C-reactive protein

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Community Anatomic Pathology Service (APS)

Test Guide

C-reactive protein

Testing Laboratory

Auckland Te Toka Tumai | Auckland Hospital

Department

Chemical Pathology

Delphic Registration Code (Alpha Code)

CRP

Test Code (Numeric Code)

Laboratory Handling

Sample Stability

Serum 2 weeks at 15-25°C, 3 weeks 2-8°C, 12 months at -20°C, EDTA 1 day at 15-25°C, 3 weeks at 2-8°C, 12 months at -20°C

Synonyms

CRP

Turnaround Time

3 hours

Specimen Type

Plasma
Serum

Specimen Requirements

Tube/Container Type:

Preferred

Lithium Heparin PST- Gel (Light Green Cap)

Acceptable

EDTA (Lavender Cap)
Lithium Heparin PST- Gel (Light Green Cap)
Plain (Red Top)
SST II (Gold Cap)

Preferred Sample Volume (ml)

4.5

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

Heparin (Microtainer)

Acceptable

EDTA (Microtainer)
EDTA (Lavender Cap)
Lithium Heparin - Non-gel (Green Cap)
Lithium Heparin PST- Gel (Light Green Cap)
Plain (Red Top)
SST II (Gold Cap)

Minimum Sample Volume (ml)

0.5

Pre-testing Requirements

Note: Recently changes are implemented to the frequency of retesting CRP, because when monitoring acute phase response, significant change in CRP levels is observed at least after 24 hours:

Any requests for CRP testing in a patient who already has a result reported in the last 20 hours will be automatically declined (allowing a grace period of 4 hours).
In the rare circumstance that more frequent testing is clinically indicated, please contact the laboratory to reinstate.

Additional Specimen Information

4.5 mL PST Blood (Preferred)
Micro-PST 0.5 mL Paediatric Micro-PST Blood (Preferred)
EDTA 5 mL EDTA Blood
Heparin 5 mL Heparin Blood
Plain 4 mL Plain Blood
SST 3.5 mL SST Blood
Microsample 0.5 mL Microsample Serum
Micro-heparin 0.5 mL Paediatric Micro-heparin Blood

Diagnostic Use

CRP is a protein produced by the liver. Its production is regulated by cytokines. The plasma CRP level also is partly genetically determined.

CRP as a marker of inflammation
In unwell patients CRP is useful as a marker of severity of inflammation (for example infections, autoimmune diseases, trauma and malignancies).

In almost all clinical settings it is a more sensitive and specific marker than ESR. It also follows the time course of inflammation more closely, with rise within 4-8 hr of tissue damage and more rapid fall on resolution (half-life about 19 hr). It is also not affected by other factors such as high fibrinogen (pregnancy), haematocrit, or monoclonal bands.

Monitoring of the acute phase response should be done at an interval of at least 24 hours between CRP tests, to observe a significant change in results.

ESR, however, is preferred over CRP in the following conditions:

SLE and variants
Rheumatoid arthritis
Other connective tissue diseases including ankylosing spondylitis, reactive arthritis, Sjogren’s syndrome, systemic sclerosis, antiphospholipid syndrome
Acute rheumatic fever and endocarditis monitoring
Usually only ESR or CRP is required. There is no need to request both. The only known evidence-based exception is for assessment of periprosthetic joint infections of the hip and knee (Guideline published by the American Academy of Orthopaedic Surgeons in 2010, which recommended both ESR and CRP).

CRP as a cardiovascular risk marker
In well patients CRP has some utility as a CVD risk marker. In this context it is called high sensitivity or hsCRP as t he levels measured are usually below 5mg/L.

At LabPlus the CRP assay can measure down to 0.6 mg/L: results lower than this are reported as “less than 0.6 mg/L”.

Recent guideline documents recommend use of hsCRP currently for cardiovascular risk assessment only in patients where it will influence evidence-based treatment decisions , e.g. those who fall near the threshold for drug treatment. Measurement is not recommended for:

– routine CVD risk screening of the general population

– for those already known to be at high risk, or

– for monitoring

As an example, the Canadian guidelines suggest it may be helpful in certain patients at intermediate (10-19% five year) risk, specifically men >50yr and women >60yr with LDL 2mg/L have been shown to benefit from statin therapy (Jupiter trial).

NZGG Guidelines see

http://www.nzgg.org.nz/guidelines/0035/CVD_Risk_Full.pdf keyword “CRP”)

Canadian Guidelines see

http://www.ccs.ca/download/consensus_conference/consensus_conference_archives/2009_Dyslipidemia-Guidelines.pdf )

Reference Intervals

Units: mg/L

Reference ranges:

age < 3 months	0 – 10
age: 3 months to 15 years	0 – 8
adults	0 – 5

Test Method

Principle: Immunoturbidometric assay

Reagents: Roche Tina-quant C-Reactive Protein IV

Analyser: Cobas c702

Limitations / Interference

Drug Interference by carboxypenicillins
Ticarcillin (Claventin) and probably other carboxypenicillins cause negative interference in the CRP assay (Roche) used at Labplus. This may cause falsely low CRP results.

Uncertainty of Measurement

Uncertainty of Measurement : 0.2 mg/L at a concentration of 1.4 mg/L, 7% at concentrations of 4 mg/L and higher.

Last updated: 12/03/2026

Testing Laboratory

Department

Delphic Registration Code (Alpha Code)

Test Code (Numeric Code)

Laboratory Handling

Sample Stability

Synonyms

Turnaround Time

Specimen Type

Specimen Requirements

Tube/Container Type:

Preferred

Acceptable

Preferred Sample Volume (ml)

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

Acceptable

Minimum Sample Volume (ml)

Pre-testing Requirements

Additional Specimen Information

Aliquot Instructions

Sample Type

Diagnostic Use

Reference Intervals

Test Method

Limitations / Interference

Uncertainty of Measurement

Non-Funded Test Cost

Additional Costing Information

Contact Information

Enquiry Form

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C-reactive protein

Overview

Testing Laboratory

Department

Delphic Registration Code (Alpha Code)

Test Code (Numeric Code)

Laboratory Handling

Sample Stability

Synonyms

Turnaround Time

Specimen

Specimen Type

Specimen Requirements

Tube/Container Type:

Preferred

Acceptable

Preferred Sample Volume (ml)

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

Acceptable

Minimum Sample Volume (ml)

Pre-testing Requirements

Additional Specimen Information

Referral

Aliquot Instructions

Sample Type

Clinical Information/Test Method

Diagnostic Use

Reference Intervals

Test Method

Limitations / Interference

Uncertainty of Measurement

Price

Non-Funded Test Cost

Additional Costing Information

Contact Information

Contact Information

Enquiry Form

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