assess whether platelet count is higher in the O-B than in the O-A incompatible neonates and whether it correlates with their G6PD levels. Methods This study was a retrospective cohort study on a sample of 835 healthy neonates born at ≥38 weeks gestation who were either A or B blood types with mothers that carried the blood type O Rh-positive. The platelet count (thousand per microliter) from umbilical cord venous blood (UCVB) was used. A G6PD level of 11.0 units/gram of hemoglobin (U/g Hb) was considered the lower reference limit. G6PD deficiency was defined as a G6PD level of <3.3 U/g Hb in both sexes. Intermediate G6PD deficiency in females was described as a G6PD level of 3.3-8.8 U/g Hb. Results The mean UCVB platelet count was higher in female neonates compared to male neonates (n=389, 283±65 versus n=446, 272±73, p=0.01). The mean UCVB platelet count was higher in the O-B incompatibility group in both male (n=114, 291±82 versus n=103, 266±63) and female neonates (n=83, 303±66 versus n=81, 278±58) with G6PD levels of >8.8 U/g Hb. There was a positive weak correlation between UCVB platelet counts and G6PD levels only in O-B incompatible female neonates (n=176, r=0.23, p=0.002). The partitioning and combined 95% reference intervals (RIs) of the UCVB platelet count were presented. Conclusion The platelet count was higher in the O-B incompatibility group compared to the O-A incompatibility group, but only when the G6PD level was >8.8 U/g Hb. A correlation between UCVB platelet count and G6PD levels was found only among O-B incompatible female neonates. These findings may have an important implication in estimating RIs of the UCVB platelet count, however, they need to be confirmed and explored in future research.

The Novel Use of Umbilical Cord Blood to Obtain Complete Blood Counts for Critical Neonatal Assessment

Background: Neonates undergoing clinical evaluations are often subjected to potentially painful phlebotomy for laboratory tests. The use of cord blood laboratory values for admission has been suggested as a means to decrease the risk of painful venipuncture and anemia.

Methods: Peripheral and umbilical cord blood complete blood count (CBC) results were obtained from infants who required a CBC. Results were compared using the Sysmex XN heme analyzer (Sysmex, Kobe, Japan).

Results: White blood cell (WBC) and hemoglobin (HgB) values were significantly higher in peripheral samples than in cord samples. The mean cord WBC count was 14.1 × 10³/mm³ versus 15.6 × 10³/mm³ peripherally (p < 0.001). The mean cord HgB was 15.8 g/dL versus 16.8 g/dL peripherally (p < 0.001). Cord platelet (Plt) counts were, conversely, lower in peripheral samples than in cord samples (264.8 × 10³/mm³ versus 242.3 × 10³/mm³, respectively; p < 0.001). Although statistically different, the mean CBC values from both samples were within the reference ranges. Delayed cord clamping (DCC) increased peripheral versus cord HgB difference nearly threefold (0.6-1.7 g/dL; p = 0.01).

Conclusions: Cord blood is an acceptable source for CBC blood sampling in newborn infants and can be used for clinical decisions. CBC laboratory values for cord blood remained within the peripheral blood reference range, with slight variability between the two samples.

Umbilical cord blood culture in neonatal early-onset sepsis: a systematic review and meta-analysis

BACKGROUND

Peripheral blood culture (PBC) is considered the gold standard for diagnosis of neonatal early-onset sepsis (EOS), but its diagnostic value can be questioned. We aimed to systematically asses the diagnostic test accuracy (DTA) of umbilical cord blood culture (UCBC) for EOS.

METHODS

A systematic literature search was performed in PubMed, Embase, Web of Science, and the Cochrane Library. Studies performing UCBC for the diagnosis of EOS were included.

RESULTS

A total of 1908 articles were screened of which 17 were included. Incidences of positive PBC and UCBC were low in all studies. There was a large heterogeneity in the consistency between positive PBC and UCBC outcomes. PBC had a pooled sensitivity of 20.4% (95% CI 0.0-40.9) and specificity of 100.0% (95% CI 100.0-100.0) compared to 42.6% (95% CI 12.7-72.4%) and 97.8% (95% CI 93.1-100.0) of UCBC for clinical EOS, defined as clinical sepsis regardless of PBC outcomes.

CONCLUSIONS

This systematic review shows that, compared to PBC, UCBC has higher sensitivity and comparable specificity for clinical EOS and might be considered as diagnostic test for EOS. Due to the limited number of studies, low incidences of EOS cases, and the imperfect reference standards for EOS, results should be interpreted cautiously.

