Central venous blood culture: a useful test for catheter colonisation?
OBJECTIVE
To evaluate the widespread practice of using qualitative culture of venous blood taken through central venous catheters (CVCs) as a means of diagnosing catheter colonisation in situ.


METHODS
A prospective clinical study.


METHODS
Three hundred fifty-one CVCs were inserted into 228 critically ill patients.


METHODS
Prior to CVC removal, blood was taken for qualitative culture from the CVC and a peripheral site. All catheter tips underwent semi-quantitative analysis of bacterial colony count [1].


RESULTS
One hundred eighteen (33.6%) CVCs were found to be colonised on removal. A positive central blood culture had a sensitivity and specificity of 50.8% and 78.9% when compared with the 'gold standard' of catheter tip culture. This gives a positive predictive value of 47.7% and a negative predictive value of 76.5%. The sensitivity and specificity of a positive peripheral blood culture were 41.5% and 77.7% with positive and negative predictive values of 48.8% and 72.9%, respectively. When only those catheters removed because of systemic sepsis (n = 139) were considered, a positive central blood culture had a sensitivity of 58.8% and a specificity of 69.3%.


CONCLUSIONS
Our results indicate that the use of central blood culture confers a small advantage in sensitivity compared with peripheral blood culture. This advantage was further improved by only considering the catheters removed because of systemic sepsis but at the cost of a loss of specificity. Qualitative blood culture is a poor tool for the diagnosis of in-situ CVC colonisation.
Juste
R N
RN
Magill Department of Anaesthesia, Chelsea and Westminster Hospital, London, UK. mjuste@hotmail.com
Hannan
M
M
Glendenning
A
A
Azadian
B
B
Soni
N
N
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016470:Bacteremia / Q000175:diagnosis* / Q000209:etiology; D001431:Bacteriological Techniques; D001800:Blood Specimen Collection / Q000379:methods; D002405:Catheterization, Central Venous / Q000009:adverse effects*; D002408:Catheters, Indwelling / Q000382:microbiology*; D015169:Colony Count, Microbial; D004866:Equipment Contamination; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012680:Sensitivity and Specificity