The gut microbiota is associated with immune cell dynamics in humans.

The gut microbiota influences development1-3 and homeostasis4-7 of the mammalian immune system, and is associated with human inflammatory8 and immune diseases9,10 as well as responses to immunotherapy11-14. Nevertheless, our understanding of how gut bacteria modulate the immune system remains limited, particularly in humans, where the difficulty of direct experimentation makes inference challenging. Here we study hundreds of hospitalized-and closely monitored-patients with cancer receiving haematopoietic cell transplantation as they recover from chemotherapy and stem-cell engraftment. This aggressive treatment causes large shifts in both circulatory immune cell and microbiota populations, enabling the relationships between the two to be studied simultaneously. Analysis of observed daily changes in circulating neutrophil, lymphocyte and monocyte counts and more than 10,000 longitudinal microbiota samples revealed consistent associations between gut bacteria and immune cell dynamics. High-resolution clinical metadata and Bayesian inference allowed us to compare the effects of bacterial genera in relation to those of immunomodulatory medications, revealing a considerable influence of the gut microbiota-together and over time-on systemic immune cell dynamics. Our analysis establishes and quantifies the link between the gut microbiota and the human immune system, with implications for microbiota-driven modulation of immunity.

Mast cell proliferation in the cerebrospinal fluid after intraventricular administration of anti-B7H3 immunotherapy.

Omburtamab is a B7H3-specific murine monoclonal antibody. B7H3 (CD 276) is a member of the B7 family of immune checkpoint co-inhibitory receptors overexpressed on many human malignancies. Radioimmunotherapy with 124I- or 131I-omburtamab administered in the cerebrospinal fluid (CSF), intraperitoneal or intratumoral cavity is currently under investigation for the treatment of CNS malignancies. The immunologic effects of anti-B7H3 therapy are not fully elucidated. A 6-year-old male was diagnosed with metastates of neuroblastoma to the received intraventricular 131I-omburtamab on an IRB-approved protocol. A treatment cycle consisted of a 2 mCi dosimetry dose and a 50 mCi treatment dose. Dosimetry by serial imaging, pharmacokinetics and safety were investigated. Clinical status, magnetic resonance imaging, CSF cell count and cytology were evaluated pre- and post-131I-omburtamab at 5 and 26 weeks. The patient did well with cycle 1. Three hours after the dosimetry dose of cycle 2, he developed a fever (39 °C), chills and headache. Blood and CSF samples were sent for culture. CSF was notable for nucleated cell pleocytosis with profound mast cell proliferation consistent with chemical meningitis. He was treated with supportive care; symptoms resolved over 48 h. Further therapy with 131I-omburtamab was electively discontinued. CSF cell count 5 weeks later demonstrated resolution of CSF pleocytosis. Local-regional administration of intraventricular 131I-omburtamab targeting B7H3 can result in a profound nucleated CSF pleocytosis with mastocytosis consistent with an acute allergic reaction.

Evaluation of peripheral blood mononuclear cell collection by leukapheresis.

BACKGROUND: Adoptive immunotherapy using engineered lymphocytes has shown promising results in treating cancers even in patients who have failed other treatments. As the first essential step, the number of peripheral mononuclear cell (MNC) collection procedures is rapidly increasing. In this retrospective study, we reviewed the collection results to determine factors that affect MNC collection. STUDY DESIGN AND METHODS: We reviewed 184 collections that were performed on 169 adult allogenic donors and patients with acute lymphoid leukemia, chronic lymphoid leukemia, lymphoma, multiple myeloma, or solid-organ tumors. All the leukapheresis procedures were performed after a complete cell count with differential was obtained. Total blood volume (TBV) was defined as processed blood volume divided by patient blood volume. RESULTS: There was a significant association between the precollection MNC count (pre-MNC) and the MNC yields normalized by TBV (r = 0.926; p < 0.001) and a regression formula was created to predict MNC yields. Multiple regression analyses showed that pre-MNC, TBV, and precollection hemoglobin were strongly associated with MNC yield (R 2 = 0.866; F (3180) = 388.472; p < 0.001), and pre-MNC had the greatest influence on MNC yield (ß = 0.960; p < 0.001) followed by TBV (ß = 0.302; p < 0.001), and Hgb (ß = 0.136; p < 0.001). CONCLUSION: Our results suggest that the optimal time for MNC collection can be determined based on pre-MNC and that processing volume should be determined based on collection goal and pre-MNC to optimize and personalize the harvesting procedure.

