Calculators & Tools

Rule of 7s (Lyme Meningitis)

Distinguishes Lyme meningitis from aseptic meningitis in endemic areas. Low risk only if ALL three are absent.

1 What is the Rule of 7s (Lyme Meningitis)?

The Rule of 7s (Lyme Meningitis) is a infectious scoring tool used in paediatric practice. Distinguishes Lyme meningitis from aseptic meningitis in endemic areas. Low risk only if ALL three are absent. It scores 3 criteria and interprets the total across 2 bands, so the number always arrives with the severity it implies rather than on its own. In PediAid each criterion is shown as a labelled option with the weight it carries, so the total can be checked rather than taken on trust.

2 When to use it

  • Grading severity at the bedside in infectious
  • Recording an objective severity band in the case notes
  • Deciding when a total crosses the threshold for escalation
  • Re-scoring to track whether a child is improving or deteriorating
  • Checking the exact criteria of a score used infrequently

3 Formula & method

The score sums 3 criteria: Headache for ≥ 7 days; CSF mononuclear cells ≥ 70 %; Seventh (or other) cranial-nerve palsy. Totals are then banded: any score - Low risk: none of the three present - low risk for Lyme meningitis (NPV ≈100%). Outpatient management pending serology may be reasonable in endemic areas; 1 risk factor or more - Not low risk: one or more present - not low risk. Send Lyme serology and manage as possible Lyme meningitis pending results.
  • Applies to children in Lyme-endemic regions presenting with CSF pleocytosis. Not applicable in non-endemic settings.
  • Source: Garro AC et al. Prospective validation of a clinical prediction model for Lyme meningitis in children. Pediatrics 2009;123:e829-34.

4 Frequently asked questions

How many criteria does the Rule of 7s (Lyme Meningitis) use?

3. They are Headache for ≥ 7 days; CSF mononuclear cells ≥ 70 %; Seventh (or other) cranial-nerve palsy.

What do the bands of the Rule of 7s (Lyme Meningitis) mean?

The total is interpreted as: any score - Low risk: none of the three present - low risk for Lyme meningitis (NPV ≈100%). Outpatient management pending serology may be reasonable in endemic areas; 1 risk factor or more - Not low risk: one or more present - not low risk. Send Lyme serology and manage as possible Lyme meningitis pending results.

Does the score replace clinical judgement?

No. It is a structured way to record and communicate severity. A clinician concerned about a child should act on that concern regardless of the total.

Where does this score come from?

Applies to children in Lyme-endemic regions presenting with CSF pleocytosis. Not applicable in non-endemic settings.

Does it work offline?

Yes. Score definitions are bundled with the PediAid app, so the score computes without a connection.

For qualified clinicians. This page and the PediAid app are a clinical aid only. Calculations and reference data must be verified against the patient's clinical context, the source guideline and your local protocols before any treatment decision is made.