血前降钙素在小儿重症感染诊断中的作用

目的评价血清前降钙素在重症感染诊断中的作用。方法应用免疫荧光法对30例重症感染患儿于入院时和入院后48h进行血清前降钙素水平测定，并比较血清CRP、白细胞计数对感染疾病的实验室诊断价值。结果17例细菌感染患儿血清前降钙素水平明显升高，13例病毒感染患儿血前降钙素水平正常或仅有轻度升高。血清CRP在两组间有数据重叠。经有效抗生素治疗后，血清前降钙素水平的下降幅度明显大于血清的下降幅度(P分别为0．028和0．196)。结论血前降钙素是鉴定细菌感染和病毒感染的重要指标，是判断细菌感染治疗效果的客观依据之一。     

前降钙素和C反应蛋白对儿科细菌感染的诊断价值

目的 评价前降钙素（PCT）、C反应蛋白（CRP）对儿童细菌感染的诊断价值。方法 检测51例患儿（21例细菌感染、17例病毒感染、13例非感染）入院时的血清PCT和外周血CRP水平，并比较他们对细菌感染的敏感度和特异性。结果 细菌感染患儿血清PCT阳性率高于病毒感染和非感染患儿。血清PCT对细菌感染的特异性优于外周血CRP，但敏感性低于CRP。结论 联合应用血清PCT和外周血CRP可提高诊断细菌感染的敏感性和特异性，对临床诊治细菌感染有一定的指导作用。     

血清降钙素原、前清蛋白和C-反应蛋白测定在感染性疾病中的临床意义

目的 探讨感染性疾病患儿血清降钙素原(PCT)、前清蛋白(PA)和CRP测定的临床意义.方法 感染儿童78例被分为细菌感染组(35例)与病毒感染组(43例).2组患儿均检测血清PCT、CRP和PA水平,并与35例年龄、性别相匹配的健康儿童各检测值进行比较.结果 1.以血清PCT≥0.5μg/L为阳性标准,细菌感染组PCT阳性率为80%(28/35例),病毒感染组为18.6%(8/43例);以血清CRP≥8 mg/L为阳性标准,细菌感染组CRP阳性率为68.6%(24/35例),病毒感染组为23.2%(10/43例).2.与健康对照组比较,细菌感染组PCT、CRP均明显升高(Pa<0.01),PA明显降低(P<0.01);细菌感染组PCT、CRP均高于病毒感染组(Pa <0.05),PA明显低于病毒感染组(P<0.01).结论 PCT、PA和CRP的检测对于细菌性感染和病毒性感染的鉴别诊断有一定价值.     

血清前降钙素在新生儿重症感染中的诊断价值

目的 探讨血清前降钙素(PCT)在新生儿重症感染中的诊断价值.方法 应用免疫荧光法对115例重症感染新生儿(细菌感染组75例,病毒感染组40例)和30例无感染征象患儿(对照组)入院时进行血清PCT测定,采用免疫散射比浊法检测CRP和WBC计数,检测结果 分为PCT<0.5 μg/L.0.5～2.0μg/L,2.0～10.0μg/L,≥10.0μg/L 4个等级,PCT0.5μg/L为阳性,2.0 μg/L,为强阳性.对明确细菌感染的新生儿复查PCT及CRP水平.结果 细菌感染组PCT阳性率为96%(72/75例).病毒感染组PCT.阳性率为35%(14/40)例),对照组PCT阳性率为6.67%(2/30例).3组间PCT阳性率两两比较,差异有显著意义(P<0.01).细菌感染组PCT强阳性率为44%(33/75例),与病毒感染组(10%)和对照组(0)比较,差异均有显著意义(Pa<0.01);病毒感染组PCT强阳性率与对照组比较,差异无显著意义(P>0.05).细菌感染组CRP阳性率明显高于病毒感染组和对照组(Pa<0.05);病毒感染组与对照组CRP比较,差异无显著意义(P>0.05).细菌感染组治疗后5例PCT≥10.0μg/L,2例死亡,3例病情恶化自动出院.结论 血清PCT是鉴别细菌感染和病毒感染、细菌感染预后判断及治疗监测的主要指标之一.     

