利用核素99mTc-sestamibi运动心肌显像评价冠状动脉PTCA及PTCA联合stent术后再狭窄

目的　通过分析99mTc sestamibi核素运动心肌灌注断层显像 (SPECT)评价冠心病患者冠状动脉PTCA疗效。方法　 4 5例冠心病患者 ,PTCA术后 1～ 2 4个月 ,静脉注射放射性示踪剂99mTc sestamibi,定性观察运动和静态心肌血流灌注情况 ,并行冠状动脉造影 ,利用 χ2 检验等评价冠心病患者单纯PTCA术与PTCA结合stent支架介入治疗疗效和运动心肌显像判断冠状动脉再狭窄情况。结果　①PTCA术后 (包括Stent支架介入治疗 ) ,约 2 6 7%的患者出现术后再狭窄 ,并且再狭窄高峰时间发生在术后 2～ 3个月之内 ;②单纯PTCA术后冠脉血管再狭窄占狭窄总数 83 3% ,PTCA结合Stent支架介入治疗后血管再狭窄约占狭窄总数 16 7% ,两种方法有显著性差异 (P <0 .0 5 ) ;③以冠状动脉造影为参照 ,99mTc sestamibi运动心肌断层显像判断术后冠脉再狭窄灵敏性和特异性分别为 76 9%和 95 0 %。结论　99mTc sestamibi运动心肌灌注断层显像可用于评价PTCA或 /和stent介入治疗。     

~(99)Tc~m-MIBI运动-静息心肌灌注断层显像检测PTCA治疗后再狭窄临床价值

目的　评价 99Tcm- MIBI运动 -静息心肌显像预测经皮腔内冠状动脉成形术 (PTCA )再狭窄临床价值。方法　回顾分析 PTCA后有运动 /静息心肌灌注显像和冠状动脉造影资料完整的 6 0例确诊为冠心病病人 ,根据是否有心肌梗死分两组 ,分析心肌灌注显像结果 ,并与冠状动脉造影结果对比。结果　 99Tcm- MIBI运动 -静息心肌断层显像预测再狭窄的敏感性和特异性分别为 79% ,90 % ,对左前降支 ,左回旋支 ,右冠状动脉再狭窄预测的敏感性和特异性分别为 74～ 84 % ,5 3～ 90 % ,5 0～ 6 0 %。结论　 99Tcm- MIBI运动 -静息心肌灌注断层显像是预测 PTCA术后再狭窄较特异的方法。     

多巴酚丁胺负荷~(99m)Tc-MIBI门控心肌灌注断层显像诊断冠心病的价值

为评价药物负荷核素心肌显像诊断冠心病的价值 ,选取胸痛可疑冠心病患者 5 5例 ,其中男性 39例 ,女性 16例 ,年龄 84±10岁。全部患者行多巴酚丁胺负荷99mTc MIBI门控心肌灌注断层显像 (DBA SPECT) ,对其中 2 0例患者行冠状动脉造影。以上三种检查均于三周内完成。结果发现 ,冠状动脉未见显著狭窄 12例 (≤ 5 0 %) ,其中 1例示心肌桥 ,1例示回旋支 30 %狭窄 ,1例示右冠状动脉 5 0 %狭窄。显著狭窄共 8例 (>5 0 %) ,其中单支病变 4例 ,双支病变 3例 ,3支病变 1例。 40 %的患者DBA SPECT结果呈可逆性放射性稀疏 (即心肌缺血改变 )。 2 0例冠状动脉造影患者中 ,DBA SPECT诊断冠心病的灵敏度为 87.5 %,特异性为 75 %,准确率为 80 %。结果提示 ,DBA SPECT是诊断冠心病的一种具有高敏感性及特异性的非创伤性方法 ,尤其对于不能耐受运动负荷及 /或有支气管哮喘、慢性阻塞性肺气肿等潘生丁、腺苷禁忌症的患者是一种安全可靠的诊断方法。     