Reducing Unnecessary and Duplicate Ordering for Ovum and Parasite Examinations and Clostridium difficile PCR in Immunocompromised Patients by Using an Alert at the Time of Request in the Order Management System.

We implemented hospital information system (HIS) alerts to deter unnecessary test orders for ovum and parasite (O&P) exams and Clostridium difficile PCR. The HIS alerts decreased noncompliant O&P orders (orders after >72 h of hospitalization) from 49.8% to 30.9%, an overall decrease of 19%, and reduced noncompliant C. difficile PCR orders (orders <7 days after a previous positive result) from 30.6% to 19.2%, an overall decrease of 31.9%.

Evaluation of new automated hematopoietic progenitor cell analysis in the clinical management of peripheral blood stem cell collections.

BACKGROUND: Successful peripheral blood stem cell transplantation (PBSCT) depends on the collection and infusion of adequate numbers of peripheral blood progenitor cells (PBPCs). Several predictors of PBPC yield are used currently, including white blood cell (WBC) count and CD34 analysis. This study evaluated the utility of the new automated hematopoietic progenitor cell count available on Sysmex XN hematology analyzers (XN-HPCs) in PBSCT. STUDY DESIGN AND METHODS: The performance characteristics of XN-HPC, CD34+, and WBC analysis were compared using 107 matched peripheral blood and apheresis samples. RESULTS: Good correlation was observed between XN-HPC and CD34+ cell counts in peripheral blood (r = 0.88; slope, 0.81) and apheresis collections (r = 0.91; slope, 0.89). Moreover, peripheral blood XN-HPC and CD34 analysis showed comparable ability to predict successful PBPC harvests (≥2 × 10(6) CD34+ cells/kg). At a cutoff of 20 × 10(6) progenitor cells/L, peripheral blood XN- HPC and CD34 analysis both showed negative predictive values (NPVs) of 100% and positive predictive values (PPVs) of 55.4 and 63%, respectively. Using an optimized cutoff of 38 × 10(6) progenitor cells/L, derived from receiver operating characteristic analysis, the PPV for XN-HPC and CD34 analysis increased to 71.4 and 78.9%, respectively, with relatively unchanged NPVs (XN-HPC 97.7%, CD34+ 98.0%). In contrast, the correlation between peripheral blood WBC and CD34 analysis was poor (r = 0.48; slope, 669.85), and the peripheral blood WBC count (cutoff, 10 × 10(9) /L) was a poor predictor of PBPC harvest (NPV 60%, PPV 43.1%). CONCLUSION: XN-HPC compares favorably with CD34 analysis and may be a surrogate for CD34 analysis to predict optimal timing of PBPC collections.

False-positive elevations of carcinoembryonic antigen in patients with a history of resected colorectal cancer.

Routine monitoring of carcinoembryonic antigen (CEA) levels is standard in patients with resected colorectal cancer (CRC). The incidence of false-positives and the upper limits of false-positive elevations have not been previously well characterized. A search of medical records at Memorial Sloan-Kettering Cancer Center identified 728 patients who underwent an R0 resection of locoregional CRC between January 2003 and December 2012 and who had an increase in CEA level above the normal range after a normal perioperative CEA level. Of these, 358 had a false-positive elevation of CEA level, 335 had a true-positive elevation indicative of recurrent CRC, and 35 had a true-positive elevation indicative of the development of a new, non-CRC malignancy. Of those with false elevations, 111 had a single isolated CEA level elevation (median highest CEA level of 5.5 ng/mL) with no further abnormal measurements, whereas 247 had elevations on 2 or more readings, with a median highest level of 6.7 ng/mL. Of these 247 patients with confirmed false-positive CEA level elevations, only 5 (2%) had measurements greater than 15 ng/mL, and no confirmed elevation greater than 35 ng/mL was a false-positive. False-positive CEA test results in the range of 5 to 15 ng/mL are common. Confirmation of CEA elevation in this range before initiating imaging studies may be appropriate. False-positive results greater than 15 ng/mL are rare, and all confirmed CEA levels greater than 35 ng/mL were associated with cancer recurrence.

Comparing Clinician Estimates versus a Statistical Tool for Predicting Risk of Death within 45 Days of Admission for Cancer Patients.

