Bacterial Meningitis: Likelihood Ratios

Introduction: i.e. acute meningitis

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The likelihood ratios of findings for Bacterial Meningitis are listed below. See the left navigation bar to change the display.

Pre-Test Probability (Prevalence): %.	Post-Test Probability (Predictive Value): %.	Switch to display mode.
Note that calculating probabilities from more than one** finding is inherently inaccurate because findings are not independent. (For example, using two positive findings that share a common pathogenesis is likely to overestimate the true probability.)

Poorly Diagnostic Findings
Finding	Result	+LR	-LR
[ + ] Brudzinski Sign	+ 0 -	1	1
Not well studied. Brudzinski's original study gave sensitivity of 97%. His best known "nape of the neck" sign (Brudzinski sign) is present when passive neck flexion in a supine patient results in flexion of the knees and hips. A separate sign, the contralateral reflex, is present if passive flexion of one hip and knee causes flexion of the contralateral leg. Study: Nakao JH, Jafri FN, Shah K, Newman DH. Jolt accentuation of headache and other clinical signs: poor predictors of meningitis in adults. Am J Emerg Med. 2014 Jan;32(1):24-8.
[ + ] hearing loss	+ 0 -	0.7	1
The maneuver is most commonly performed with the patient lying supine and the hip flexed at 90°. A positive sign is present when extension of the knee from this position elicits resistance or pain in the lower back or posterior thigh.rnrnone study. Brudzinsksi's original study had a sensitivity of 57%. Study: Nakao JH, Jafri FN, Shah K, Newman DH. Jolt accentuation of headache and other clinical signs: poor predictors of meningitis in adults. Am J Emerg Med. 2014 Jan;32(1):24-8.
[ + ] hearing loss		Sensitivity = 85%
specificity not assessed Study: JAMA. 1999 Jul 14;282(2):175-81. PMID: 10411200
[ + ] Neck Stiffness		Sensitivity = 70%
specificity not assessed, however: 13% of the acute-care patients and 35% of the geriatric patients had nuchal rigidity despite the absence of meningitis. Study: JAMA. 1999 Jul 14;282(2):175-81. PMID: 10411200
[ + ] Altered Mental Status		Sensitivity = 67%
specificity not assessed Study: JAMA. 1999 Jul 14;282(2):175-81. PMID: 10411200
[ + ] Headache		Sensitivity = 50%
specificity not assessed. One study gave sensitivity of 15% and specificity of 100%. Study: JAMA. 1999 Jul 14;282(2):175-81. PMID: 10411200
[ + ] Fever, Neck Stiffness, and Altered Mental Status		Sensitivity = 46%
specificity not assessed Study: JAMA. 1999 Jul 14;282(2):175-81. PMID: 10411200
[ + ] Neck Pain		Sensitivity = 28%
specificity not assessed. One study. Study: JAMA. 1999 Jul 14;282(2):175-81. PMID: 10411200
[ + ] Focal Neurological Signs		Sensitivity = 23%
specificity not assessed Study: JAMA. 1999 Jul 14;282(2):175-81. PMID: 10411200
[ + ] Rash		Sensitivity = 22%
specificity not assessed Study: JAMA. 1999 Jul 14;282(2):175-81. PMID: 10411200

Good Positive and Negative Likelihood Ratios
Finding	Result	+LR	-LR
[ + ] CSF Gram Stain	+ 0 -	inf	0.1
older studies gave sensitivity closer to 60%. Study: JAMA. 2006 Oct 25;296(16):2012-22. PMID: 17062865
[ + ] Jolt Accentuation of Headache	+ 0 -	2.4	0.1
Ask the patient to turn his or her head horizontally at a frequency of 2 to 3 rotations per second. Worsening of a baseline headache represents a positive sign. Study: JAMA. 1999 Jul 14;282(2):175-81. PMID: 10411200
[ + ] CSF Lactate	+ 0 -	21	0.1
>=31.5mg/dl Study: JAMA. 2006 Oct 25;296(16):2012-22. PMID: 17062865
[ + ] CSF Leukocytosis	+ 0 -	15	0.3
>=500/ul Study: JAMA. 2006 Oct 25;296(16):2012-22. PMID: 17062865
[ + ] CSF-Blood Glucose Ratio	+ 0 -	18	0.3
<=0.4 Study: JAMA. 2006 Oct 25;296(16):2012-22. PMID: 17062865
[ + ] CSF Glucose	+ 0 -	23	0.5
>39.6mg/dl Study: JAMA. 2006 Oct 25;296(16):2012-22. PMID: 17062865