多巴酚丁胺负荷201Tl心肌断层显像对冠状动脉病变的诊断

目的 :探讨多巴酚丁胺 (DOB)负荷 2 0 1Tl心肌单光子发射计算机断层显像对冠状动脉病变的诊断价值。方法 :对 70例临床确诊或疑诊冠心病的患者在冠状动脉造影前后 2周内进行 DOB负荷 2 0 1Tl心肌断层显像。结果 :DOB2 0 1Tl心肌断层显像诊断冠心病的敏感性为 93.3% ,特异性为80 .0 % ;单、双、三支冠状动脉受累时的敏感性为 90 .9%、93.7%、10 0 % ;心肌显像对左前降支、回旋支和右冠状动脉病变诊断的敏感性和特异性分别为 6 8.5%、75.0 % ,4 2 .9%、97.6 %和 81.6 % ,87.5%。负荷试验终点时双支、三支血管病变 DOB用量明显低于单支病变用量 (P <0 .0 1)。试验中未见严重不良反应。结论 :DOB2 0 1Tl心肌断层显像对冠状动脉病变有一定的诊断价值     

冠状动脉造影与运动负荷心肌灌注显像诊断冠心病的对比分析

目的 :比较冠状动脉造影 (CAG)和运动负荷心肌灌注显像对诊断冠心病 (CHD)的作用。方法 :2 35例患者在 1个月内进行了CAG和运动负荷99mTc MIBI心肌灌注单光子发射计算机断层显像 (SPECT)检查。CAG在主要血管及分支病变狭窄≥ 5 0 %为阳性 ;心肌灌注检查将左室分为 16个节段 ,运动态和静息态相比较 ,存在放射性缺损或填充为阳性。结果 :2 35例中CHD170例 ,其他心脏病 4 3例 ,无器质性心脏病 2 2例。 170例CHD中 ,16 8例CAG阳性 ,16 2例运动SPECT阳性。 4 3例其他心脏病中 13例运动SPECT阳性 (30 .2 % )。 2 2例无器质性心脏病病例中 3例运动SPECT阳性 (13.6 % )。在CHD的诊断中 ,CAG的敏感性为 98.8% ;运动SPECT敏感性为95 .3% ,特异性为 86 .4 %。结论 :在临床工作中 ,CAG和运动SPECT均为诊断CHD的有效手段。由于后者的无创性 ,易于重复 ,是临床随访的较好方法。但在其他心脏病患者 ,运动SPECT阳性率可达 30 .2 % ;在无明显心脏疾病者可达 13.6 %。因此 ,临床上有必要鉴别运动SPECT阳性的非CHD患者     

经皮腔内冠状动脉成形术后的临床及冠状动脉造影随访

我国目前对经皮腔内冠状动脉成形术(PTCA)术后再狭窄的资料报道较少.本研究对592例PTCA成功的病人(男503例、女89例,平均年龄58.4±9.1岁)进行术后临床及冠状动脉造影随访.记录临床症状的复发,Holter动态心电图监测,次极量心电图运动试验和~(99m)Tc-MIBI动态心肌灌注显像手术后3个月、6个月和半年的结果.其中62例病人平均手术后10.4±7.6个月进行冠状动脉造影随访.并以冠状动脉造影的结果将此62例病人分为再狭窄组(35例)和无再狭窄组(27例),观察心绞痛症状和三种无创性检查对再狭窄预测的特异性和敏感性.结果表明:心绞痛症状、Holter动态心电图、次极量心电图运动试验和~99mTc-MIBI心肌灌注显像对再狭窄诊断的特异性和敏感性分别为75.7%和72.0%;71.4%和86.7%;66.7%和73.1%;76.5%和83.3%.如果结合临床症状和三种无创性检查组成综合缺血指标,对PTCA术后再狭窄诊断的特异性和敏感性可进一步提高,分别为85.2%和92.9%.本文对PTCA术后临床症状,无创性检查和冠状动脉造影的随访可能对今后国内大规模临床随访提供有益的参考.     