OBJECTIVES: While clinical practice guidelines recommend that oncologists discuss goals of care with patients who have advanced cancer, it is estimated that less than 20% of individuals admitted to the hospital with high-risk cancers have end-of-life discussions with their providers. While there has been interest in developing models for mortality prediction to trigger such discussions, few studies have compared how such models compare with clinical judgment to determine a patient's mortality risk. METHODS: This study is a prospective analysis of 1,069 solid tumor medical oncology hospital admissions (n = 911 unique patients) from February 7 to June 7, 2022, at Memorial Sloan Kettering Cancer Center. Electronic surveys were sent to hospitalists, advanced practice providers, and medical oncologists the first afternoon following a hospital admission and they were asked to estimate the probability that the patient would die within 45 days. Provider estimates of mortality were compared with those from a predictive model developed using a supervised machine learning methodology, and incorporated routine laboratory, demographic, biometric, and admission data. Area under the receiver operating characteristic curve (AUC), calibration and decision curves were compared between clinician estimates and the model predictions. RESULTS: Within 45 days following hospital admission, 229 (25%) of 911 patients died. The model performed better than the clinician estimates (AUC 0.834 vs. 0.753, p < 0.0001). Integrating clinician predictions with the model's estimates further increased the AUC to 0.853 (p < 0.0001). Clinicians overestimated risk whereas the model was extremely well-calibrated. The model demonstrated net benefit over a wide range of threshold probabilities. CONCLUSION: The inpatient prognosis at admission model is a robust tool to assist clinical providers in evaluating mortality risk, and it has recently been implemented in the electronic medical record at our institution to improve end-of-life care planning for hospitalized cancer patients.

Analytical Validation and Performance Characteristics of Molecular Serum Biomarkers, miR-371a-3p and miR-372-3p, for Male Germ Cell Tumors, in a Clinical Laboratory Setting.

Detection of serum embryonic miRNAs miR-371a-3p and miR-372-3p has been proposed to aid in diagnosis, prognosis, and management of patients with testicular germ cell tumors (GCTs). This study describes the analytical validation and performance of a laboratory-developed test to detect these miRNA targets by stem loop real-time quantitative RT-PCR (RT-qPCR) in serum from patients with GCTs. The assay was standardized using an exogenous spike-in control of nonhuman miRNA from Caenorhabditis elegans (cel-miR-39-3p) to assess extraction efficiency, and an endogenous housekeeping miRNA, miR-30b-5p, to control for miRNA normalization. miRNA results were expressed as relative expression level, using the comparative threshold cycle method (2ΔΔCT). Analytical sensitivity of miR-371a-3p and miR-372-3p was 12.5 and 1.25 copies/µL, respectively. Clinical accuracy was evaluated using GCT patients with (n = 34) and without (n = 17) active disease. Positive/negative cutoffs and indeterminate findings were established on the basis of results from healthy volunteers (n = 25) and assay precision. miR-371a-3p and miR-372-3p exhibited a sensitivity of 81.8% and 87.5%, respectively, and a specificity of 100% and 94%, respectively, and an area under the receiver operating characteristic curve of 0.93 and 0.95, respectively. Taken together, RT-qPCR testing for serum miR-371a-3p and miR-372-3p represents a robust, sensitive, and specific clinical assay to aid in the clinical management of patients with GCT.

Association of Antineoplastic Therapy With Decreased SARS-CoV-2 Infection Rates in Patients With Cancer.

