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Orthopaedic Surgery

General Information

MRSA PCR: Updated indications for ordering

Effective Date: September 3, 2025

The MRSA Screen PCR [LAB1231076] detects the presence or absence of colonization with methicillin-resistant Staphylococcus aureus (MRSA) and may be used to guide antimicrobial prophylaxis decisions. To improve and standardize test utilization across all Corewell Health regions, the following restrictions will be added to this test order:

  • Ordering will be restricted to one test every 7 days.
  • An indication for ordering must be provided for each order. Acceptable indications are:
    • Pneumonia
    • Skin and soft tissue (use for non-purulent infections)
    • Surgical prophylaxis

Studies have shown that there is minimal utility in re-testing within 2 weeks as MRSA conversion rates are low and the PCR negative predictive values remain high for at least 14 days after initial testing.

Absence of nasal colonization with MRSA cannot be used to reliably rule out MRSA infection in scenarios other than those listed above.

Test Information

MRSA Screen PCR [LAB1231076]

Microbiology

Sinus Culture Order Considerations

The management of sinusitis is often aided by bacterial and fungal cultures from which Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus, and occasionally aerobic Gram-negative bacilli are the most commonly recovered pathogenic organisms. The Corewell Health West Microbiology Lab has several orders available for culturing sinus specimens collected as fluid aspirates, tissue, or swabs. Though more challenging to collect, aspirates are preferred over swab cultures that often grow mixed normal upper respiratory flora for which it is difficult to interpret the clinical significance.

Available Sinus Culture Orders Default Specimen Type Comments
Body Fluid Culture [LAB2111016]

Respiratory Culture [LAB3095]

Tissue Culture [LAB2111173]

Aspirated fluid

Swabbed collection

Tissue

For aerobic bacteria
Fungal Culture [LAB240] Aspirated fluid or tissue, preferred

Swabbed collection

For fungal organisms
Anaerobic Culture [LAB233] Aspirated fluid or tissue* For anaerobic bacteria

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Hematology

Result Reporting Change of Nucleated Cells in Cerebrospinal Fluid (CSF) Counts

Cell Count w/ Differential if indicated, Cerebrospinal Fluid [LAB2111025] and Cell Count with Differential, Cerebrospinal Fluid (Pediatric Oncology) [LAB212] currently result nucleated cell counts as a White Blood Cell (WBC) count.

Effective Tuesday, August 16, 2022, the WBC component will be removed and instead reported as a Total Nucleated Cell (TNC) Count for CSF.

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