Likelihood Ratios

Appendicitis in a Patient with Right Iliac Fossa Pain Investigations Likelihood Ratios

The tables show the variables with the highest +LR and ROC values from the meta-analysis.

Table 1

Predictive power of clinical and laboratory values in diagnosing appendicitis (likelihood ratios of 2 or more shown in increasing order) [10]
Variable	Positive likelihood ratio	P value
Pain migration	2.06 (1.63, 2.60)	<0.001
CRP raised	2.39 (1.67, 3.41)	0.001
Guarding	2.48 (1.60, 3.84)	0.015
Percussion tenderness	2.86 (1.95, 4.21)	0.820
Rigidity	2.96 (2.43, 3.59)	<0.001
WCC raised	3.47 (1.55, 7.77)	0.008
WCC and CRP raised	23.32 (6.87, 84.79)	None given
Guarding/rebound and WCC raised	11.34 (6.65, 19.56)	None given

Table 2

Discriminatory power of clinical and laboratory values in diagnosing appendicitis (ROC 0.65 or more in increasing order) [10]
Variable	Pooled ROC area	P value
Migration of pain	0.68	<0.001
Guarding	0.68	<0.001
Rebound	0.70	<0.001
Percussion	0.70	0.793
CRP level	0.75	<0.001
WCC	0.77	0.171
Guarding and WCC raised	0.84	None given
WCC and CRP raised	0.96	None given

While each of these variables independently has a fairly weak predictive and discriminatory value, they are of most use in combination, e.g. signs of peritonism and a raised WCC attain high +LRs and ROC values [10].

Learning bite

Migration of pain, RIF rigidity and guarding with raised inflammatory markers in combination strongly suggest appendicitis [10].

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