045 运动性核素心肌灌注显像诊断冠心病研究进展

运动性核素心肌灌注显像在检测冠心病、评价心脏病变程度等方面已取得许多进展,现摘要概述如下. 定量单光子发射型计算机断层显像(SPECT)是心肌灌注显像的重要进展.有研究以SPECT检查1 447例冠心病(CAD)患者,其敏感性平均为92%(82%～98%)、特异性为68%(44%～91%).SPECT检测CAD的特异性低的原因,可能与扫描异常者做冠脉造影检查比扫描正常者多有关.饶有兴趣的是,SPECT检测既往无心肌梗死者CAD的敏感性仍高达85%.SPECT201铊(201Tl)显像检测1支、2支和3支冠脉病变的敏感性分别平均为83%、93%和95%.使SPECT201Tl显像检测CAD敏感性降低的主要因素有1支冠脉病变、左旋支狭窄、冠脉分支或远端狭窄、内径狭窄50%～70%的轻度冠脉狭窄、由非心脏症状所致停止运动时的不适当心率反应、应用硝酸盐类或钙通道阻滞剂治疗的心绞痛等.因此,应提高检测既往有心肌梗死、广泛性冠脉病变、高度冠脉狭窄、近端冠脉狭窄、局部室壁运动异常患者的敏感性.在这方面,定量扫描分析的敏感性和特异性要比应激试验和再分布201Tl闪烁图视觉评价的敏感性高. 由于201Tl闪烁法不能识别假稀疏图像,故其总敏感性并不十分理想.虽然定量201Tl显像的敏感性有所提高,但假阳性率仍然较高.在心尖部到心底部常观察到假阳性缺损.女性由于乳房组织的覆盖,前壁和室间隔等部位可出现假稀疏图像.高位横膈可造成下壁假阳性缺损.门电路99m锝(99mTc)灌注显像,可在断层X线照相SPECT上评价从舒张末期至收缩末期的收缩期室壁厚度.识别低灌注区域正常的收缩期室壁厚度,并可确定缺损是假稀疏而不是心肌疤痕.以门电路断层X线照相评价时,后者最可能伴有收缩期室壁厚度变小.Taillefer等的前瞻性研究评价了201Tl和99mTc灌注显像检测女性CAD的准确性.该研究中许多患者做过冠脉造影,检测明显CAD的总敏感性201Tl和99mTc相仿.然而,201Tl或99mTc-sestamibi(99mTc-MIBI)灌注显像、门电路99mTc-MIBI SPECT显像检测冠脉内径狭窄≥50%者的特异性分别平均为70.6%、86.3%和94.1%(P=0.05、P=0.002);检测冠脉内径狭窄≥70%者的特异性分别平均为67.2%、84.4%和92.2%.201Tl的特异性显著低于99mTc-MIBI和门电路99mTc-MIBI(P=0.02、P=0.0004),99mTc-MIBI灌注显像和门电路99mTc-MIBI SPECT显像两者间则无显著差异. 对运动性99mTc-MIBI SPECT显像研究的集中分析表明,99mTc-MIBI和201Tl检测CAD的敏感性分别为90%和83%,特异性分别为93%和80%,正常化比率99mTc-MIBI为100%、201Tl为77%.静息201Tl/应激99mTc-MIBI SPECT显像双重同位素检查,可从非可逆性缺损中识别可逆性缺损.该方案于静息时注射3.5mCi201Tl,10min后获得显像;获得这些静息性显像后立即进行运动试验,于运动高峰时注射25～30mCi99mTc-MIBI.Berman等报道这一方法检测CAD的敏感性和特异性分别为91%和75%.预试验时CAD可能性低者的正常化比率为95%.静息性201Tl/ 99mTc-MIBI闪烁图的可逆行缺损检出率与标准静息性201Tl/ 99mTc-MIBI SPECT显像相仿.最近的研究显示,新型99mTc标记灌注剂99mTc-N-NOET,首次通过心肌摄取指数比99mTc-MIBI或99mTc-tatrofosmin高,分布时间与201Tl相仿. (陈清江摘)     

