Rule of 7s for Lyme Meningitis

Why Use

Validated by a retrospective cohort study of over 400 children in Lyme endemic areas. Can help guide clinicians assessing the need to initiate antibiotic therapy for Lyme meningitis (LM), versus observation and close follow-up.

When to Use

In Lyme endemic areas when deciding to start antibiotics in pediatric patients who: Are 2–18 years old, AND Have undergone a lumbar puncture and CSF demonstrates pleocytosis (CSF WBC ≥10 cells/mm³, corrected for CSF RBC if >500 using a ratio of 1 WBC for every 500 RBC).

Formula

Pearls / Pitfalls

If CSF RBC >500, CSF WBC must be corrected using a ratio of 1 WBC for every 500 RBC in the CSF cell count. Should not be used in settings where patients do not have access to close follow-up with a medical provider.

Management

If patient is low risk for LM, consider discharge and discuss with patient and primary care provider to ensure adequate follow-up. If patient is not low risk for LM, consider antibiotic therapy that will cover Borrelia burgdorferi , taking into account the patient’s age.

Critical Actions

The Rule of 7s is meant to aid in the decision to start antibiotics for suspected Lyme versus aseptic meningitis. It should not replace clinical judgement and clinician assessment of patients.

Advice

This tool should be used to assist a clinician in decision-making and not replace clinical evaluation of a patient. Patients with scores 1–3 are NOT low risk for Lyme meningitis, and antibiotic therapy for LM should be considered. Patients with scores 0 are at low risk for LM. Symptoms may be due to aseptic meningitis or other etiology. Use clinical judgment and consider availability of follow-up with both the patient and primary care provider before electing to treat patient symptoms with antibiotics.

More Information

Interpretation: Rule of 7s Risk 0 points Low risk for Lyme meningitis 1–3 points Not low risk for Lyme meningitis