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What Is A PCT Test: Antibiotic Stewardship Goals

Updated on August 14, 2017

Sepsis

The Greek word "sepo" means "I rot". The first mention of the word sepsis occurs in the poems of Homer.Although the mortality in sepsis has reduced from 50%-75% to a range of 30%-50% the incidence of sepsis has increased annually in the past forty years.This reduction in mortality is largely attributable to the discovery and use of antibiotics in the past hundred years of medicine.The total deaths sepsis causes is statistically similar to myocardial infarction.

Sepsis Epidemiology

USA

Population: 2.4 to 3% incidence in general population.

ICU: 10-14% incidence in ICU patients.

India

ICU: 16% incidence in general population.

Brun-Buisson et al. JAMA 1995

S Todi et al. Crit Care 2007

Sands et al. JAMA 1997

Systemic Inflammatory Response Syndrome (SIRS):Not The Same As Sepsis

Systemic inflammatory response syndrome (SIRS) may occur in the absence of infection.

Two or more of the SIRS criteria are needed to document it-

  • Temperature more than 380C (100.40F) or less than 360C (96.80F)
  • Heart rate more than 90 beats/minute
  • Respiratory rate more than 20 /min or PaCO2 < 32 mmHg
  • White Blood Cell Count(WBC ) more than 12,000 cells/mm3, or 4,000 cells/mm3, or more than 10% immature (band) form of white blood cells.

So What Is Sepsis?

Sepsis –

Systemic response to infection – It is confirmed or suspected infection plus 2 SIRS criteria.

Severe Sepsis –

Sepsis associated with organ dysfunction, hypo perfusion, or hypo tension

Septic Shock –

Severe Sepsis that cannot be resuscitated or stabilized with IV fluids alone.

Adapted from SCCM ACCP Consensus Guidelines BSI= Blood Stream Infections
Adapted from SCCM ACCP Consensus Guidelines BSI= Blood Stream Infections

Clinicians Dilemma

So if you have fever, a fast heart rate, fast breathing and increased white blood cells you do not necessarily have sepsis because these can occur in the presence of systemic inflammatory response syndrome.For sepsis the presence of infection (either suspected or confirmed by microbial techniques) is necessary.So medical conditions like pancreatitis, burns, trauma may present with fever , tachycardia, tachypnea and increased white cell count either due to SIRS or Sepsis and there is no objective way to differentiate one from another.

What Is An Ideal Bio Marker?

A bio marker may be simply defined as a laboratory measurement that reflects the activity of a disease process.An ideal bio marker should not only help in the early diagnosis of a disease but also provide information regarding its severity and prognosis.Serial measurements of an ideal bio marker before and after the therapy should show decline to indicate the effectiveness of therapy.Erythrocyte Sedimentation Rate(ESR) is the oldest bio marker and is in use from the past ninety years.Other common bio marker is C reactive protein (CRP) which in use since the past 30 years.

Rangel et al. JAMA 1995
Rangel et al. JAMA 1995

Mortality In Sepsis

Seligman R et al.Crit. Care 2006 SS= Septic Shock
Seligman R et al.Crit. Care 2006 SS= Septic Shock

Why Do We Need A Bio Marker Like Procalcitonin?

A bio marker like procalcitonin may help differentiate SIRS from sepsis.This differentiation is of paramount importance because infection or sepsis would require antibiotics whereas inflammatory conditions do not require antibiotic treatment.A misdiagnosis may result in either cost escalation of treatment if antibiotics are administered to a person not suffering from sepsis whereas if antibiotics are delayed or denied in a patient of sepsis it will cause increased mortality or morbidity.So the best case scenario will be a bio marker which will objectively differentiate a infective cause of illness from a not infective one to guide the clinical decisions regarding antibiotic administration, thereby taking the guesswork out of the equation.

Procalcitonin Biochemistry

        Morgenthaler N. et al., Clin Lab 2002
Morgenthaler N. et al., Clin Lab 2002

Procalcitonin (PCT) : A Prohormone

It is a protein composed of a chain of 116 aminoacids.It is a pro-hormone of calcitonin and is secreted from all parenchymal tissues in response to bacterial infection. Calcitonin on the other hand is secreted by the C cells of the thyroid only.The regulation of procalcitonin is by the CALC-1 gene located on chromosome 11.A bacterial infection increases the CALC-1 gene expression and stimulates the release of procalcitonin. The normal serum procalcitonin level is less than 0.05 ng/ml.

Brunkhorst FM et al., Intens Care Med 1998
Brunkhorst FM et al., Intens Care Med 1998

Procalcitonin Kinetics in Sepsis

Procalcitonin levels start increasing within three hours of infection and levels peak in blood at six to twelve hours after infection.It has a half life of around twenty four hours after which levels start declining.

Role of Procalcitonin In Clinical Practice

Assist in the diagnosis of sepsis

To monitor clinical course & therapy

Predict prognosis of disease

Limitations of Procalcitonin As Biomarker

PCT may increase without sepsis
PCT may be normal in sepsis
New born less than 48 hours of birth
Bacterial Infection (If localized)
Trauma
Early phase of sepsis
Burns
Viral Infections
Surgery
Fungal Infections
Medullary C-cell cancers of the thyroid
Parasitic Infections
Bronchial Carcinoma
 
Pulmonary Small-Cell Carcinoma
 

Advantages over C Reactive Protein

 
PCT
CRP
Secretion begins after infection
3 hours
8 hours
Response to treatment
Rapid fall
Protracted response
Effect of steroid & Non steriodal anti inflammatory drugs (NSAID’s)
None
Blunted response

To monitor clinical course & therapy

Significant reduction in antibiotic use

 number of prescriptions and

 duration of use

No impact on mortality, length of hospital stay

Arch Intern Med (2011); Clin Infect Dis (2011); Crit Care Med (2010); Infection (2009)

Systematic review and meta-analysis of procalcitonin guided antibiotic therapy

Good Antibiotic Stewardship

So procalcitonin may be used to assist in the more judicious use of antibiotics both inside and outside Intensive Care Units.A good antibiotic stewardship will prevent the emergence of multi drug resistance bacteria and help reduce the burden of sepsis.

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