#324 Is booking an urgent UTI appointment the best sign of a UTI?

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- Prevalence of UTI: In primary care, 49%-79% women presenting with possible UTI have a UTI depending on criteria for positive culture.1 Others found average prevalence of 55%, 59%, 40-60%.2-4
- UTI symptoms: 4 systematic reviews1,3-5 (4-16 studies, 948-3711 women) in family practice or emergency departments. The largest1 in primary care pooled data with 16 studies and 3711 patients:
- Frequency: Positive likelihood ratio (LR+)=1.09 and Negative Likelihood Ratio (LR-)=0.58
- Dysuria and urgency similar: LR+= 1.17-1.22, LR-= 0.61-0.7
- Others found similar3-5 with highest LR+=2.3 for any symptom.4
- Therefore, clinician elicited symptoms are not very helpful.
- Urine dip (urinalysis): 6 systematic reviews2-4,6-8 (4-43 studies, 948-12,554 women). The largest pooling primary care data3 (11 studies, 2813 patients):
- Leukocytes (≥1+):3 LR+=1.4 and LR-=0.44
- Others2,4,6,7 found LR- similar but LR+=1.0-4.9.
- Overall, leukocytes not very helpful.
- Nitrite (≥1+):3 LR+=6.5 and LR-=0.58
- Others2,4,6,7 found LR- similar and LR+=1.5-29 (highly inconsistent).
- Overall, nitrites are helpful ‘ruling-in’ when positive; not helpful “ruling-out” if negative.
- Blood (≥1+):4 LR+=2.1 and LR-=0.3
- Leukocytes (≥1+):3 LR+=1.4 and LR-=0.44
- Many limitations, examples include no pooling,4,6 differing (102-108) colony forming units as culture gold standard,2,6,7 older than 30 years,8 and differing populations/asymptomatic patients.7
- Urine culture is an imperfect ‘gold’ standard (likely misses cases). Examples:
- Of 220 symptomatic women, 80% had a positive culture but 96% were coli positive on Polymerase Chain Reaction (PCR).9
- Of 42 untreated symptomatic women with initially negative cultures, 31% had a positive culture within 6 weeks.10
- Likelihood ratios provide more information than sensitivity/specificity.
- LR+ for making diagnosis: ≥10 very helpful, 5-9.9 good, 2-4.9 moderate help and <2 provides little help.
- LR- for ruling-out diagnosis: ≤0.1 very helpful, 0.11-0.2 good, 0.21-0.5 moderate help and >0.5 provides little help.