IMPACT

This is the first systematic review and meta-analysis investigating the diagnostic test accuracy of umbilical cord blood culture for neonatal early-onset sepsis. Peripheral blood culture is considered the gold standard for diagnosis of neonatal early-onset sepsis, but its value for this specific diagnosis can be questioned. Umbilical cord blood culture has higher sensitivity and comparable specificity for diagnosis of neonatal early-onset sepsis compared to peripheral blood culture, circumventing the risk for iatrogenic anemia and consequently might be used as a diagnostic tool for early-onset sepsis. Quality of evidence was regarded as low due to imperfect diagnostic methods of neonatal early-onset sepsis.

Utilizing umbilical cord blood - Minimizing blood sampling and pain in healthy infants at risk for polycythemia

BACKGROUND

Exposure to pain in early life was associated with long term consequences, therefore strategies for minimizing painful procedures in newborns should be employed. The utility and reliability of cord blood CBC was demonstrated before, however data regarding use of cord blood in healthy infants at risk for polycythemia are lacking.

METHODS

A single-center, paired-sampling prospective laboratory study including all healthy asymptomatic infants born after 36 weeks gestation who were SGA (<2500 g), LGA (>4000 g), or born to mothers with diabetes in pregnancy. Blood count indices were compared between umbilical and neonatal capillary or venous blood samples. In order to predict cut-off values for neonatal polycythemia using umbilical hematocrit, receiver operator curves (ROC) were plotted.

RESULTS

Paired samples were collected from 433 infants. Mean gestational age and birth-weight were 39.0 ± 1.3 weeks and 3489 ± 682 g. Hemoglobin, hematocrit and WBC values were lower in cord blood compared to neonatal, but PLT count was higher. Pearson r showed only modest correlation between peripheral capillary and umbilical or venous Hct - 0.35 (p < 0.001), and 0.44 (p < 0.001), respectively. In order to try and capture clinically significant polycythemia ROC was plotted for hematocrit >70% and <40%. In our cohort, using the calculated cutoff values (>51% and <35%) could have resulted in a decrease of 72% of neonatal blood draws.

CONCLUSION

This analysis should be interpreted with caution, as currently it cannot support the routine use of umbilical samples' hematocrits for making treatment decision in newborns at risk for polycythemia. Further larger studies are needed.

Immunohematology testing using umbilical cord blood: review of the literature, survey of practice and guidance development

BACKGROUND

Following delivery, blood tests are performed on umbilical cord blood (CB) to avoid neonatal venipuncture. Despite widespread and longstanding CB testing, no guidelines exist to suggest which immunohematology tests should be performed on CB.

STUDY DESIGN AND METHODS

We performed a scoping review, surveyed national practice, and developed guidance statements concerning CB testing. Database searches identified relevant articles. A survey was sent to all Canadian hospitals and transfusion laboratories that perform perinatal testing. A national panel of experts was convened to develop guidance statements.

RESULTS

A total of 116 articles met the inclusion criteria and were summarized. Literature on CB testing is limited; few studies have investigated laboratory testing methodologies or validated CB test results with peripheral samples. The survey was completed by 580/597 institutions (97%); 85% were community hospitals and 16% had a neonatal intensive care unit. There is diversity in the types of CB tests performed and variability in practice. While most centers order appropriately, some laboratories routinely perform CB tests that are not clinically indicated (e.g., direct antiglobulin testing for all neonates) and other do not perform CB tests when results would be beneficial (e.g., phenotype on CB when mother has a clinically significant antibody). Fifteen guidance statements were developed.

DISCUSSION

This study highlights variability in CB testing, likely reflecting evidence gaps, methodology differences between studies, and lack of guidelines. CB tests should only be performed when indicated and validated on this sample type. The presented guidance statements aim to standardize practice and encourage judicious CB sampling.

Comprehensive Morphological Assessment of Cord Blood: Normal Values and the Prevalence of Morphologically Aberrant Leukocytes

INTRODUCTION

Cord blood (CB) is becoming a valuable source for stem cells utilized in a variety of cell therapy applications, as well as for newborn diagnostics. Some parameters of the CB cellular components can be provided by automated analyzers, while others, such as immature or aberrant cells, require blood film morphological assessment. The objectives of the study were to establish normal CB morphology and to determine the prevalence of morphologically aberrant leukocytes in CB.

METHODS

We performed a comprehensive morphological analysis of 100 CB samples taken from healthy term and appropriate-for-gestational-age neonates born to healthy mothers, preterm neonates, neonates of diabetic mothers, and small-for-gestational-age neonates. Blood counts were assessed, and manual morphological analyses were performed by laboratory specialists.