Importance: Novel therapies for SARS-CoV-2 infection are urgently needed. Antineoplastic compounds that target cellular machinery used by SARS-CoV-2 for entry and replication, including angiotensin-converting enzyme 2 (ACE2), may disrupt SARS-CoV-2 activity. Objectives: To determine whether patients with cancer treated with potential ACE2-lowering antineoplastic compounds exhibit lower SARS-CoV-2 infection rates. Design, Setting, and Participants: We used the Library of Integrated Network-Based Cellular Signatures database to identify antineoplastic compounds associated with decreased ACE2 gene expression across cell lines. We then evaluated a retrospective cohort of 1701 patients who were undergoing antineoplastic therapy at Memorial Sloan Kettering Cancer Center in New York, New York, during the COVID-19 pandemic to determine if treatment with an ACE2-lowering antineoplastic was associated with a decreased odds ratio (OR) of SARS-CoV-2 infection. Patients included in the analysis underwent active treatment for cancer and received a SARS-CoV-2 test between March 10 and May 28, 2020. Main Outcome and Measure: The association between potential ACE2-lowering antineoplastic treatment and a positive SARS-CoV-2 test. Results: In the cohort of 1701 patients, SARS-CoV-2 infection rates were determined for 949 (55.8%) female and 752 (44.2%) male patients (mean [SD] age, 63.1 [13.1] years) with diverse cancers receiving antineoplastic therapy. In silico analysis of gene expression signatures after drug treatment identified 91 compounds associated with downregulation of ACE2 across cell lines. Of the total cohort, 215 (12.6%) patients were treated with 8 of these compounds, including 3 mTOR/PI3K inhibitors and 2 antimetabolites. In a multivariable analysis of patients who received an ACE2-lowering antineoplastic adjusting for confounders, 15 of 215 (7.0%) patients had a positive SARS-CoV-2 test compared with 191 of 1486 (12.9%) patients who received other antineoplastic therapies (OR, 0.53; 95% CI, 0.29-0.88). Findings were confirmed in additional sensitivity analyses including cancer type, steroid use, and a propensity-matched subcohort. Gemcitabine treatment was associated with reduced SARS-CoV-2 infection (OR, 0.42; 95% CI, 0.17-0.87). Conclusions and Relevance: In this cohort study, in silico analysis of drug-associated gene expression signatures identified potential ACE2-lowering antineoplastic compounds, including mTOR/PI3K inhibitors and antimetabolites. Patients who received these compounds exhibited statistically significantly lower rates of SARS-CoV-2 infection compared with patients given other antineoplastics. Further evaluation of the biological and clinical anti-SARS-CoV-2 properties of identified antineoplastic compounds is warranted.

Predictors of Humoral Response to SARS-CoV-2 Vaccination after Hematopoietic Cell Transplantation and CAR T-cell Therapy.

Cellular therapies including allogeneic hematopoietic cell transplant (allo-HCT) and autologous hematopoietic cell transplant (auto-HCT) and chimeric antigen receptor (CAR) T-cell therapy render patients severely immunocompromised for extended periods after therapy, and data on responses to COVID-19 vaccines are limited. We analyzed anti-SARS-CoV-2 spike IgG Ab (spike Ab) titers and neutralizing Ab among 217 recipients of cellular treatments (allo-HCT, n = 149; auto-HCT, n = 61; CAR T-cell therapy, n = 7). At 3 months after vaccination, 188 patients (87%) had positive spike Ab levels and 139 (77%) had positive neutralization activity compared with 100% for both in 54 concurrent healthy controls. Time from cellular therapy to vaccination and immune recovery post-cellular therapy were associated with response. Vaccination against COVID-19 is an important component of post-cellular therapy care, and predictors of quantitative and qualitative response are critical in informing clinical decisions about optimal timing of vaccines and the requirement for booster doses. Significance: Identifying predictors of response to vaccination against SARS-CoV-2 in patients following cellular therapy is critical to managing this highly vulnerable patient population. To date, this is the most comprehensive study evaluating quantitative and qualitative responses to vaccination, providing parameters most predictive of response and potentially informing booster vaccination strategies.See related article by Chung et al., p. 568. This article is highlighted in the In This Issue feature, p. 549.

Disease- and Therapy-Specific Impact on Humoral Immune Responses to COVID-19 Vaccination in Hematologic Malignancies.

Coronavirus disease-19 (COVID-19) vaccine response data for patients with hematologic malignancy, who carry high risk for severe COVID-19 illness, are incomplete. In a study of 551 hematologic malignancy patients with leukemia, lymphoma, and multiple myeloma, anti-SARS-CoV-2 spike IgG titers and neutralizing activity were measured at 1 and 3 months from initial vaccination. Compared with healthy controls, patients with hematologic malignancy had attenuated antibody titers at 1 and 3 months. Furthermore, patients with hematologic malignancy had markedly diminished neutralizing capacity of 26.3% at 1 month and 43.6% at 3 months, despite positive seroconversion rates of 51.5% and 68.9% at the respective time points. Healthy controls had 93.2% and 100% neutralizing capacity at 1 and 3 months, respectively. Patients with leukemia, lymphoma, and multiple myeloma on observation had uniformly blunted responses. Treatment with Bruton tyrosine kinase inhibitors, venetoclax, phosphoinositide 3-kinase inhibitors, anti-CD19/CD20-directed therapies, and anti-CD38/B-cell maturation antigen-directed therapies substantially hindered responses, but single-agent immunomodulatory agents did not. Significance: Patients with hematologic malignancy have compromised COVID-19 vaccine responses at baseline that are further suppressed by active therapy, with many patients having insufficient neutralizing capacity despite positive antibody titers. Refining vaccine response parameters is critical to guiding clinical care, including the indication for booster vaccines, for this vulnerable population.See related article by Tamari et al., p. 577. This article is highlighted in the In This Issue feature, p. 549.

