Leukocytosis

• Leukocytosis isn’t specific nor sensitive to bacterial infection, the following conditions can cause leukocytosis that can be severe even in the absence of infections:
  • DKA is commonly associated with leukocytosis which can be severe but improves quickly with DKA treatment.
  • Acute pancreatitis can cause leukocytosis which can be severe, no antibiotics are required regardless of the type (interstitial or necrotizing) or disease severity, unless there is an associated bacterial infection.
  • Trauma and fractures, also commonly produce leukocytosis
  • All kinds of shocks can cause leukocytosis which can be severe
  • Postoperative patients, regardless of what kind of surgery, these patients usually receive prophylactic antibiotics, and leukocytosis usually develops the next day and gets better afterward, do not suspect a postoperative infection relying solely on leukocytosis
  • Smoking, smoking is one of the most common causes of leukocytosis that is usually mild, severe leukocytosis shouldn’t be attributed to smoking, other causes should be sought
  • Medications, most commonly steroid use, less commonly lithium, all-trans retinoic acid, catecholamine use, and of course, G-CSF like filgrastim used to treat neutropenia, all can lead to leukocytosis, steroids are the most commonly encountered in clinical practice, correlate between the onset of leukocytosis and administration of medications
• In general, any stress on the body can produce leukocytosis.
• All these conditions produce neutrophilic leukocytosis, CLL, on the other hand, produces lymphocytic leukocytosis.

Bilateral lung infiltrates

• Bilateral lung infiltrates on CXR can be misdiagnosed as bilateral PNA -which still can be true- but the following non-infectious causes should be considered in the differential diagnosis:
  • Patients with pulmonary edema may develop bilateral infiltrates on chest X-ray and can also present with leukocytosis. However, they typically show signs of fluid overload, have elevated BNP levels, and do not have a fever. Shortness of breath is the most prominent symptom. Remember that they may or may not have a history of CHF. These patients require diuresis, not antibiotics.
  • Patients with pulmonary fibrosis and other interstitial lung diseases often present with bilateral interstitial infiltrates. These patients are typically on home oxygen, most already have a known diagnosis, and usually have a normal BNP with no associated fever. Always compare their current chest X-ray or CT with previous images for proper assessment.

Bilateral lower extremities erythema

• Bilateral lower extremity erythema is often misdiagnosed as cellulitis, but true bilateral symmetric cellulitis is rare. The following conditions are frequently mistaken for cellulitis and treated as such:
  • Venous or stasis dermatitis patients are commonly misdiagnosed as having cellulitis, these patients have chronic LE swelling, usually bilateral but can be unilateral, and scaling and erosion can be present as well.
  • Erythema nodosum is also sometimes misdiagnosed as cellulitis, EN causes erythematous, usually tender, nonulcerated, immobile nodules on the bilateral shins areas.
  • Bilateral DVT, r/o DVT if lower extremity swelling with erythema is present.

Acute bronchitis, sinusitis, and acute asthma exacerbation

• Acute bronchitis is usually caused by a viral infection, with the primary symptom being a dry cough. These patients typically do not experience shortness of breath, tachypnea, or fever. If a chest X-ray (CXR) is performed, it is often clear or unchanged from the patient’s baseline, although the baseline CXR may already be abnormal. However, this does not apply to patients with COPD when they develop COPD exacerbation due to acute bronchitis, in which case antibiotics are indicated.
• Acute asthma exacerbation: Patients typically present with tachypnea, shortness of breath, wheezing, and chest tightness. Despite these symptoms, their oxygen levels are usually normal. Antibiotics are not required unless there is a coexisting pneumonia. This is in contrast to COPD exacerbation where antibiotics are usually recommended especially in moderate to severe exacerbations.

• Acute sinusitis: The key symptoms include nasal congestion, nasal discharge, and headache. Symptomatic management is typically provided, and antibiotics are only prescribed if there is no improvement by day 7, the patient is unlikely to follow up, or if symptoms worsen during the observation period.

Urine colonization or a contaminated urine sample

• UTI = Symptoms + Positive urinalysis (Treat with antibiotics)
• No symptoms + Positive urine culture (urinalysis may be positive) = Asymptomatic bacteriuria ( No antibiotics indicated), Exceptions to this are:
  • Pregnant patients must be treated whether symptomatic or not.
  • Patients undergoing urologic procedures whether symptomatic or not.

Positive urinalysis (For diagnosing UTI purposes) = The presence of >= 10 cells/microL leukocytes in urine.

Contaminated blood cultures misdiagnosed as true bacteremia

• Suspect a contaminated blood culture if:
  • The bacteria isolated from the blood is inconsistent with the suspected infection, for example, a patient with UTI growing gram-negative rods in urine culture and gram-positive cocci in blood culture, here the blood culture is likely a contaminant
  • The patient is clinically stable with a low suspicion of bacterial infection.
  • Gram-positive cocci (whether in clusters or chains) or gram-positive rods were reported in one set only, and the second one remained negative. However, it isn’t uncommon to have both sets contaminated.
• In these situations, it is better to withhold antibiotics and wait for the final culture results, or you can repeat the blood cultures. In most cases, the cultures will eventually grow coagulase-negative staphylococci.

Isolated fever episodes

• Don’t jump and start antibiotics every time you get called about a febrile patient unless the patient is immunosuppressed including those with neutropenia.
• Body core temperature:
  • Normal:  35.3 to 37.7°C (95.5 to 99.9°F).
  • A low-grade fever: 37.7- 38°C (99.9-100.4°F).
  • High-grade: > 38°C (100.4°F)
• In low-grade fever (in immunocompetent patients), it’s reasonable to watch the patient and look for non-infectious causes of fever.

On the other hand, a temperature above 38 or 100.4 is considered a high-grade fever, if recurrent, initiate infection w/u then start empiric antibiotics if infection w/u is negative and cultures remain negative then consider stopping these antibiotics.