MxA蛋白在病毒、细菌感染鉴别中的应用

目的：探讨血MxA蛋白鉴别病毒与细菌感染诊断指标的应用价值。方法：采用流式细胞仪检测64例患儿血淋巴细胞中MxA蛋白和血清C－反应蛋白（CRP）。结果：病毒感染组血MxA蛋白与对照组相比显著升高（P＜0．01），细胞感染组与对照组相比无显著差异；细菌感染组和腺病毒组血清CRP显著高于对照组（P＜0．01），其它病毒感染组CRP未见升高。结论：作为病毒与细菌感染鉴别诊断指标，MxA蛋白较CRP更具有意义。     

血清降钙素原在儿童重症监护病房的临床应用

目的 探讨血清降钙素原(procalcitonin,PCT)检测在儿童重症监护病房的应用价值.方法 将119例危重患儿分为3组:细菌感染组45例,病毒感染组38例,非感染组36例,回顾分析患儿血清PCT水平,比较PCT检测阴性的非细菌感染危重患儿不用抗生素治疗与经验性使用抗生素的疗效差异.结果 细菌感染组、病毒感染组和非感染组PCT阳性率分别为73.3％,13.2％和13.9％,细菌感染组与病毒感染组、非感染组差异有统计学意义(P＜0.01),PCT检测阴性的非细菌感染危重患儿不用抗生素治疗与经验性使用抗生素的疗效差异无统计学意义(P＞0.05).结论 在儿童重症监护病房血清PCT可用作细菌感染与病毒等感染的鉴别诊断指标,指导临床抗生素的合理使用,降低抗生素使用率,减少耐药菌的产生.     

C反应蛋白、免疫球蛋白和白细胞检测在急性呼吸道感染诊断中的价值

目的　对急性呼吸道感染患儿行C反应蛋白 (CRP)、白细胞及免疫球蛋白 (Ig)检测 ,旨在探讨其对急性呼吸道感染预防及鉴别诊断的价值。方法　白细胞用KS - 2 1血液分析仪测定 ,CRP和Ig采用速率散射比浊法 ,检测 137例呼吸道感染急性期血常规、CRP和Ig。结果　细菌感染组治疗前后CRP比较 ,差异具有极显著意义。呼吸道细菌感染组CRP与白细胞阳性率比较差异有统计学意义 (χ2 =14 .7　P均 <0 .0 0 5 )。细菌和病毒感染组Ig均明显下降。 结论　急性呼吸道感染患儿急性期CRP明显升高 ,可用于鉴别细菌和病毒感染。增强患儿免疫功能 ,是治疗和预防疾病的有效途径之一。     

中性粒细胞CD64在儿童社区获得性肺炎诊断中的价值

目的：探讨外周血中性粒细胞CD64的表达在儿童社区获得性肺炎（CAP）诊断中的价值。方法：依据病原体不同将98例社区获得性肺炎患儿分为细菌感染组（48例）、病毒感染组（29例）以及支原体感染组（21例）;另设健康对照组（20例）。细菌感染组依据患儿的入院情况分为轻症感染组（36例）和重症感染组（12例）。采用流式细胞术检测外周血中性粒细胞CD64的表达,同时免疫比浊法检测外周血C反应蛋白（CRP）的水平。结果：治疗前细菌感染组CD64指数和CRP水平显著高于其他3组,差异有统计学意义（P<0.05）。重症组CD64指数和CRP水平较轻症组显著增高,差异有统计学意义（P<0.05）。细菌感染组经过有效的抗菌治疗后,CD64表达水平下降,和治疗前相比差异有统计学意义（P<0.05）。相关分析结果显示CD64指数与CRP呈正相关（r=0.545,P＜0.01）。 ROC曲线分析结果显示CD64、CRP最佳临界值分别为2.8和8 mg/L,CD64指数的特异性（90%）远高于CRP（74%）。结论：外周血中性粒细胞CD64测定有助于肺部细菌感染的早期诊断,并可以判断病情的严重程度及疗效。     

血前降钙素在儿童细菌性脑膜炎诊断中的应用价值探讨

目的　证实血前降钙素在小儿急性细菌性脑膜炎及病毒性脑炎鉴别诊断中的作用。方法　应用双位点夹心化学免疫荧光法对 6 7例中枢神经系统感染患儿的血浆前降钙素水平进行测定 ,并比较血清C反应蛋白 ,脑脊液白细胞数、蛋白含量对感染病因辅助诊断的价值。结果　 4 5例急性细菌性脑膜炎患儿血浆前降钙素水平明显升高 (4 6 4～ 74 5 0 μg/L) ,2 2例病毒性脑炎的血前降钙素水平仅有轻度升高 (0 10～ 1 2 2 μg/L) ,P <0 0 0 0 1。而血清C反应蛋白 ,脑脊液白细胞数及蛋白含量在急性细菌性脑膜炎及病毒性脑炎中有重叠。结论　血前降钙素是鉴别儿童急性细菌性脑膜炎及病毒性脑炎的有效指标     

