The Relationship Between Blood Sample Volume and Diagnostic Sensitivity of Blood Culture for Typhoid and Paratyphoid Fever: A Systematic Review and Meta-Analysis.

BACKGROUND

Blood culture is the standard diagnostic method for typhoid and paratyphoid (enteric) fever in surveillance studies and clinical trials, but sensitivity is widely acknowledged to be suboptimal. We conducted a systematic review and meta-analysis to examine sources of heterogeneity across studies and quantified the effect of blood volume.

METHODS

We searched the literature to identify all studies that performed blood culture alongside bone marrow culture (a gold standard) to detect cases of enteric fever. We performed a meta-regression analysis to quantify the relationship between blood sample volume and diagnostic sensitivity. Furthermore, we evaluated the impact of patient age, antimicrobial use, and symptom duration on sensitivity.

RESULTS

We estimated blood culture diagnostic sensitivity was 0.59 (95% confidence interval [CI], 0.54-0.64) with significant between-study heterogeneity (I2, 76% [95% CI, 68%-82%]; P < .01). Sensitivity ranged from 0.51 (95% CI, 0.44-0.57) for a 2-mL blood specimen to 0.65 (95% CI, 0.58-0.70) for a 10-mL blood specimen, indicative of a relationship between specimen volume and sensitivity. Subgroup analysis showed significant heterogeneity by patient age and a weak trend towards higher sensitivity among more recent studies. Sensitivity was 34% lower (95% CI, 4%-54%) among patients with prior antimicrobial use and 31% lower after the first week of symptoms (95% CI, 19%-41%). There was no evidence of confounding by patient age, antimicrobial use, symptom duration, or study date on the relationship between specimen volume and sensitivity.

CONCLUSIONS

The relationship between the blood sample volume and culture sensitivity should be accounted for in incidence and next-generation diagnostic studies.