【bio-news】通用引物PCR诊断新生儿败血病
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Universal Primer PCR Test May Aid in Diagnosis of Neonatal Sepsis
http://www.medscape.com/viewarticle/586272
Laurie Barclay, MD
January 5, 2009 — Universal primer polymerase chain reaction (PCR) is accurate in diagnosing neonatal sepsis before antibiotic therapy begins but not once these drugs are given, according to the results of a prospective study reported in the January issue of the Archives of Pediatric and Adolescent Medicine.
"The ideal test for the diagnosis of neonatal sepsis continues to be elusive," write Sourabh Dutta, MD, PhD, from the Postgraduate Institute of Medical Education and Research in Chandigarh, India, and colleagues. "Although blood culture is the currently accepted criterion standard, it may take 48 hours to get a report, and previous antibiotic drug exposure often interferes with growth on blood culture. [PCR] using universal bacterial primers targets conserved regions of the 16S rRNA gene that are common to all bacteria but not found in other organisms."
The goal of this study was to evaluate the ability of universal primer 16S rRNA gene PCR to diagnose blood culture–positive neonatal sepsis before and after starting antibiotic treatment.
At a level 3 neonatal intensive care unit, neonates with a new episode of clinically suspected sepsis were enrolled in this study (242 of 306 patients who were evaluated were included). Exclusion criteria were major malformations, life expectancy less than 12 hours, or contaminated blood cultures. Baseline assessments included blood culture and sepsis screening (complete blood cell counts, microerythrocyte sedimentation rate, and C-reactive protein). PCR was performed before starting antibiotic drug therapy and at 12, 24, and 48 hours thereafter.
The main study endpoints were the sensitivity and specificity of PCR before starting antibiotic therapy (0-hour) for diagnosing blood culture–positive sepsis. The secondary endpoint was the proportion of patients with positive PCR at 0 hours who continued to have positive PCR after starting treatment with antibiotics.
Mean gestation was 32.2 ± 3.1 weeks, and mean birth weight was 1529.2 ± 597.2 g. Of the 242 patients studied, 52 had positive blood culture and 57 had positive 0-hour PCR. For 0-hour PCR, sensitivity was 96.2%, specificity 96.3%, positive predictive value 87.7%, negative predictive value 98.8%, positive likelihood ratio 26.1, and negative likelihood ratio 0.04.
Two patients had positive blood culture but negative 0-hour PCR, whereas 7 patients had positive 0-hour PCR but negative blood culture. Of those patients who had positive 0-hour PCR, 7 were still positive 12 hours after starting antibiotic drug therapy, but none were still positive at 24 and 48 hours after starting antibiotic drug therapy. No predictors of positive 12-hour PCR were identified in patients who had positive 0-hour PCR.
"Universal primer PCR can accurately diagnose neonatal sepsis before but not after antibiotic drugs are given," the study authors write.
Limitations of this study include the possibility of contamination of PCR; difficulty in distinguishing respiratory distress syndrome, apnea of prematurity, and feed intolerance resulting from prematurity from true sepsis; PCR test not repeated at more frequent intervals; and absence of further molecular analysis with gram-specific or organism-specific probes.
"We conclude that the universal bacterial primer PCR is a useful test for diagnosing a fresh case of culture-proven sepsis but that it should not be used for diagnosis if the patient has been exposed to 12 hours or more of antibiotic drug therapy," the study authors conclude. "It is not possible for us to comment on its utility at less than 12 hours after starting antibiotic drug therapy. In the present setting, the 0-hour PCR seems to perform well in patients with suspected [early-onset sepsis], irrespective of antibiotic drug use in the mother; however, this finding may not be applicable to other settings. Larger studies are required before the test can be recommended for routine clinical use."
The authors have disclosed no relevant financial relationships.
Arch Pediatr Adolesc Med. 2009;163:6–11.
http://www.medscape.com/viewarticle/586272
Laurie Barclay, MD
January 5, 2009 — Universal primer polymerase chain reaction (PCR) is accurate in diagnosing neonatal sepsis before antibiotic therapy begins but not once these drugs are given, according to the results of a prospective study reported in the January issue of the Archives of Pediatric and Adolescent Medicine.
"The ideal test for the diagnosis of neonatal sepsis continues to be elusive," write Sourabh Dutta, MD, PhD, from the Postgraduate Institute of Medical Education and Research in Chandigarh, India, and colleagues. "Although blood culture is the currently accepted criterion standard, it may take 48 hours to get a report, and previous antibiotic drug exposure often interferes with growth on blood culture. [PCR] using universal bacterial primers targets conserved regions of the 16S rRNA gene that are common to all bacteria but not found in other organisms."
The goal of this study was to evaluate the ability of universal primer 16S rRNA gene PCR to diagnose blood culture–positive neonatal sepsis before and after starting antibiotic treatment.
At a level 3 neonatal intensive care unit, neonates with a new episode of clinically suspected sepsis were enrolled in this study (242 of 306 patients who were evaluated were included). Exclusion criteria were major malformations, life expectancy less than 12 hours, or contaminated blood cultures. Baseline assessments included blood culture and sepsis screening (complete blood cell counts, microerythrocyte sedimentation rate, and C-reactive protein). PCR was performed before starting antibiotic drug therapy and at 12, 24, and 48 hours thereafter.
The main study endpoints were the sensitivity and specificity of PCR before starting antibiotic therapy (0-hour) for diagnosing blood culture–positive sepsis. The secondary endpoint was the proportion of patients with positive PCR at 0 hours who continued to have positive PCR after starting treatment with antibiotics.
Mean gestation was 32.2 ± 3.1 weeks, and mean birth weight was 1529.2 ± 597.2 g. Of the 242 patients studied, 52 had positive blood culture and 57 had positive 0-hour PCR. For 0-hour PCR, sensitivity was 96.2%, specificity 96.3%, positive predictive value 87.7%, negative predictive value 98.8%, positive likelihood ratio 26.1, and negative likelihood ratio 0.04.
Two patients had positive blood culture but negative 0-hour PCR, whereas 7 patients had positive 0-hour PCR but negative blood culture. Of those patients who had positive 0-hour PCR, 7 were still positive 12 hours after starting antibiotic drug therapy, but none were still positive at 24 and 48 hours after starting antibiotic drug therapy. No predictors of positive 12-hour PCR were identified in patients who had positive 0-hour PCR.
"Universal primer PCR can accurately diagnose neonatal sepsis before but not after antibiotic drugs are given," the study authors write.
Limitations of this study include the possibility of contamination of PCR; difficulty in distinguishing respiratory distress syndrome, apnea of prematurity, and feed intolerance resulting from prematurity from true sepsis; PCR test not repeated at more frequent intervals; and absence of further molecular analysis with gram-specific or organism-specific probes.
"We conclude that the universal bacterial primer PCR is a useful test for diagnosing a fresh case of culture-proven sepsis but that it should not be used for diagnosis if the patient has been exposed to 12 hours or more of antibiotic drug therapy," the study authors conclude. "It is not possible for us to comment on its utility at less than 12 hours after starting antibiotic drug therapy. In the present setting, the 0-hour PCR seems to perform well in patients with suspected [early-onset sepsis], irrespective of antibiotic drug use in the mother; however, this finding may not be applicable to other settings. Larger studies are required before the test can be recommended for routine clinical use."
The authors have disclosed no relevant financial relationships.
Arch Pediatr Adolesc Med. 2009;163:6–11.