新生儿细菌感染时血清IL-8和IL-13水平变化

目的探讨血清IL-8和IL-13水平在新生儿细菌感染的早期诊断和临床转归中意义。方法用ELISA测定三组血清细胞因子的水平。感染组:21例细菌感染新生儿(治疗前和有效治疗后);非感染组:20例非感染性疾病新生儿;脐血组:30例正常新生儿。结果感染组IL-8和IL-13水平较非感染组升高(P<0.05);感染组治疗后IL-8水平较治疗前下降。结论新生儿细菌感染时血清IL-8和IL-13显著升高,可作为新生儿细菌感染的早期诊断指标,IL-8可用来评价疗效。     

Comparison of procalcitonin with C-reactive protein, interleukin 6 and interferon-alpha for differentiation of bacterial vs. viral infections.

BACKGROUND: Procalcitonin (PCT) concentration increases in bacterial infections but remains low in viral infections and inflammatory diseases. The change is rapid and the molecule is stable, making it a potentially useful marker for distinguishing between bacterial and viral infections. METHODS: PCT concentration was determined with an immunoluminometric assay on plasma collected at admission in 360 infants and children hospitalized for bacterial or viral infection. It was compared with C-reactive protein (CRP), interleukin 6 and interferon-alpha measured on the same sample. RESULTS: The mean PCT concentration was 46 microg/l (median, 17.8) in 46 children with septicemia or bacterial meningitis. PCT concentration was > 1 microg/l in 44 of 46 in this group and in 59 of 78 children with a localized bacterial infection who had a negative blood culture (sensitivity, 83%). PCT concentration was > 1 microg/l in 16 of 236 children with a viral infection (specificity, 93%). PCT concentration was low in 9 of 10 patients with inflammatory disease and fever. A CRP value > or =20 mg/l was observed in 61 of 236 patients (26%) with viral infection and in 105 of 124 patients (86%) with bacterial infection. IL-6 was > 100 pg/ml in 14% of patients infected with virus and in 53% with bacteria. A secretion of interferon-alpha was found in serum in 77% of viral infected patients and in 8.6% of bacterial infected patients. CONCLUSIONS: In this study a PCT value of 1 microg/l or greater had better specificity, sensitivity and predictive value than CRP, interleukin 6 and interferon-alpha in children for distinguishing between viral and bacterial infections. PCT values are higher in invasive bacterial infections, but the cutoff value of 1 microg/l indicates the severity of the disease in localized bacterial infection and helps to decide antibiotic treatment in emergency room. PCT may be useful in an emergency room for differentiation of bacterial vs. viral infections in children and for making decisions about antibiotic treatments.     

降钙素原和C-反应蛋白对儿童全身和局部细菌感染的诊断价值

目的 探讨降钙素原（PCT）和C-反应蛋白（CRP）对诊断全身和局部细菌感染的价值。方法 检索2011年1月至2012年6月在深圳市儿童医院住院病史系统中感染性疾病患儿的资料,分为全身细菌感染组（血培养阳性的严重脓毒症和败血症）,局部细菌感染组（急性化脓性扁桃体炎、泌尿系感染及化脓性骨关节炎）,病毒感染组（传染性单核细胞增多症和手足口病）。比较各组PCT、CRP水平和阳性率的差异。绘制受试者工作曲线（ROC）,计算曲线下面积（AUC）,评估PCT和CRP对全身和局部细菌感染的诊断价值。结果 148例患儿进入分析,全身细菌感染组19例,局部细菌感染组55例,病毒感染组74例。①CRP水平(mg·L-1)、PCT水平(μg·L-1)和PCT阳性率局部细菌感染组低于全身细菌感染组（CRP：21.35 vs 76.0,P＝0.001;PCT:0.10 vs 28.09, 32.7% vs 100%,P均<0.001）;CRP水平和阳性率局部细菌感染组高于病毒感染组（21.35 vs 4.0, 73.1% vs 27.0%, P均<0.001), PCT水平和阳性率局部细菌感染组与病毒感染组差异无统计学意义。3组WBC计数差异无统计学意义;WBC阳性率全身细菌感染组高于病毒感染组（84.5% vs 54.0%,P=0.017）,局部细菌感染组与全身细菌感染组、病毒感染组差异无统计学意义。②PCT水平和阳性率局部细菌感染合并全身炎症反应综合征（SIRS）患儿显著高于不合并SIRS者（0.40 vs 0.08,P＝0.002;60.0% vs 17.1%, P＝0.001）,CRP水平和阳性率无显著差异。③PCT和CRP诊断全身细菌感染的ROC AUC分别为0.99和0.84;诊断局部细菌感染的ROC AUC分别为0.54和0.78。结论 PCT是识别全身细菌感染和监测局部细菌感染进展而合并SIRS的敏感指标。鉴别局部细菌感染时,CRP较PCT敏感。     