Clonal hematopoiesis is associated with risk of severe Covid-19.

Acquired somatic mutations in hematopoietic stem and progenitor cells (clonal hematopoiesis or CH) are associated with advanced age, increased risk of cardiovascular and malignant diseases, and decreased overall survival. These adverse sequelae may be mediated by altered inflammatory profiles observed in patients with CH. A pro-inflammatory immunologic profile is also associated with worse outcomes of certain infections, including SARS-CoV-2 and its associated disease Covid-19. Whether CH predisposes to severe Covid-19 or other infections is unknown. Among 525 individuals with Covid-19 from Memorial Sloan Kettering (MSK) and the Korean Clonal Hematopoiesis (KoCH) consortia, we show that CH is associated with severe Covid-19 outcomes (OR = 1.85, 95%=1.15-2.99, p = 0.01), in particular CH characterized by non-cancer driver mutations (OR = 2.01, 95% CI = 1.15-3.50, p = 0.01). We further explore the relationship between CH and risk of other infections in 14,211 solid tumor patients at MSK. CH is significantly associated with risk of Clostridium Difficile (HR = 2.01, 95% CI: 1.22-3.30, p = 6×10-3) and Streptococcus/Enterococcus infections (HR = 1.56, 95% CI = 1.15-2.13, p = 5×10-3). These findings suggest a relationship between CH and risk of severe infections that warrants further investigation.

The New York State SARS-CoV-2 Testing Consortium: Regional Communication in Response to the COVID-19 Pandemic.

The COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2, created an unprecedented need for comprehensive laboratory testing of populations, in order to meet the needs of medical practice and to guide the management and functioning of our society. With the greater New York metropolitan area as an epicenter of this pandemic beginning in March 2020, a consortium of laboratory leaders from the assembled New York academic medical institutions was formed to help identify and solve the challenges of deploying testing. This report brings forward the experience of this consortium, based on the real-world challenges which we encountered in testing patients and in supporting the recovery effort to reestablish the health care workplace. In coordination with the Greater New York Hospital Association and with the public health laboratory of New York State, this consortium communicated with state leadership to help inform public decision-making addressing the crisis. Through the length of the pandemic, the consortium has been a critical mechanism for sharing experience and best practices in dealing with issues including the following: instrument platforms, sample sources, test performance, pre- and post-analytical issues, supply chain, institutional testing capacity, pooled testing, biospecimen science, and research. The consortium also has been a mechanism for staying abreast of state and municipal policies and initiatives, and their impact on institutional and laboratory operations. The experience of this consortium may be of value to current and future laboratory professionals and policy-makers alike, in dealing with major events that impact regional laboratory services.

Chemotherapy and COVID-19 Outcomes in Patients With Cancer.

PURPOSE: Coronavirus-2019 (COVID-19) mortality is higher in patients with cancer than in the general population, yet the cancer-associated risk factors for COVID-19 adverse outcomes are not fully characterized. PATIENTS AND METHODS: We reviewed clinical characteristics and outcomes from patients with cancer and concurrent COVID-19 at Memorial Sloan Kettering Cancer Center until March 31, 2020 (n = 309), and observed clinical end points until April 13, 2020. We hypothesized that cytotoxic chemotherapy administered within 35 days of a COVID-19 diagnosis is associated with an increased hazard ratio (HR) of severe or critical COVID-19. In secondary analyses, we estimated associations between specific clinical and laboratory variables and the incidence of a severe or critical COVID-19 event. RESULTS: Cytotoxic chemotherapy administration was not significantly associated with a severe or critical COVID-19 event (HR, 1.10; 95% CI, 0.73 to 1.60). Hematologic malignancy was associated with increased COVID-19 severity (HR, 1.90; 95% CI, 1.30 to 2.80). Patients with lung cancer also demonstrated higher rates of severe or critical COVID-19 events (HR, 2.0; 95% CI, 1.20 to 3.30). Lymphopenia at COVID-19 diagnosis was associated with higher rates of severe or critical illness (HR, 2.10; 95% CI, 1.50 to 3.10). Patients with baseline neutropenia 14-90 days before COVID-19 diagnosis had worse outcomes (HR, 4.20; 95% CI, 1.70 to 11.00). Findings from these analyses remained consistent in a multivariable model and in multiple sensitivity analyses. The rate of adverse events was lower in a time-matched population of patients with cancer without COVID-19. CONCLUSION: Recent cytotoxic chemotherapy treatment was not associated with adverse COVID-19 outcomes. Patients with active hematologic or lung malignancies, peri-COVID-19 lymphopenia, or baseline neutropenia had worse COVID-19 outcomes. Interactions among antineoplastic therapy, cancer type, and COVID-19 are complex and warrant further investigation.

