febrile neutropaenia

quick recognition

• febrile patient with recent chemotherapy (highest risk 1–2 weeks post-chemo, nadir ANC at days 12–14)
• screening question: “any chemotherapy or anti-cancer treatment in the last 6 weeks?” — if yes, assume neutropaenia until proven otherwise
• fever may be the only sign of infection — neutropaenic patients lack the inflammatory response to localise infection (no abscess formation, minimal CXR infiltrate, no pyuria)
• absence of localising signs does not mean absence of infection

when to suspect

severity of neutropaenia

ANC	severity	infection risk
1.0–1.5 × 10⁹/L	mild	low — usually safe
0.5–1.0 × 10⁹/L	moderate	increasing risk
<0.5 × 10⁹/L	severe	high risk of inadequate total body neutrophils
<0.1 × 10⁹/L	profound	highest risk — prophylaxis indicated if >7 days expected

Risk amplifiers: duration of neutropaenia (>7 days worse), concurrent immunosuppression (chemotherapy, rituximab, T-cell suppressants), mucosal barrier injury.

Duffy null associated neutropaenia

• genetic variant (Duffy antigen/receptor for chemokines) — neutrophils sequester in spleen rather than circulating peripherally → lower measured ANC but normal total body neutrophil count and immune function
• provides evolutionary advantage against Plasmodium vivax malaria
• prevalence: 80–100% in West Africa, ~67% of self-identified Black individuals in North America
• test for Duffy null phenotype when ANC 1.0–1.5 × 10⁹/L in patients of African or Middle Eastern ancestry
• these patients do not have increased infection risk and should not be treated as immunocompromised

diagnosis / investigations

first question: isolated neutropaenia or pancytopaenia?

• pancytopaenia → broader differential including marrow infiltration, aplastic anaemia, MDS → bone marrow biopsy usually indicated
• isolated neutropaenia → haematologic malignancies are uncommon causes; bone marrow biopsy usually NOT recommended

workup of neutropaenia

History drives the diagnosis more than labs in isolated neutropaenia:

• medications — most common cause (see below)
• comorbidities — autoimmune diseases, malabsorption (coeliac, gastric sleeve), nutritional deficiencies (B12, folate, copper)
• pattern — chronic neutropaenia often less concerning than acute
• severity — urgent haematology referral for any new ANC <0.5 × 10⁹/L

medication-induced neutropaenia

type	mechanism	onset	management	examples
type 1	dose/duration dependent	gradual	dose reduction may suffice	mycophenolate, azathioprine, ganciclovir, linezolid
type 2	immune-mediated (antibody to drug-neutrophil complex)	abrupt, severe	must stop permanently — cannot rechallenge	clozapine, methimazole, PTU, dapsone, sulfasalazine

febrile neutropaenia workup (within 15 minutes of triage)

• cultures: minimum 2 sets — 1 peripheral + 1 from each CVC lumen
• source assessment: oropharynx (mucositis), catheter sites, lungs, perianal inspection
  • no DRE — risk of mucosal tear and bacterial translocation
• bloods: FBC, differential, electrolytes, creatinine, LDH, lactate, liver function
• imaging: CXR has low sensitivity in neutropaenia — low-dose chest CT preferred if respiratory symptoms
• urine: culture only if urinary symptoms or abnormal urinalysis — pyuria may be absent in neutropaenia but routine urine culture is no longer recommended

classification of neutropaenic fever syndromes

1. microbiologically documented infection — identified pathogen with source (most useful for guiding targeted therapy)
2. clinically documented infection — clear focus (e.g. pneumonia on imaging, cellulitis) without pathogen
3. unexplained fever — most common scenario (~60–70%); SIRS without identified source

risk stratification

MASCC score

Determines site of care — inpatient vs. outpatient.

characteristic	weight
burden of illness: no/mild symptoms	5
burden of illness: moderate symptoms	3
no hypotension (SBP ≥90 mmHg)	5
no COPD	4
solid tumour or no prior fungal infection	4
no dehydration	3
outpatient at onset of fever	3
age <60 years	2

• ≥21: low risk — outpatient management candidate (PO ciprofloxacin + amoxicillin-clavulanate)
• <21: high risk — inpatient admission required

CISNE score is an alternative validated tool for identifying low-risk patients in the ED.

who is high risk?

• haematologic malignancy (leukaemia, lymphoma) — “double hit” to marrow from cancer + chemotherapy → prolonged, severe neutropaenia
• expected neutropaenia >7 days
• significant comorbidities, haemodynamic instability
• solid tumour patients receiving cyclical chemotherapy are generally lower risk — functional marrow, shorter neutropaenia duration

management

step 1: empirical antibiotics within 60 minutes

Standard first-line — antipseudomonal monotherapy:

agent	dose	notes
imipenem-cilastatin	500 mg IV q6h	lowers seizure threshold — caution in CNS disease
Piperacillin-Tazobactam	4.5 g IV q6h	3.375 g is insufficient for FN
cefepime	2 g IV q8h	common first-line at many Canadian centres
meropenem	1 g IV q8h	reserve for ESBL history or deterioration