血降钙素原在儿童化脓性脑膜炎与病毒性脑膜炎中的变化

目的：化脓性脑膜炎病原学检出率较低,尤其脑脊液改变不典型时给临床诊断带来困难。已证实血降钙素原(PCT)测定对鉴别细菌与病毒感染有重要价值,但在化脓性脑膜炎与病毒性脑膜炎的鉴别诊断方面与CRP、血沉比较孰优孰劣未见报道,另外诊断化脓性脑膜炎时PCT临界值的确定也未见报道。该文通过血PCT测定并与CRP、血沉比较探讨其对儿童化脓性脑膜炎与病毒性脑膜炎的鉴别诊断意义。方法：用免疫荧光法测定了41例急性脑膜炎患儿血PCT(其中化脓性脑膜炎18例,病毒性脑膜炎23例),同时测定血CRP、血沉。结果：化脓性脑膜炎组PCT,CRP及血沉分别为51.73±30.75μg/L,182.36±54.5mg/L和50.44±8.95mm/h;明显高于病毒性脑膜炎组0.84±0.99μg/L,8.90±10.66mg/L和16.75±13.23mm/h(P<0.01),受试者工作特征曲线下面积PCT为0.984(95%可信区间0.953～1.013),而CRP为0.983(95%可信区间0.954～1.012),二者比较差异无显著性(P>0.05)。有2例病毒性脑膜炎PCT值高于0.5μg/L,而化脓性脑膜炎病人均高于此值。结论：血PCT同CRP在儿童化脓性脑膜炎与病毒性脑膜炎的鉴别诊断方面有重要参考价值,优于血沉。     

Procalcitonin, C-reactive protein and leukocyte count in children with lower respiratory tract infection

BACKGROUND: Lower respiratory tract infection is the most common infection leading to unnecessary antibiotic treatment in children. Etiologic diagnosis is not immediately achieved, and the pathogen remains unidentified in a large number of cases. Neither clinical nor laboratory factors allow for a rapid distinction between bacterial and viral etiology. The aim of our study was to evaluate the reliability of procalcitonin (PCT), C-reactive protein (CRP) and leukocyte count in distinguishing pneumococcal, atypical and viral lower respiratory tract infection. METHODS: PCT, CRP and leukocyte count were measured in children with microbiologically documented diagnoses of lower respiratory tract infection. The results were compared of children with pneumococcal, atypical and viral etiologies. RESULTS: PCT and CRP showed significant correlation with a bacterial etiology of lower respiratory tract infection. No significance was found for leukocyte count. Using a cutoff point of 2 ng/ml for PCT and 65 mg/l for CRP, the sensitivities and specificities for distinguishing bacterial from viral lower respiratory tract infections were 68.6 and 79.4% for PCT and 79.1 and 67.1% for CRP. The sensitivities and specificities for distinguishing pneumococcal from other etiologies were 90.3 and 74.1% for PCT and 90.3 and 60% for CRP, respectively. CONCLUSIONS: High PCT and CRP values show a significant correlation with the bacterial etiology of lower respiratory tract infection. PCT and CRP show good sensitivity for distinguishing pneumococcal from other etiologies. PCT shows higher specificity than CRP. PCT and CRP can help make decisions about antibiotic therapy in children with lower respiratory tract infections.     

C反应蛋白与小儿呼吸道感染关系的meta分析

目的 探讨C反应蛋白(CRP)与小儿细菌性和病毒性呼吸道感染的关系和意义.方法 采用meta分析方法对国内相关文献进行定量综合分析.结果 符合纳入标准的有13个研究.血清ClIP含量细菌感染组(A组)比病毒感染组(B组)高,95%CI:2.33～3.94,细菌感染组比对照组(C组)高,95%CI:2.44～3.60,而病毒感染组比对照组高,95%CI:0.40～0.96.结论 血清CRP含量的增高有助于临床对细菌感染的早期诊断,以减少抗生素的滥用.     