ATP负荷及运动负荷试验中心电图的变化对冠心病的诊断价值

目的探讨ATP负荷及运动负荷心肌灌注单光子发射计算机体层摄影术(SPECT)中的ECG变化及其对冠心病的诊断价值。方法选择61例疑诊冠心病的患者,并在不同时间分别行ATP负荷及运动负荷SPECT检查,其中46例行冠状动脉造影。收集ATP及运动负荷试验中的ECG资料并进行分析。结果ATP与运动负荷试验中ECG心律失常的发生情况相似(χ2=1.985,P=0.159);ATP负荷试验ST段下降发生率明显低于运动负荷试验(12.5%vs51.8%,χ2=19.813,P<0.001),且下降幅度低。ATP负荷试验ECG诊断冠心病的敏感性明显低于运动负荷试验(28.6%vs71.4%,χ2=7.714,P=0.005),特异性、阳性预测值及阴性预测值与运动负荷试验相似(95.2%vs71.4%,85.7%vs71.4%,57.1%vs71.4%,P>0.05)。结论与运动负荷试验比较,ATP负荷试验ECG诊断冠心病的敏感性低,但特异性及阳性预测值相对较高。     

三磷酸腺苷负荷单光子发射型计算机断层摄影术心肌灌注显像对经皮冠状动脉腔内成形术的疗效评价

目的探讨三磷酸腺苷(ATP)负荷单光子发射型计算机断层摄影术(SPECT)心肌灌注显像在评价冠心病患者经皮冠状动脉腔内成形术(PTCA)疗效中的作用.方法冠心病患者62例,依临床特点及SPECT显像分为2组,单纯心肌缺血组22例及心肌梗塞伴缺血组40例.ATP按0.28mg/(kg@min)的速度匀速泵入共5min行SPECT检查,观察PTCA前后心肌各心室壁节段放射性异常积分及靶心图缺损范围的变化.结果ATP负荷SPECT检查副作用轻、消失快,耐受性好;PTCA术后放射性异常积分降低及靶心图范围缩小说明近期缺血改善明显;术前心肌灌注显像示缺血严重、范围广的心室节段,其相关血管多为"罪犯”血管;PTCA术后3～6个月,10例患者发现再缺血,经冠状动脉造影证实有再狭窄发生.结论ATP负荷SPECT为评价冠心病患者PTCA疗效及探测术后再狭窄的安全而准确的方法并有助于术前选择病变血管.     

心脏磁共振与核医学负荷心肌灌注显像探测冠心病心肌缺血的对比研究

目的:对比心脏磁共振成像(CMR)与核医学单光子计算机断层扫描(SPECT)负荷心肌灌注显像探测冠心病心肌缺血的诊断效能。方法:前瞻性入选51例疑似或确诊冠心病患者,所有患者在冠状动脉造影(CAG)检查之前或之后4周内进行了CMR和SPECT负荷心肌灌注显像,三种检查之间无任何再血管化治疗。以CAG作为参考标准,将CMR与SPECT分析结果进行比较,计算其诊断效能。结果:基于患者个体分析,CMR和SPECT负荷心肌灌注成像检测狭窄50%以上冠状动脉的敏感性及特异性分别为:90%和75%;74%和75%。CMR的诊断效能0.879,与SPECT 0.818相似(P=0.3377);基于血管分析,CMR和SPECT负荷心肌灌注成像检测狭窄50%以上冠状动脉的敏感性及特异性分别为:78%和83%;75%和86%。CMR的诊断效能0.827,略好于SPECT 0.767(P=0.1284)。其中基于分支血管进行分析,CMR探测左前降支(LAD)分支血管病变的诊断效能0.849好于SPECT 0.688(P=0.0141)。CMR探测左旋支及右冠状动脉分支血管的诊断效能与SPECT相似,两者间差异无统计学意义。结论:CMR与SPECT负荷心肌灌注成像均能有效检测冠心病心肌缺血,基于患者个体分析,CMR与SPECT相比敏感性高,特异性相同;基于血管分析,CMR的敏感性和特异性均好于SPECT,尤其对于LAD分支血管病变。     