RESULTS

The manual differential count of normal CB samples established the following values: 47.8 ± 10.7% neutrophils, 31.2 ± 9.8% lymphocytes, 10.0 ± 4.0% monocytes, and 3.0 ± 2.5% eosinophils, with no significant sex-related differences. Blasts were observed in 44/100 samples with an average of 0.5 ± 0.7% per sample, and only a minor left shift was observed. There were significant populations of large granular lymphocytes (19.1 ± 10.6% of the total lymphocytes) and morphologically aberrant lymphocytes (12.4 ± 5.4% of the total lymphocytes) in the samples, irrespective of neonatal status. The differentials of preterm CB samples differ significantly from normal term CB samples, including the reverse of neutrophils/lymphocytes ratio, and the lack of basophils.

CONCLUSIONS

Normal values and unique morphological features in the CB of neonates are described. The abundant morphologically aberrant lymphocytes in CB may represent an immature state of the immune system at birth.

Umbilical Cord Blood Use for Admission Blood Tests of VLBW Preterm Neonates: A Randomized Control Trial

OBJECTIVE

 Umbilical cord blood (UCB) for admission laboratories is an approach to decrease anemia risk in very low birth weight (VLBW) neonates. We hypothesized that UCB use results in higher hemoglobin concentration [HgB] around 24 hours of life.

STUDY DESIGN

 A randomized control trial among VLBW infants whose admission laboratories were drawn from UCB (n = 39) or the infant (n = 41) in three U.S. military NICUs (clinicaltrials.gov#NCT02103296).

RESULTS

 No demographic differences were observed between groups. UCB infants had higher [HgB] at 12 to 24 hours of life (15.5 vs. 14.0 g/dL, p = 0.02). The median time to first transfusion was 17 days longer in the experimental group (p = 0.04), and at discharge, their number of donor exposures was lower (1.1 vs. 1.8, p = 0.04).

CONCLUSION

 In the first 24 hours of life that is a period of higher risk for hemodynamic instability, UCB utilization for admission bloodwork in VLBW infants results in higher [HgB].

KEY POINTS

· Umbilical cord blood laboratory work in preterm infants is feasible.. · Cord blood use for admission laboratories results in increased hemoglobin in the first 24 hours of life.. · Cord blood use for admission laboratories delays time to first transfusion in preterm infants..

Feasibility and accuracy of cord blood sampling for admission laboratory investigations: A pilot trial

AIM

Phlebotomy losses greatly contribute to anaemia following preterm birth. Therefore, the possibility of drawing initial tests from the placenta seems attractive. There is a lack of literature regarding the feasibility and accuracy of pathology tests taken from umbilical arterial and venous (UAB/UVB) compared to blood collected from the newborn.

METHODS

UAB and UVB complete blood pictures were compared with the initial neonatal blood test. The relationship between UAB, UVB and neonatal complete blood picture values was determined by Spearman's Rho correlation with absolute values compared by Kruskal-Wallis. P < 0.05 was considered significant.

RESULTS

Neonatal haemoglobin, white cell count, immature/total ratio and platelets were significantly correlated to the corresponding values in the UAB and UVB (all P < 0.001). While UAB and UVB haemoglobin and white cell count were similar, both were significantly lower than the neonatal values (P < 0.001 and P = 0.014, respectively). No difference was seen for immature/total ratio and platelet concentrations. UVB blood culture (BC) was feasible (90%), even with delayed cord clamping, and the UVB BC volume was significantly higher (P < 0.001), with a low rate of BC contamination (1.5%).

CONCLUSIONS

Our findings support the feasibility and accuracy of umbilical blood in place of blood collected from the newborn. This reduces the phlebotomy losses and allows higher blood volume collection which may increase the sensitivity of BC collection.

Reference intervals for complete blood count from Umbilical Cord Blood in newborns and comparison with Venous Blood Values

Background and Objective:

Umbilical cord blood which can be obtained by a non-invasive method can be informative about the clinical status of the newborn. It was aimed to establish reference intervals for umbilical cord blood parameters, and to compare complete blood count results between umbilical cord and venous blood samples in this study.

Methods:

This study was conducted at Medipol University Sefaköy Hospital, Department of Pediatrics, Istanbul, Turkey. A total of 1898 newborns who were born in a two-year period between January 2018 and December 2019 were included in the study. Venous blood samples were taken from 184 of them, and umbilical cord blood samples were taken from 1714 newborns.

Results:

The percentiles were determined according to gender and delivery method for the hematological parameters of umbilical cord blood. While mean platelet, eosinophil and mean corpuscular volume values were similar between the groups (p>0.05 for each), and significant differences were found between the groups in terms of all other mean hematological parameters (p<0.05 for each).

Conclusion:

The results of the complete blood count of umbilical cord blood samples can provide reliable information about the newborn. There are significant differences between umbilical cord and venous blood samples in terms of hematological parameters. For these reasons, it is necessary to determine reliable value ranges for umbilical cord blood hematological parameters in newborns. Data of our study can be a guide for further studies and clinicians.