C reactive protein in the evaluation of febrile illness.

We studied prospectively 154 febrile children to determine the diagnostic value of the quantitative serum C reactive protein concentrations (CRP). Children with acute otitis media, acute tonsillitis, or treated with antibiotics during the two previous weeks and infants less than 2 months of age were excluded. Ninety seven children were from private paediatric practice and 57 were patients who had been admitted to hospital. The comparison group consisted of 75 children with confirmed bacterial infections whose CRP values were recorded retrospectively. In the study group 35 (23%) children had a confirmed viral infection, 92 (59%) had a probable viral infection as judged from the clinical picture and outcome of the illness, and 27 (18%) had a bacterial or probable bacterial infection. When the duration of the disease was more than 12 hours and the CRP value less than 20 mg/l, all children had a confirmed or probable viral infection. Nine children (one from the study group and eight from the comparison group) were found to have a septic infection and a CRP value of 20 mg/l or less. In all these cases, however, the duration of the symptoms was less than 12 hours. In addition CRP less than or equal to 20 mg/l was found in five (14%) children with urinary tract infection in the comparison group. CRP values of 20-40 mg/l were recorded in children with both viral and bacterial infections. A CRP value greater than or equal to 40 mg/l detected 79% of bacterial infections with 90% specificity. Our data show that determination of serum CRP concentrations is a valuable tool in evaluating children who have been ill for more than 12 hours.     

Procalcitonin in pediatric emergency departments for the early diagnosis of invasive bacterial infections in febrile infants: results of a multicenter study and utility of a rapid qualitative test for this marker

BACKGROUND: Procalcitonin (PCT) is a potentially useful marker in pediatric Emergency Departments (ED). The basic objectives of this study were to assess the diagnostic performance of PCT for distinguishing between viral and bacterial infections and for the early detection of invasive bacterial infections in febrile children between 1 and 36 months old comparing it with C-reactive protein (CRP) and to evaluate the utility of a qualitative rapid test for PCT in ED. METHODS: Prospective, observational and multicenter study that included 445 children who were treated for fever in pediatric ED. Quantitative and qualitative plasma values of PCT and CRP were correlated with the final diagnosis. To obtain the qualitative level of PCT the BRAHMS PCT-Q rapid test was used. RESULTS: Mean PCT and CRP values in viral infections were 0.26 ng/ml and 15.5 mg/l, respectively. The area under the curve obtained for PCT in distinguishing between viral and bacterial infections was 0.82 (sensitivity, 65.5%; specificity, 94.3%; optimum cutoff, 0.53 ng/ml), whereas for CRP it was 0.78 (sensitivity, 63.5%; specificity, 84.2%; optimum cutoff, 27.5 mg/l). PCT and CRP values in invasive infections (PCT, 24.3 ng/ml; CRP 96.5 mg/l) were significantly higher than those for noninvasive infections (PCT, 0.32 ng/ml; CRP, 23.4 mg/l). The area under the curve for PCT was 0.95 (sensitivity, 91.3%; specificity, 93.5%; optimum cutoff, 0.59 ng/ml), significantly higher (P < 0.001) than that obtained for CRP (0.81). The optimum cutoff value for CRP was >27.5 mg/l with sensitivity and specificity of 78 and 75%, respectively. In infants in whom the evolution of fever was <12 h (n = 104), the diagnostic performance of PCT was also greater than that of CRP (area under the curve, 0.93 for PCT and 0.69 for CRP; P < 0.001). A good correlation between the quantitative values for PCT and the PCT-Q test was obtained in 87% of cases (kappa index, 0.8). The sensitivity of the PCT-Q test (cutoff >0.5 ng/ml) for detecting invasive infections and differentiating them from noninvasive infections was 90.6%, with a specificity of 83.6%. CONCLUSIONS: PCT offers better specificity than CRP for differentiating between the viral and bacterial etiology of the fever with similar sensitivity. PCT offers better sensibility and specificity than CRP to differentiate between invasive and noninvasive infection. PCT is confirmed as an excellent marker in detecting invasive infections in ED and can even make early detection possible of invasive infections if the evolution of the fever is <12 h. The PCT-Q test has a good correlation with the quantitative values of the marker.     