胰岛素瘤的解剖分布特点分析

目的胰岛素瘤是最常见的胰腺神经内分泌肿瘤，因其临床表现多样，导致诊断困难。影像学诊断尤其是超声内镜(EUS)在胰岛素瘤的诊断中起着重要作用，拥有较高的敏感性和特异性。本研究拟通过明确胰岛素瘤的解剖分布特点，以期有助于提高影像学的诊断准确率和降低漏诊率，尤其是在教育和培训实践中对于EUS的学习者更具有指导价值。 方法回顾性分析解放军总医院第一医学中心病案资料数据库1993年1月至2019年11月经外科手术、病理确诊为胰岛素瘤的患者的临床资料，检索方法采取搜索术后病理诊断为"胰岛素瘤"的病例，通过查阅病例的方法，提取出胰岛素瘤的大小和解剖分布等数据，进一步分析其特点。 结果共检索到确诊为胰岛素瘤的患者116例，其中，男45例、女71例，年龄13～76岁，平均年龄(44.4±14.85)岁。胰岛素瘤单发110例(94.8%)、多发6例(5.2%)。位置分布：头颈部46例(39.7%)，单发45例、多发1例；体尾部68例(58.6%)，单发65例、多发3例；全胰腺多发2例(1.7%)。病变大小特点：最大径0.4～3.4 cm，平均大小(1.53±0.58)cm。≤1 cm 29例、>1 cm而≤1.5 cm41例、>1.5 cm而≤2.0 cm28例，≤3 cm 15例，>3 cm 3例。年龄与肿瘤的大小相关，≤44岁患者肿瘤平均大小为(1.36±0.51)cm、>44岁患者肿瘤平均大小为(1.70±0.60)cm，P<0.05。头颈部的肿瘤大于体尾部的肿瘤，头颈部肿瘤平均大小(1.66±0.63)cm，体尾部(1.42±0.52)cm，P<0.05。 结论胰岛素瘤在胰腺体尾部较头颈部更好发；绝大多数单发，但可以全胰腺多发；多数小于1.5 cm，肿瘤的大小与患者年龄和肿瘤的解剖分布相关。     

Pathogenesis of carcinoma of the papilla of Vater

Most adenomas and carcinomas of the small intestine and extrahepatic bile ducts arise in the region of the papilla of Vater. In familial adenomatous polyposis (FAP) it is the main location for carcinomas after proctocolectomy. In many cases symptoms due to stenosis lead to diagnosis at an early tumor stage. In about 80%, curative intended resection is possible. Operability is the most relevant prognostic factor. Most ampullary carcinomas resp. carcinomas of the papilla of Vater develop from adenomatous or flat dysplastic precursor lesions. They can be sited in the ampulloduodenal part of the papilla of Vater, which is lined by intestinal mucosa. They also can develop in deeper parts of the ampulla, which are lined by pancreaticobiliary duct mucosa. Intestinal-type adenocarcinoma and pancreaticobiliary-type adenocarcinoma represent the main histological types of ampullary carcinoma. Furthermore, there exist unusual types and undifferentiated carcinomas. Many carcinomas of intestinal type express the immunohistochemical marker profile of intestinal mucosa (keratin 7?, keratin 20+, MUC2+). Carcinomas of pancreaticobiliary type usually show the immunohistochemical profile of pancreaticobiliary duct mucosa (keratin 7+, keratin 20?, MUC2?). Even poorly differentiated carcinomas, as well as unusual histological types, may conserve the marker profile of the mucosa they developed from. These findings underline the concept of histogenetically different carcinomas of the papilla of Vater which develop either from intestinal- or from pancreaticobiliary-type mucosa of the papilla of Vater. Molecular alterations in ampullary carcinomas are similar to those of colorectal as well as pancreatic carcinomas, although they appear at different frequencies. In future studies, molecular alterations in ampullary carcinomas should be correlated closely with the different histologic tumor types. Consequently, the histologic classification should reflect the histogenesis of ampullary tumors from the two different types of papillary mucosa.     