Suitability of Placental Blood Samples of Newborns for Pre-Transfusion Testing

Objective: To show concordance between heel stick and placental blood sample pairs for newborns' pre-transfusion testing and to validate placental blood's tube and gel methodology. Methods: Placental samples were collected for pre-transfusion testing at birth from 78 singleton and twin newborns admitted to our Mother-Baby Unit to compare with the results of heel stick samples taken from same newborns. Gestational age ≥35 weeks, weight ≥2,000 g. The study was approved by the Institutional Review Board (IRB). Informed consent was obtained from newborn parents. ABO blood group, Rhesus factor (Rh), direct antiglobulin test (DAT), and antibody screen were performed. Ortho ProVue Analyzer was used for tube and gel methods. McNemar's test for paired categorical data was performed. Results: One hundred percent concordance in 78 pairs for ABO and Rh. Seventy-four pairs were tested for antibodies, 72 were both negative, 1 was both positive, and 1 gave discordant result. Ninety-nine percent concordance, p = 0.999. Sixty-five pairs were both DAT negative, seven were both DAT positive, and six gave discordant results. Ninety-two percent concordance, p = 0.68. Placental blood gave identical results comparing tube with gel methods. Conclusions: Placental blood is suitable for pre-transfusion testing and can replace heel sticks. Placental blood tube and gel methods are validated.

Correlation of haematological parameters and C-reactive protein between cord blood and first post-natal blood sample in preterm neonates: A prospective observational study

AIM

There is some recent evidence on the utility of the cord blood as a reliable source for admission complete blood count in preterm neonates. However, there is a need to validate other laboratory parameters from the cord blood such as C-reactive protein (CRP) to rule out neonatal sepsis. The present study was carried out to evaluate the correlation between haematological parameters and CRP obtained from the cord blood to the first post-natal blood sample, for it to be considered as a reliable alternative.

METHODS

A total of 89 paired cord blood and first post-natal blood samples were prospectively analysed to assess the haematological parameters (complete blood count) and CRP. Pearson's coefficient was calculated to assess the correlation between the cord blood and the first post-natal blood sample.

RESULTS

When Pearson's correlation coefficient was calculated for various haematological parameters, it showed good correlation coefficient of 0.84 for total leukocyte count, 0.84 for absolute neutrophil count count, 0.87 for immature to total neutrophil ratio and 0.95 for CRP. The correlation coefficient was 0.64 for haemoglobin and 0.36 for platelet count.

CONCLUSION

There is a strong correlation between the majority of haematological parameters and CRP obtained from the cord blood with the first post-natal blood sample in preterm neonates, except the platelet count. Hence, umbilical cord blood is a feasible and reliable alternative source for assessment of haematological parameters and CRP for the first post-natal blood sample, thereby avoiding a painful prick in these fragile preterm neonates.

Clinical and Immunological Metrics During Pediatric Rhesus Macaque Development

Background: Clinical measurements commonly used to evaluate overall health of laboratory animals including complete blood count, serum chemistry, weight, and immunophenotyping, differ with respect to age, development, and environment. This report provides comprehensive clinical and immunological reference ranges for pediatric rhesus macaques over the first year of life. Methods: We collected and analyzed blood samples from 151 healthy rhesus macaques, aged 0-55 weeks, and compared mother-reared infants to two categories of nursery-reared infants; those on an active research protocol and those under derivation for the expanded specific-pathogen-free breeding colony. Hematology was performed on EDTA-anticoagulated blood using a Sysmex XT2000i, and serum clinical chemistry was performed using the Beckman AU480 chemistry analyzer. Immunophenotyping of whole blood was performed with immunofluorescence staining and subsequent flow cytometric analysis on a BD LSRFortessa. Plasma cytokine analysis was performed using a Millipore multiplex Luminex assay. Results: For hematological and chemistry measurements, pediatric reference ranges deviate largely from adults. Comparison of mother-reared and nursery-reared animals revealed that large differences depend on rearing conditions and diet. Significant differences found between two nursery-reared cohorts (research and colony animals) indicate large influences of experimental factors and anesthetic events on these parameters. Immune cells and cytokine responses presented with distinct patterns for infants depending on age, birth location, and rearing conditions. Conclusions: Our results illustrate how the immune system changed over time and that there was variability among pediatric age groups. Reference ranges of results reported here will support interpretations for how infection and treatment may skew common immune correlates used for assessment of pathology or protection in research studies as well as help veterinarians in the clinical care of infant non-human primates. We highlighted the importance of using age-specific reference comparisons for pediatric studies and reiterated the utility of rhesus macaques as a model for human studies. Given the rapid transformation that occurs in multiple tissue compartments after birth and cumulative exposures to antigens as individuals grow, a better understanding of immunological development and how this relates to timing of infection or vaccination will support optimal experimental designs for developing vaccines and treatment interventions.