Innovation for Reducing Blood Culture Contamination: Initial Specimen Diversion Technique

ABSTRACT

We hypothesized that diversion of the first milliliter of venipuncture blood—the initial specimen diversion technique (ISDT)—would eliminate incompletely sterilized fragments of skin from the culture specimen and significantly reduce our blood culture contamination rate (R). We studied our hypothesis prospectively beginning with our control culture (C) definition: one venipuncture with two sequentially obtained specimens, 10 ml each, the first specimen (M1) for aerobic and the second (M2) for anaerobic media. The test ISDT culture (D) was identical, with the exception that each was preceded by diverting a 1-ml sample (D_S) from the same venipuncture. During the first of two sequential 9-month periods, we captured D versus C data (n = 3,733), where D_MX R and C_MX R are R for D and C specimens. Our hypothesis predicted D_S would divert soiled skin fragments from D_M1, and therefore, C_M1 R would be significantly greater than D_M1 R. This was confirmed by C_M1 R (30/1,061 [2.8%]) less D_M1 R (37/2,672 [1.4%]; P = 0.005), which equals 1.4%. For the second 9-month follow-up period, data were compiled for all cultures (n = 4,143), where AD_MX R is R for all (A) diversion specimens, enabling comparison to test ISDT. Our hypothesis predicted no significant differences for test ISDT versus all ISDT. This was confirmed by D_{M 1} R (37/2,672 [1.4%]) versus AD_{M 1} R (42/4,143 [1.0%]; P = 0.17) and D_M2 R (21/2,672 [0.80%]) versus AD_M2 R (39/4,143 [0.94%]; P = 0.50). We conclude that our hypothesis is valid: venipuncture needles soil blood culture specimens with unsterilized skin fragments and increase R, and ISDT significantly reduces R from venipuncture-obtained blood culture specimens.