Continuous quality improvement for introduction of automated blood culture instrument

Abstract

Despite the critical nature and high cost of blood cultures, hospitals rely on manufacturers' test site data. As a result, in-hospital testing and compliance evaluation of newly acquired instruments are seldom done. The goal of this study was to apply a continuous quality improvement approach and to develop assessment criteria for all stages from the purchase order, through the on-site instrument evaluation, to the compliance evaluation. Despite the introduction of an automated high-blood-volume instrument (BacT/Alert) in our hospital, 56% of adult patients had only one venipuncture and 89.5% had Յ20 ml of total blood volume sampled. False positives were associated with overfilling of bottles. These problems occurred because the phlebotomists did not like to perform multiple venipunctures on ill patients; therefore, they were drawing 20 ml of blood from one venipuncture and splitting it between two bottles. Unknown to the staff, the vacuum in the bottles draws significantly more than 10 ml of blood; therefore, the first bottle in the set was frequently overfilled and the second bottle was frequently underfilled. A diagrammatic guideline for a new blood culture protocol based on two venipunctures, taken one immediately after the other, to inoculate three bottles was developed. Compliance evaluation demonstrated that within 1 month of starting the new protocol, 74% of patients had at least two or more venipunctures and 60% had Ն30 ml of blood drawn per patient episode. This study demonstrates the need for continuous quality improvement, including compliance evaluation, to ensure that the potential benefits of newer blood culture technology are actually realized.

Evaluation of the VITAL (bioMérieux) automated blood culture system using blind subculture

“…This creates an extra workload for laboratory technical staff. Although automated systems have not eliminated this problem completely, they have decreased the false‐positive rate, which should always be equal to or lower than 2% [5]. During our evaluation of the VITAL system, this rate was 3.2%, higher than for the semiautomatic Bactec NR 660, which was introduced to the market in 1972 [21].…”

“…Another possible explanation of the high number of false‐positive results in the anaerobic bottle could be the tendency to inoculate an excess of blood (more than 10 mL), favored by the negative pressure in the bottle. The leukocytes in this high blood volume would produce enough CO 2 to cause the system to indicate the bottle as positive [5].…”

“…The false‐negative rate of the evaluated system was 0.6%, slightly higher than considered acceptable (≤0.5%) [5] and with a large number of clinically significant isolations (73%), compared to 25% [5], which is the maximum tolerable. Among Gram‐positive cocci, MARSA was recovered twice from blind subculture, implying system limitations for growth detection of this microorganism.…”

“…The results obtained were evaluated according to common standards [5], considering as adequate a positive blood cultures rate ≥8%, a false‐negative rate ≤0.5%, a false‐positive rate ≤2% and a contamination rate ≤3%.…”

Update on detection of bacteremia and fungemia.

“…Collection procedure. Every clinical microbiology laboratory needs policies and procedures designed to ensure that blood cultures are collected in a timely manner, in such a way as to minimize contamination, and that proper blood volumes are inoculated into the bottles (1,14,110). Whenever possible, blood should be collected by venipuncture of peripheral veins and not via indwelling vascular catheters (26).…”