Severe penicillin/cephalosporin allergy:

• Vancomycin + aztreonam (preferred) or vancomycin + ciprofloxacin 400 mg IV q8h — consult ID/allergy

step 2: when to add vancomycin

Vancomycin is not standard first-line. Add only if:

1. haemodynamic instability / septic shock
2. known MRSA colonisation and infection source likely MRSA (gram-positive cocci in blood, pneumonia, soft tissue, severe mucositis)
3. clinically apparent line infection (inflamed tunnel/exit site)
4. gram-positive cocci on preliminary blood culture

step 3: resistant organism considerations

• VRE history → add linezolid or daptomycin
• ESBL history → early escalation to carbapenems
• KPC (carbapenemase) → consult ID (ceftazidime-avibactam, cefiderocol, or colistin)

step 4: antifungal coverage

Trigger: persistent fever ≥96 hours (4–7 days) despite broad-spectrum antibiotics in high-risk patients (ANC ≤0.1 × 10⁹/L for ≥7 days, haematologic malignancies especially AML).

Two strategies:

• pre-emptive (preferred if rapid diagnostics available): galactomannan + β-D-glucan + chest CT → initiate antifungal only if positive
• empiric: start antifungal if no rapid diagnostics

Agents (mould-active):

• liposomal amphotericin B 3 mg/kg/day
• voriconazole (if aspergillosis suspected)
• caspofungin 70 mg load → 50 mg daily

prophylaxis in prolonged neutropaenia

Indicated when ANC ≤0.1 × 10⁹/L expected for >7 days (typically haematologic malignancy patients on chemotherapy):

• antibacterial: fluoroquinolone (ciprofloxacin or levofloxacin — pseudomonal coverage)
• antifungal: posaconazole or isavuconazole (yeast + mould coverage)

reassessment and escalation (72–96 hours)

persistent fever, stable patient

• do not switch antibiotics solely for persistent fever if clinically stable
• repeat blood cultures only if clinical deterioration or new fever spike — routine repeats discouraged
• consider chest/abdominal CT to rule out occult source

clinical deterioration

• escalate to meropenem (if on cefepime/pip-taz) ± vancomycin
• reassess for invasive fungal infection
• consider ICU transfer

de-escalation and duration

• documented infection: treat for standard duration of the specific infection (e.g. pseudomonal bacteraemia per bacteraemia guidelines, not as unexplained FN)
• unexplained fever (FUO): stop after 3–5 days afebrile + stable
• most patients are on antibiotics for 7–10 days total (median time to defervescence ~5 days + additional days afebrile)
• gut mucosal recovery from cytotoxic therapy coincides with this timeline — mucositis → bacterial translocation risk resolves over ~10 days

neutrophil recovery timelines

cause	expected recovery	notes
viral infection	10–14 days	self-limited
immune-mediated drug (type 2)	10–14 days after stopping	rapid once drug cleared — depends on drug half-life
dose-dependent drug (type 1)	3–4 weeks	nadir at 14–21 days post-exposure
autoimmune disease	variable	paradox: immunosuppressive treatment for the underlying disease may improve neutropaenia
MDS	variable/may not recover	even with treatment

It takes 7–10 days to produce a mature neutrophil from haematopoietic stem cell — sets the floor for recovery from any cause.

special populations

catheter-related infections

organism	line management
coagulase-negative staph (CoNS)	retain line, treat systemically
S. aureus, Candida, Pseudomonas, mycobacteria	prompt removal recommended
tunnel or pocket infection	remove line

In severe thrombocytopaenia or coagulopathy, removal may be deferred until haemostatically safe — but source control is critical for these organisms.

viral considerations

In patients with respiratory symptoms/infiltrates — send multiplex respiratory PCR. Bronchoscopy (BAL) is mandatory if infiltrates suspected to be invasive fungal infection.

G-CSF in febrile neutropaenia

• not routinely recommended for treatment of established FN
• meta-analysis of RCTs: G-CSF decreased hospitalisation time and neutropaenia duration but no improvement in overall mortality or infection-related mortality
• consider in high-risk patients: prolonged neutropaenia >10 days, profound neutropaenia <0.1 × 10⁹/L, age >65, severe sepsis, invasive fungal disease

what NOT to do

• delay antibiotics waiting for culture results or ANC confirmation — treat empirically within 60 minutes
• add vancomycin routinely — no mortality benefit, drives resistance
• “double-cover” Pseudomonas (β-lactam + aminoglycoside) routinely — not indicated unless septic shock or high local resistance
• switch antibiotics solely for persistent fever in a stable patient
• repeat blood cultures routinely without clinical deterioration
• perform DRE — mucosal tear → translocation risk
• use 3.375 g pip-taz for FN — insufficient dose; use 4.5 g q6h
• give G-CSF routinely for FN — no mortality benefit

key trials summary

trial / source	year	finding
Klastersky, JCO. 2000	2000	MASCC score validated for identifying low-risk FN patients suitable for outpatient management
HOW LONG (2017)	2017	antibiotics discontinued after 72h apyrexia regardless of ANC — no increase in adverse outcomes