Demonstration of the mechanism of action of biguanides

Summary Palmitic acid oxidation in rat diaphragm homogenate is depressed by biguanide concentrations that are still incapable of inhibiting oxidative phosphorylation. Glucose oxidation is not directly effected by the same biguanide concentrations: however, the inhibitory effect of palmitic acid on glucose oxidation is partly removed by biguanides. Inhibition of fatty acid oxidation, which accounts for most of the metabolic effects caused by these drugs, can be regarded as the fundamental mechanism of action of biguanides. There is some evidence suggesting that these drugs might interact with carnitine, thus preventing long-chain fatty acids from being transported across the mitochondrial membrane to the site of oxidation. Traduzione a cura degli AA.     

Lack of correlation of degree of villous atrophy with severity of clinical presentation of coeliac disease

BACKGROUND AND AIM: Both the clinical presentation and the degree of mucosal damage in coeliac disease vary greatly. In view of conflicting information as to whether the mode of presentation correlates with the degree of villous atrophy, we reviewed a large cohort of patients with coeliac disease. PATIENTS AND METHODS: We correlated mode of presentation (classical, diarrhoea predominant or atypical/silent) with histology of duodenal biopsies and examined their trends over time. RESULTS: The cohort consisted of 499 adults, mean age 44.1 years, 68% females. The majority had silent coeliac disease (56%) and total villous atrophy (65%). There was no correlation of mode of presentation with the degree of villous atrophy (p=0.25). Sixty-eight percent of females and 58% of males had a severe villous atrophy (p=0.052). There was a significant trend over time for a greater proportion of patients presenting as atypical/silent coeliac disease and having partial villous atrophy, though the majority still had total villous atrophy. CONCLUSIONS: Among our patients the degree of villous atrophy in duodenal biopsies did not correlate with the mode of presentation, indicating that factors other than the degree of villous atrophy must account for diarrhoea in coeliac disease.     

血吸虫童虫生长发育及其机制的研究进展

血吸虫童虫是宿主免疫系统攻击的重要靶标,包括皮肤型、肺型和肝门型童虫。宿主分子对童虫生长发育具有重要作用。童虫生长发育机制包括免疫调节、信号转导、性别发育及凋亡等。肌动蛋白、组织蛋白酶、烯醇化酶和葡萄糖基转移酶等分子为血吸虫童虫生长发育的重要分子。本文对血吸虫童虫生长发育及其机制的研究进展做一综述。     

氯硝柳胺悬浮剂的毒性评价

目的评价氯硝柳胺悬浮剂的毒性，为现场大规模应用灭螺提供依据。方法按照中华人民共和国国家标准GB 15670-1995《农药登记毒理学试验方法》和鱼类毒性试验方法进行。结果经口、经皮肤的LDso雌、雄性大鼠均>5 000 mg/kg，经呼吸道的LCso雌、雄性大鼠均>5 000mg/m3，该药经口、经皮肤、经呼吸道毒性均属微毒类药物；兔眼用药后，观察期内无不良反应，对眼无刺激性；皮肤用药后对皮肤无刺激性。与氯硝柳胺原药、氯硝柳胺乙醇胺盐原药和氯硝柳胺乙醇胺盐可湿性粉剂相比，氯硝柳胺悬浮剂对鱼急性毒性最低。结论氯硝柳胺悬浮剂属微毒类药物，对鱼的毒性低于其乙醇胺盐可湿性粉剂，适合于现场应用。     