中性粒细胞CD64和降钙素原联合检测在新生儿细菌感染早期诊断中的价值

目的探讨血清中性粒细胞CD64和降钙素原(PCT)联合检测在新生儿细菌感染早期诊断中的价值。方法将37例细菌感染新生儿依据出院诊断分为败血症组(n=15)和一般感染组(非败血症患儿;n=22);并选取同期住院非感染新生儿作为对照组(n=21)。各组新生儿均于入院后即刻抽取静脉血,采用流式细胞术检测血清中性粒细胞CD64表达,化学发光法和免疫透射比浊法分别检测血清PCT及CRP水平。结果败血症组血清中性粒细胞CD64、PCT、CRP水平高于对照组(P0.01);一般感染组中性粒细胞CD64水平高于对照组(P0.01);败血症组血清PCT、CRP水平高于一般感染组(P0.01)。中性粒细胞CD64、PCT、CRP诊断细菌感染的曲线下面积分别为0.818、0.818、0.704,均低于中性粒细胞CD64与PCT联合诊断细菌感染的曲线下面积(0.926)。中性粒细胞CD64与PCT联合检测在早期诊断新生儿感染的灵敏度和准确度分别为97.29%和89.65%,较CRP联合中性粒细胞CD64或PCT检测的灵敏度和准确度均高,较中性粒细胞CD64、PCT及CRP单项检测的灵敏度和准确度更高。结论中性粒细胞CD64、PCT联合检测能显著提高新生儿细菌感染诊断的灵敏度及准确度,有助于早期识别细菌感染。     

C反应蛋白及降钙素原在小儿脓毒症血流感染及其他部位感染性疾病中的诊断价值

目的：评估入住PICU 6 h内血清CRP及PCT水平在脓毒症血流感染及其他部位感染患儿临床诊断中的价值。方法：回顾性分析2010年1月至2012年1月期间,中国医科大学附属盛京医院PICU收治的30名明确诊断SIRS患儿,脓毒症血流感染及脓毒症其他部位感染患儿各15名,收集入住6 h内的血清CRP、PCT及D-二聚体含量资料,进行差异性比较并通过ROC曲线分析其诊断价值。结果：脓毒症血流感染组患儿的血清CRP及PCT水平较脓毒症其他部位感染组显著升高（P0.05）。血清PCT水平较CRP水平在诊断与鉴别脓毒症血流感染与其他部位感染性疾病方面有明显优势,PCT10 ng/mL时诊断脓毒症血流感染具有较高的可信度（阳性预测值：77%）。结论：入院6 h内的血清PCT水平较CRP水平在早期鉴别入住PICU脓毒症血流感染与其他部位感染患儿具有更好的诊断价值;当血清PCT水平>10 ng/mL时,脓毒症血流感染的诊断可能性较大。     

Procalcitonin in children admitted to hospital with community acquired pneumonia.

AIMS: To assess the sensitivity, specificity, and predictive value of procalcitonin (PCT) in differentiating bacterial and viral causes of pneumonia. METHODS: A total of 72 children with community acquired pneumonia were studied. Ten had positive blood culture for Streptococcus pneumoniae and 15 had bacterial pneumonia according to sputum analysis (S pneumoniae in 15, Haemophilus influenzae b in one). Ten patients had Mycoplasma pneumoniae infection and 37 were infected with viruses, eight of whom had viral infection plus bacterial coinfection. PCT concentration was compared to C reactive protein (CRP) concentration and leucocyte count, and, if samples were available, interleukin 6 (IL-6) concentration. RESULTS: PCT concentration was greater than 2 microg/l in all 10 patients with blood culture positive for S pneumoniae; in eight of these, CRP concentration was above 60 mg/l. PCT concentration was greater than 1 microg/l in 86% of patients with bacterial infection (including Mycoplasma and bacterial superinfection of viral pneumonia). A CRP concentration of 20 mg/l had a similar sensitivity but a much lower specificity than PCT (40% v 86%) for discriminating between bacterial and viral causes of pneumonia. PCT concentration was significantly higher in cases of bacterial pneumonia with positive blood culture whereas CRP concentration was not. Specificity and sensitivity were lower for leucocyte count and IL-6 concentration. CONCLUSIONS: PCT concentration, with a threshold of 1 microg/l is more sensitive and specific and has greater positive and negative predictive values than CRP, IL-6, or white blood cell count for differentiating bacterial and viral causes of community pneumonia in untreated children admitted to hospital as emergency cases.