Approach to the Critical Patient

Immediate priorities

Airway, breathing, circulation assessment

Critical branching decisions

Reactive leukemoid reaction vs. hematologic malignancy

Monitoring and escalation targets

Monitoring bundle for leukemoid reaction

Immediate consults

Consultation triggers

History

Presenting symptoms

Onset and duration of symptoms

Source-directed symptom review

Respiratory symptoms

Abdominal symptoms

Urinary symptoms

Wound or skin infection symptoms

Constitutional alarm symptoms

B symptoms suggesting malignancy

Medication and exposure history

Medications causing leukocytosis

Toxic exposures

Risk factor history

High-risk conditions

Family and past medical history

Prior CBC values and baseline WBC

History of malignancy

Family history

Chronic conditions

Physical Exam

Vital signs

Hemodynamic assessment

Head, eyes, ears, nose, throat

Oral cavity and oropharynx

Fundoscopic examination

Lymph nodes

Lymphadenopathy distribution

Abdominal examination

Splenomegaly

Hepatomegaly

Abdominal tenderness

Skin and integument

Petechiae and purpura

Leukemia cutis

Wound infections, cellulitis, pressure ulcers

Pulmonary examination

Consolidation findings

Neurological examination

Mental status assessment

Musculoskeletal

Differential Diagnosis

Hematologic malignancies

Chronic myeloid leukemia (CML) — ICD-10 C92.1

Acute myeloid leukemia (AML) — ICD-10 C92.0

Acute lymphoblastic leukemia (ALL) — ICD-10 C91.0

Chronic neutrophilic leukemia (CNL) — ICD-10 C92.2

Myeloproliferative neoplasms

Myeloproliferative neoplasms (MPN) — ICD-10 D47.1

Pediatric-specific diagnoses

Juvenile myelomonocytic leukemia (JMML) — ICD-10 C93.3

Transient abnormal myelopoiesis (TAM) — ICD-10 D75.89

Reactive leukocytosis

Leukemoid reaction (LR) — ICD-10 D72.823

Hyperleukocytosis with leukostasis

Leukostasis syndrome — ICD-10 D72.829

Laboratory Tests

Initial workup

Complete blood count with manual differential

Peripheral blood smear

Manual smear review — cornerstone of initial evaluation

Inflammatory markers

C-reactive protein (CRP)

Metabolic panel and organ function

Comprehensive metabolic panel

LDH and uric acid

Microbiological testing

Blood cultures

Coagulation studies

DIC screen

Leukocyte alkaline phosphatase score

LAP score — historically the key differentiator

Molecular and cytogenetic testing

BCR-ABL1 by FISH or RT-PCR

Flow cytometry

Myeloid mutation panel (NGS)

Bone marrow aspirate and biopsy

Sepsis biomarkers

Lactate

Diagnostic Tests

Scoring Systems

No validated scoring system specifically for leukemoid reaction diagnosis

Sepsis scoring in context of LR

Sequential Organ Failure Assessment (SOFA)

qSOFA for initial risk stratification

MRI

MRI indications in leukemoid reaction

CT

CT chest

CT abdomen and pelvis

CT head

Ultrasound

Spleen size assessment

Abdominal ultrasound for infection source

Bedside point-of-care ultrasound (POCUS)

Disposition

Admission indications

Criteria requiring inpatient admission

ICU-level care

ICU admission triggers

Observation-level care

Appropriate for observation unit

Discharge criteria

Safe discharge requirements

Specialist consultation triggers

Hematology/oncology

Infectious disease

Surgery

Follow-up plan

Post-discharge monitoring

Treatment

Underlying cause directed therapy

No specific treatment targets the leukemoid reaction itself

Sepsis management (most common trigger)

Fluid resuscitation

Empiric antibiotics

Vasopressors

Hemorrhage management

For LR from severe hemorrhage

Drug-induced leukocytosis management

Offending agent discontinuation

Leukostasis management

Emergency cytoreduction for symptomatic hyperleukocytosis

Tumor lysis syndrome prevention

If hematologic malignancy suspected or confirmed

Source control

Surgical and procedural interventions

Special Populations

Pregnancy

Physiologic leukocytosis in pregnancy

Obstetric causes of LR

Medication considerations

Workup modifications

Geriatric

Epidemiology in older adults

Atypical presentations

Treatment modifications

Goals of care

Pediatrics

Epidemiology

Etiology differences from adults

Diagnostic pearls in children

Neonatal considerations

Background

Epidemiology

Incidence and prevalence

Mortality data

Age demographics

Pathophysiology

Mechanism of reactive leukocytosis

Neutrophil morphology in LR

Leukocyte alkaline phosphatase (LAP) in reactive states

Leukostasis pathophysiology

Therapeutic Considerations

Treatment philosophy

Antibiotic stewardship in LR

Steroid considerations

Cytoreduction threshold and approach

Transfusion caution

Patient Discharge Instructions

copy discharge instructions

What is a leukemoid reaction?

Your diagnosis and treatment plan

Follow-up instructions

Warning signs — return to emergency immediately for

Lifestyle guidance

Important notes about your ongoing testing

References

Guidelines and key sources

Sakka V, Tsiodras S, Giamarellos-Bourboulis EJ, Giamarellou H

Potasman I, Grupper M

Riley LK, Rupert J

Landmark studies and disease classification

Iyengar V, Meyer A, Stedman E, et al

George TI

Hoofien A, Yarden-Bilavski H, Ashkenazi S, et al

Society guidelines

National Comprehensive Cancer Network (NCCN)

Surviving Sepsis Campaign 2021

Baral MR, Bhandari S

Bociek RG, Lunning M