Clonal hematopoiesis is associated with risk of severe Covid-19.

Acquired somatic mutations in hematopoietic stem and progenitor cells (clonal hematopoiesis or CH) are associated with advanced age, increased risk of cardiovascular and malignant diseases, and decreased overall survival. 1-4 These adverse sequelae may be mediated by altered inflammatory profiles observed in patients with CH. 2,5,6 A pro-inflammatory immunologic profile is also associated with worse outcomes of certain infections, including SARS-CoV-2 and its associated disease Covid-19. 7,8 Whether CH predisposes to severe Covid-19 or other infections is unknown. Among 515 individuals with Covid-19 from Memorial Sloan Kettering (MSK) and the Korean Clonal Hematopoiesis (KoCH) consortia, we found that CH was associated with severe Covid-19 outcomes (OR=1.9, 95%=1.2-2.9, p=0.01). We further explored the relationship between CH and risk of other infections in 14,211 solid tumor patients at MSK. CH was significantly associated with risk of Clostridium Difficile (HR=2.0, 95% CI: 1.2-3.3, p=6×10 -3 ) and Streptococcus/Enterococcus infections (HR=1.5, 95% CI=1.1-2.1, p=5×10 -3 ). These findings suggest a relationship between CH and risk of severe infections that warrants further investigation.

Measurement of the DNA alkylating agents busulfan and melphalan in human plasma by mass spectrometry.

Busulfan and melphalan are cytotoxic DNA alkylating agents that are used in many hematopoietic stem cell transplantation (HCT) conditioning regimens. We report the development of an assay using turbulent flow liquid chromatography (TFLC) and tandem mass spectrometry to simultaneously measure the concentration of busulfan (Bu) and melphalan (Mel) in human plasma. The method involves precipitating proteins in the plasma specimen with an organic solvent containing deuterated internal standards of both compounds. Following centrifugation, an aliquot of the supernatant was injected into the TFLC mass spectrometry system operated in the positive ion mode. The analytical measurement range for both compounds was 10-5000 ng/mL, and with validated dilutions the reportable range was extended to 25,000 ng/mL. Intra-day and inter-day (n = 20 day) precision studies showed a coefficient of variation (CV) of <7% at several concentrations across the measurement range. To determine accuracy recovery studies were performed at several concentrations spanning the measurement range. Recoveries for both compounds were between 98 and 103%. Additionally, busulfan was compared with an existing assay and showed excellent correlation. Experiments were conducted to rule out matrix effects, carryover and interference from endogenous substances. The validated clinically reportable range (CRR) and assay precision will allow this assay to be used clinically to monitor and adjust Mel and Bu levels to ensure better therapeutic outcomes and also to support clinical trials aimed at better defining therapeutic ranges.

Data to support a simultaneous testosterone and estradiol assay in serum by LC-MS/MS.

A very sensitive LC-MS/MS assay was developed implementing a liquid-liquid extraction step followed by mass spectrometry which was operated in both positive and negative ion modes. The assay was calibrated with readily available commercial calibrators and compared with international reference standards. This data is also presented in "Sensitive Simultaneous Quantitation of Testosterone and Estradiol in Serum by LC-MS/MS without Derivatization and Comparison with the CDC HoSt Program" (Schofield et al., 2017). This article includes the comparison of the LC-MS/MS assay with a commonly available chemiluminescencent immunoassay for the quantitation of both estradiol and testosterone. In addition we show baseline separation of estradiol and testosterone from other structurally related and/or isobaric compounds that could potentially interfere with the assay. In addition, various calibrator materials were tested and compared with internationally-recognized reference materials.