Bloodstream & Systemic Infections

Causes & Risk Factors

Bloodstream infections can arise from a localized infection that spreads, or occasionally without an obvious initial source:

•  A severe, untreated, or inadequately treated localized infection (such as pneumonia or a urinary tract infection) spreading into the bloodstream.

•  Indwelling medical devices — catheters, central lines — provide a route for bacteria to enter the bloodstream.

•  Recent surgery or invasive medical procedures.

•  Weakened immune system — significantly increases both risk and severity of bloodstream infection.

•  Age extremes — very young infants and older adults are at higher risk of serious bloodstream infection.

Symptoms & When to Test

Bloodstream infection and sepsis can progress rapidly, and recognizing warning signs promptly is critical.

•  High fever or, in some cases (particularly in very young or older patients), abnormally low body temperature

•  Rapid heart rate

•  Rapid breathing or difficulty breathing

•  Confusion or altered mental status

•  Low blood pressure, dizziness, or fainting

•  Extreme weakness or feeling that something is seriously wrong

•  Signs of the underlying source infection, where identifiable

When Should You Consider Testing?

Suspected sepsis or bloodstream infection is a medical emergency requiring immediate evaluation — this is not a situation for routine or delayed outpatient testing. Anyone with fever combined with confusion, rapid heart rate, low blood pressure, or severe unwellness should seek emergency care immediately.

Why Tests Are Combined

Blood culture remains the gold standard for identifying the causative organism in bloodstream infection, but it takes time to yield results — CBC, CRP, and procalcitonin provide much faster information about the presence and severity of infection/inflammation, helping guide immediate treatment decisions while culture results are pending.

Molecular pathogen testing can, in some cases, provide faster organism identification than culture, which is valuable in critically ill patients where treatment cannot wait for culture results, though culture remains important for confirming viability and obtaining full antimicrobial susceptibility information.

Because bloodstream infections and sepsis can progress within hours, this combination of rapid inflammatory markers alongside culture and, where available, molecular testing allows clinicians to begin appropriate treatment promptly while still working toward definitive organism identification.

Tests Available at NPL

Most infectious-disease molecular tests and microbiological investigations do not require fasting. However, some blood tests ordered at the same time may have specific preparation requirements. Please follow the instructions provided by your doctor or NPL.

Home Sample Collection

Suspected bloodstream infection or sepsis is a medical emergency requiring immediate hospital or emergency department evaluation — this is not appropriate for routine home sample collection or outpatient scheduling.

If you or someone with you shows signs of possible sepsis (as described above), seek emergency care immediately rather than arranging a lab test independently.

For patients already under hospital care, NPL supports urgent processing of blood cultures and related tests in coordination with the treating hospital or clinical team.

Less urgent, doctor-directed follow-up testing related to a resolving infection may be arranged through standard channels once the acute situation has been managed by your treating team.

When to See a Doctor

•  Fever combined with confusion, rapid heart rate, or difficulty breathing — seek emergency care immediately

•  Low blood pressure, dizziness, or fainting with signs of infection — seek emergency care immediately

•  Any feeling that an infection is rapidly worsening or that something is seriously wrong — do not wait, seek immediate care

•  Known indwelling catheter or line with new fever — seek prompt evaluation