Rate of blood culture contamination in a teaching hospital: a single center study

Objectives: Contamination of blood samples can lead to serious problems in patient management. The administration of unnecessary antibiotics, wastage of hospital resources, and risks to patient life are some of the known hazards. This study aimed to calculate the rate of blood culture contamination and associated factors at King Khalid University Hospital [KKUH], Riyadh, KSA

Methods: This is a retrospective cross-sectional study. The total study population was calculated based on a review of all of the request sheets for blood cultures submitted to the microbiology laboratory from 1st of January to 31st of December, 2012, at KKUH, Riyadh, KSA

Results: The rate of blood culture contamination [false positive] was 1.9%, while 8.71% of the blood culture samples had true infections [true positive]. Coagulase negative staphylococcus [CoNS] was the most predominant isolate [87%]. The rate of blood culture contamination was significantly higher during the summer season of June [1.38%], July [3.97%] and August [3.72%] compared to other months of the year [p value < 0.05]. The surgical units in this study had the highest rate of blood culture contamination [3.92%], followed by intensive care [2.61%] and medical units [2.48%]

Conclusion: The rate of blood culture contamination at KKUH is within the acceptable international range. The highest rates of blood culture contamination occurred during the summer season and in the surgical units

role of rapid testing and clinical decision in the diagnosis of human influenza A H1N1 infection

To evaluate the role of the rapid influenza diagnostic test [RIDT] and clinical decision in the diagnosis of H1N1. In November 2009, 290 suspected influenza patients were examined for H1N1 during an outbreak in Riyadh, Saudi Arabia. Nasopharyngeal swabs were analyzed using Directigen EZ Flu A+B kit. Monoclonal anti-human influenza A/B and reverse transcription- polymerase chain reaction [RT-PCR] were used. Positive and negative controls were used in each run of specimens. Validity indices were calculated for RIDT and clinical diagnostic criteria. The sensitivity and specificity of RIDT were 40.5% [95% confidence interval [CI]: 33.0-48.5], and 94.5% [95% CI: 88.6-97.6]. The sensitivity of clinical decision was 66.3% [95% CI: 58.4-73.4], and the specificity was 65.4% [95% CI: 56.3-73.4]. The sensitivity of clinical decision was higher in early presenters [79.2%; 95% CI: 57.3-92.1]. The RIDT sensitivity was higher in younger patients [48.4%; 95% CI: 35.7-61.3]. The positive predictive value [PPV] was 90.4% [95% CI: 80.7-95.7] for RIDT, and 71.1% [95% CI: 63.1-78.0] for clinical decision. The PPV for RIDT was greater for older [94.7%; 95% CI: 80.9-99.1] and late [90.7%; 95% CI: 76.9-97.0] presenters. The adjusted odds ratio for clinical decision was significant for cough, headache, and fatigue. The RIDT can be useful in epidemics and high prevalence areas, whereas clinical decision, and RT-PCR complement the diagnosis of H1N1 in any setting