Investigations
1st investigations to order
blood culture
Test
The most common method of establishing the diagnosis, although sensitivity ranges from 20% to 80%. A positive culture is always significant and is not considered a contaminant. A negative blood culture does not rule out the diagnosis in the appropriate clinical setting.
Large blood volumes and repeated cultures may improve the sensitivity.
With advancements in automated blood culture systems, Candida is typically recovered on routine blood cultures. The role of fungal blood cultures in the diagnosis of candidiasis is unclear and fungal blood cultures seem to be largely unnecessary for most patients. These may be used to supplement routine blood cultures especially if other fungal infection is included in the differential.[45]
Result
positive or negative
FBC
Test
WBC count is sensitive but not specific for the diagnosis of sepsis.
Thrombocytopenia of non-haemorrhagic origin may occur in patients who are severely ill with sepsis.
Result
WBC count 12 x 10⁹/L (>12,000/microlitre) or <4 x 10⁹/L (>4000/microlitre), low platelets
ABG
Test
Should be performed if sepsis is suspected.
Blood gas evaluation facilitates optimisation of oxygenation.
Differentiation of respiratory from metabolic acidosis allows metabolic demands to be identified and treated.
Repeat blood gases are indicated depending on the clinical state of the patient.
Result
hypoxaemia, hypercapnia
lactate levels
Test
Should be performed if sepsis is suspected.
Venous and/or arterial blood may be sampled.
Lactate levels are an index of global inadequate tissue perfusion.
Increasing levels of lactate are associated with increasing levels of anaerobic metabolism.
Persistently elevated lactate levels may parallel the degree of malperfusion or organ failure.
Result
hyperlactataemia: 2-5 mmol/L; shock: ≥4 mmol/L
coagulation studies
Test
Initial test performed in patients with suspected sepsis. Should be done before central line placement.
Result
prolonged INR, PTT, and PT
renal function tests
Test
Should be performed if sepsis is suspected.
Elevated creatinine is a sign of sepsis.
Result
creatinine twice normal
LFT
Test
Should be performed if sepsis is suspected.
Comorbidity of underlying hepatic disease can affect drug metabolism and outcome in sepsis.
Septic shock can compromise hepatic blood flow and metabolism, including lactate.
Result
elevated alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, gamma glutamyl transpeptidase, and bilirubin
serum glucose
Test
Should be performed if sepsis is suspected.
Result
may be elevated, or more rarely, low
Investigations to consider
1,3-beta-D-glucan
Test
US Food and Drug Administration (FDA)-approved as an adjunct for the diagnosis of systemic candidiasis. False-positive results may occur with antibiotics, surgical gauze, haemodialysis, or use of intravenous immunoglobulin. High levels may be more specific (>500 picogram/mL). However, negative predictive value is good.[50][52][58][59]
Result
positive result may indicate systemic infection
matrix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF) mass spectrometry
Test
Cultures from patient samples are ionised and matched to a reference organism database for identification. The US Food and Drug Administration (FDA) has approved use of a MALDI-TOF system to identify Candida to the species level including Candida auris.[46]
Result
identification of Candida species from positive culture
T2 magnetic resonance assay
tissue biopsy
Test
Considered definitive evidence of invasive candidiasis, regardless of source.
Result
yeast forms or pseudohyphae seen in tissue
ultrasound
Test
Often used as the initial imaging modality, especially in the liver and spleen. Ultrasound of the kidneys and urinary system may also be done as well as for other intra-abdominal infections.
Result
fungal balls, abscesses, focal lesions, or abnormalities of the urinary system
CT scan
Test
Imaging modality of choice for lung involvement. May also be used to detect deep-seated infections in the liver, spleen, and kidneys.
Result
may show lung nodules, or identify abscesses or hypodense lesions in different organs
MRI
Test
Beneficial for evaluating central nervous system (CNS) involvement, identifying other soft tissue infections, and characterising intra-abdominal lesions.
Result
CNS: meningitis, cerebritis, ventriculitis, brain abscesses; lesions in bones, soft tissues, spine and intra-abdominal organs
Emerging tests
polymerase chain reaction
Test
Although there have been reports of successful use of polymerase chain reaction and increased sensitivity compared with blood cultures, it is not widely commercially available.[57]
Result
identification of Candida DNA
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