124例耐多药结核分枝杆菌基因突变特征分析

目的对临床分离的耐多药结核分枝杆菌相关基因的突变特征进行分析。方法对124例耐多药结核分枝杆菌以及50株敏感株的耐药相关基因(包括异烟肼inh A、kat G、oxyR-ahp C间隔区以及利福平rpo B)进行序列测定,分析其基因突变情况。结果异烟肼耐药inh A基因突变率为14.5%;kat G基因突变率为70.2%(87/124),主要位于315位;oxyR-ahp C间隔区突变率为15.3%;inh A、kat G两种基因同时突变率75.0%,三种基因同时突变率为89.5%。利福平rpo B基因突变的检出率高达95.2%,突变主要发生在531、526、516位点。结论我省耐多药菌异烟肼耐药相关基因最常见突变为kat G 315、inh A C-T(-15)、axyR-ahp C间隔区(-10)C-T,利福平为rpo B531、526、516。结合MDR-TB耐药相关基因的特征分析,可以建立一种快速、准确、特异的适合于我省的检测结核菌耐多药性的新方法。     

Assessment of quality of life of parents of children with juvenile chronic arthritis

The aim of the study was to assess the quality of life (QOL) and the psychological status of parents of children with juvenile chronic arthritis (JCA). The QOL, anxiety and depression of the parents of 28 children with JCA were evaluated and compared to those of the parents of 28 healthy children. Mothers of JCA children and mothers of healthy children reported similar QOL. The reported anxiety and depression levels were similar for mothers and fathers in both groups. The parents of children with pauciarticular-type JCA reported lower QOL and higher levels of anxiety and depression than the parents of children with other types, namely polyarticular and systemic JCA. These findings may be explained by the fact that the pauciarticular patients had shorter disease duration and were less frequently seen in the outpatient clinic. The QOL of mothers of children with JCA was found to be slightly impaired in the group of children with pauciarticular JCA. Future larger studies are needed to confirm these results, as the number of subjects in the three groups was rather low. Received: 26 September 2001 / Accepted: 8 February 2002     

Numerical Simulation of the Effect of Rate of Change of Glucose on Measurement Error of Continuous Glucose Monitors

Background

A 5-day in-patient study designed to assess the accuracy of the FreeStyle Navigator® Continuous Glucose Monitoring System revealed that the level of accuracy of the continuous sensor measurements was dependent on the rate of glucose change. When the absolute rate of change was less than 1 mg•dl⁻¹•min⁻¹ (75% of the time), the median absolute relative difference (ARD) was 8.5%, with 85% of all points falling within the A zone of the Clarke error grid. When the absolute rate of change was greater than 2 mg•dl⁻¹•min⁻¹ (8% of the time), the median ARD was 17.5%, with 59% of all points falling within the Clarke A zone.

Method

Numerical simulations were performed to investigate effects of the rate of change of glucose on sensor measurement error. This approach enabled physiologically relevant distributions of glucose values to be reordered to explore the effect of different glucose rate-of-change distributions on apparent sensor accuracy.

Results

The physiological lag between blood and interstitial fluid glucose levels is sufficient to account for the observed difference in sensor accuracy between periods of stable glucose and periods of rapidly changing glucose.

Conclusions

The role of physiological lag on the apparent decrease in sensor accuracy at high glucose rates of change has implications for clinical study design, regulatory review of continuous glucose sensors, and development of performance standards for this new technology. This work demonstrates the difficulty in comparing accuracy measures between different clinical studies and highlights the need for studies to include both relevant glucose distributions and relevant glucose rate-of-change distributions.     

Study of constancy of hydrogen-consuming flora of human colon

The constancy of the hydrogen consuming flora of the human colon was studied in 15 healthy subjects via two measurements obtained 18 to 36 months apart. Hydrogen disappearance rate and the major products of H₂-consuming bacteria, methane and sulfide, were measured during incubation of fecal homogenates with excess hydrogen and sulfate. In 11/15, the hydrogen consumption rate and the predominant hydrogen-consuming pathway (methanogenesis, sulfate reduction, or neither) remained constant. However, major shifts in these pathways were observed in four subjects, with two losing and two gaining the ability to produce methane. Methanogenesis was associated with the highest hydrogen consumption rate. This study demonstrates that clinically unrecognizable, major alterations of the colonic flora occur in healthy subjects. Understanding of the factors responsible for these alterations might allow for therapeutic manipulation of the colonic flora.Supported in part by the Department of Veterans Affairs and NIDDKD RO1 DK 13309-25.