Using Procalcitonin for Sepsis Diagnosis

Instructor: Alexandra Unfried

Alexandra earned her master's degree in nursing education and is currently a hospital supervisor/administrator.

Sepsis is a deadly illness that attacks the body's systems. The earlier sepsis is diagnosed, the better the patient outcome. This lesson will discuss the use of procalcitonin to diagnose sepsis.

Critically Sick

Mike has been feeling under the weather for a couple of days. He is tired and a little achy. However, he is now feeling extremely light- headed and feverish. Mike goes to the emergency room, and the doctor completes an assessment. Mike is showing signs of sepsis, so the doctor wants to order some blood tests that will help make an appropriate diagnosis. Mike asks what sepsis is while the doctor is getting ready to draw his blood.

What is Sepsis?

Sepsis is a systemic infection that is caused by bacteria, fungi, viruses, and parasites. Bacteria are the most common cause of sepsis. The infection causes an inflammatory response in the body that can eventually damage tissues and organs in the body. Common causes of bacterial sepsis come from skin infections, lung infections (pneumonia), gastrointestinal infections (ruptured intestine), surgical site infections, and intravenous catheter infections. Symptoms of sepsis are not all inclusive but consist of:

  • Tachycardia (fast heart rate)
  • Tachypnea (fast breathing rate)
  • Fever (increases temperature)
  • Leukocytosis (elevated white blood cells)
  • Hypotension (decreased blood pressure)
  • Altered mental status (confusion)
  • Chills
  • Dizziness
  • Fatigue
  • Low body temperature
  • Low urine production

Fever is a symptom of sepsis.
Fever is a symptom of sepsis

The three most identified criteria used to definitively diagnose sepsis are tachypnea, hypotension, and altered mental status. The patient has better outcomes and a decreased mortality rate when sepsis is identified early. This is why the doctor wants to act fast and start blood tests to determine the cause of Mike's illness. Mike asks the doctor what specific blood tests are being done.

Blood Tests for Sepsis

Blood cultures are the best way to diagnose sepsis, but they only have a thirty percent diagnosis rate. Blood tests often have a false positive result due to contamination. A definitive diagnosis includes positive blood cultures with the presence of two of the three criteria including low blood pressure, altered mental status, and a fast respiratory rate. Diagnostic tests for sepsis include:

  • Blood cultures
  • White blood cell count
  • Procalcitonin level
  • Partial pressure of carbon dioxide in the blood (PaCo2 done with an arterial blood gas/ABG)
  • Lactate
  • C-reactive protein (CRT)
  • Imaging studies such as X-ray, CT scan, MRI, and ultrasound

Procalcitonin is an important blood test for diagnosing sepsis.
Procalcitonin is an important blood test in diagnosing sepsis

Mike has heard of all of these blood tests before except procalcitonin. He asks the doctor why a procalcitonin level is important.

Procalcitonin use for Sepsis

Procalcitonin is a biomarker that is able to detect early sepsis infections as well as monitor how well antimicrobial treatment is working. It is an inflammatory marker that is released by the body in response to bacterial infection. Procalcitonin has been shown to have a higher success rate of sepsis detection and more specificity than other biomarkers. CRT is another inflammatory marker, but studies have shown that procalcitonin is more accurate.

Mike's blood tests are indicative of sepsis due to an increased procalcitonin level and other blood test results. He had been swimming in a lake with his family last week. Mike cut his foot while swimming, but did not pay much attention to it. Most likely, the cut absorbed some sort of bacteria in the lake, causing sepsis. The doctor wants to admit Mike to the hospital's intensive care unit for further monitoring and treatment. He will need immediate antibiotics and have his vital signs routinely assessed. Mike asks how long he will be hospitalized and what he can expect as far as his treatment is concerned.

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