Sepsis Diagnosis

Sepsis is the body’s hyperactive response to an infection and can lead to inflammation, tissue damage, and severe organ failure. Sepsis is a very dangerous state in which the immune system stops fighting with the invading agents and turns on itself. Around one-third of patients who are affected with sepsis die every year.

Diagnosing sepsis is not an easy task as there is no particular symptom or sign that are directly related to the disease. Doctors doubt sepsis when the patient exhibits more than two infections or related signs. Thus, the diagnosis of sepsis needs a high level of suspicion, through the study of history and physic of the person, appropriate laboratory checkups, and close follow-up of the hemodynamic status of the patient.

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Evaluation of symptoms

Many diseases like pneumonia and diverticulitis that are caused by gram-negative or positive bacteria, viruses or even fungi can be related to sepsis. If the patient shows a number of symptoms and infections, and fall into a risk category, he/she can be doubted for sepsis.

In such cases, the doctor will look for all the signs exhibited by the patient and examine them thoroughly. It is advisable not to wait for the confirmation results to start treatment for sepsis. If the treatment begins at the stage of suspicion itself, the patient has a better chance of recovery.

How is Sepsis Diagnosed?

Evaluation of patient history

Evaluation of patient history, in this case, is done to get information on three things including:

  • Whether the infection that caused sepsis was community-acquired
  • Whether it is nosocomially acquired (acquired from the hospital)
  • If the patient has an impaired immune system

Details of the situation that could have exposed the patient to specific infectious agents are collected. Some important details that can assist in determining a causative agent include whether the patient has a fever, hypotension, or has experienced a loss of consciousness. Noting the patient's alcohol use and normal medication regimen is also important.

Physical examination

If the patient has neutropenic or other pelvic infections, a physical examination that can reveal rectal, perirectal, or perineal abscesses, as well as a pelvic inflammatory disease, abscesses or prostatitis should be performed. The determination of these types of conditions will require rectal, pelvic, and/or genital examinations.

Laboratory tests

For patients suspected of sepsis, a large number of tests are ordered so that the doctor can obtain details on the potentiality and severity of the patient's condition. These tests can also assist in determining the cause of sepsis-like microbial infections or processes.

Some of the different tests that are needed to make a sepsis diagnosis include a urine test, blood test, and tests related to other medical conditions.

Blood tests

For patients with possible signs of sepsis, there are a number of blood tests that can be utilized. Even though these tests cannot diagnose sepsis, combining the results with other information can help.

Some of the different blood tests that can be employed include:

  • Complete blood count (CBC): One of the key takeaways of a CBC test in the context of a sepsis diagnosis is obtaining the white blood cell (WBC) count, as these cells help fight microbes in the blood.
  • Lactate: Lactate levels reflect the presence of lactic acid in the blood, which is an indication of low oxygen.
  • C-reactive protein (CRP) test: C-reactive protein is an indication of inflammation in the body.
  • Blood culture: This test tries to identify the type of bacteria or other microorganisms that serve as the cause for infection.
  • Prothrombin time (PT) and partial thromboplastin time (PTT), platelet count, and d-dimer tests:  Each of these tests is used to assess blood clotting activity in the blood. High PT and PTT indicate poor blood clotting. Low platelet levels indicate unseen clotting in tiny vessels all over the body. An indication of one large clot or many small clotting in the body is identified by the high level of d-dimer.

Confirmatory tests

There are three types of blood tests that can confirm sepsis, which include:

  • Endotoxin test: The identification of endotoxin in the blood confirms the presence of gram-negative bacteria within the blood; however, the specific type of bacteria cannot be identified with this test.
  • Procalcitonin (PCT) test: Low PCT level in the blood means that the disease is not caused by bacteria, but may instead be due to a viral infection or an illness not related to an infection.
  • SeptiCyte test: The products of sepsis-related genes are diagnosed through this test to check if those genes are activated.

Urine test

Two types of urine tests are ordered in cases of sepsis, which include:

  • Urinalysis: This tests for the presence of a urinary tract infection (UTI) or other issues that might exist within the kidneys.
  • Urine culture: A urine culture can be used to determine which bacteria or fungi are causing the UTI.

Tests for related medical conditions

Apart from blood and urine tests, additional tests that are related to other diseases that can cause sepsis are also performed. Some of these can include, but are not limited to:

  • Chest x-ray, pulse oximetry, and sputum test for pneumonia
  • Lumbar puncture, Magnetic resonance imaging (MRI) and Computerized tomography (CT) scan for meningitis
  • Rapid antigen test and the throat culture for strep throat
  • Rapid influenza diagnostic tests and symptom analysis for influenza
  • Skin culturing for infections related to skin


Further Reading

Last Updated: Sep 24, 2022

Afsaneh Khetrapal

Written by

Afsaneh Khetrapal

Afsaneh graduated from Warwick University with a First class honours degree in Biomedical science. During her time here her love for neuroscience and scientific journalism only grew and have now steered her into a career with the journal, Scientific Reports under Springer Nature. Of course, she isn’t always immersed in all things science and literary; her free time involves a lot of oil painting and beach-side walks too.


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