Lower respiratory Cough, chest pain, dyspnea, sputum Tachypnea, crackles, wheezing, localized diminished breath sounds, tract production, cyanosis intercostal retractions
Gastrointestinal Nausea, vomiting, diarrhea, abdominal pain Hypoactive or hyperactive bowel sounds, abdominal tenderness (focal tract (focal or diffuse), anorexia, weight loss or generalized), hematochezia
Liver Anorexia, vomiting, dark urine, light stools Jaundice, hepatomegaly, hepatic tenderness, bleeding diatheses, coma
Genitourinary tract Dysuria, frequency, urgency, flank or Costovertebral angle or suprapubic tenderness, cervical motion and suprapubic pain, vaginal discharge adnexal tenderness
Central nervous Lethargy, irritability, headache, neck stiffness, Nuchal rigidity, Kernig sign, Brudzinski sign, bulging fontanelle, focal system seizures neurologic deficits, altered mental status, coma
Musculoskeletal Limp, bone pain, limited function Local swelling, erythema, warmth, limited range of motion, point bone (pseudoparalysis) tenderness, joint line tenderness *Fever usually accompanies infection as a systemic manifestation.
of trichinellosis, the pulmonary phases of ascariasis and hookworm infection (eosinophilic pneumonia), and the hepatic and central nervous system phases of visceral larva migrans.
Other common screening tests include urinalysis for urinary tract infections, transaminases for liver function, and lumbar puncture for evaluation of the cerebrospinal fluid if there is concern for meningitis or encephalitis (see Chapters 100 and 101). Various tests may help distinguish viral versus bacterial infection, but definitive diagnosis requires identifying the agent by culture or another test, such as polymerase chain reaction.
Cultures are the mainstay of diagnosis of many infections. Blood cultures are sensitive and specific for bacteremia, which may be primary or secondary to a focal infection (osteomyelitis, gastroenteritis, urinary tract, and endocarditis). Urine cultures are important to confirm urinary tract infection, which may be occult in young infants. Cultures should be obtained with every lumbar puncture, aspiration, or biopsy of other fluid collections or masses. Specific types of cultures (bacterial, fungal, viral, or mycobacterial) are guided by the clinical problem. Tissue culture techniques are used to identify viruses and intracellular bacterial pathogens.
Antibiotics often are begun before a definitive diagnosis is established, complicating the ability to rely on subsequent cultures for microbiologic diagnosis (see Chapter 95). Although persistent or progressive symptoms, despite antibiotic treatment, may indicate the need to change the regimen, more frequently this indicates the need to stop all antibiotics to facilitate definitive diagnosis by obtaining appropriate cultures. Antibiotics should not be given before obtaining appropriate cultures unless there is a life-threatening situation (e.g., septic shock).
Rapid tests, such as antigen tests, are useful for preliminary diagnosis and are included in numerous bacterial, viral, fungal, and parasitic antigen detection tests. Serologic tests, using enzyme-linked immunosorbent assay or Western
CRP, C-reactive protein; ESR, erythrocyte sedimentation rate; IL, interleukin; PAF, platelet-activating factor; TNF, tumor necrosis factor.
*Adenovirus and herpes simplex may cause leukocytosis and increased ESR; Epstein-Barr virus may cause petechiae and increased ESR.
†Early viral (enterovirus, arbovirus) meningitis initially may have a neutrophilic pleocytosis.
‡Nuchal rigidity, bulging fontanelle, Kernig sign, Brudzinski sign.