罗氏Cobas8000 e602检测促甲状腺激素的性能验证

目的 对Cobas8000 e602电化学发光免疫分析仪模块检测促甲状腺激素(TSH)的性能进行验证和评估.方法 参考美国临床和实验室标准协会(CLSI)的有关文件和相关文献,对Cobas8000免疫检测系统测定TSH的精密度、准确性、线性范围、参考区间及不同模块间检测结果的相关性进行验证分析.结果 TSH低值、高值批内精密度的结果分别为1.9%、1.3%,均≤1/4 CLIA′88 TEa,批间精密度为2.2%、1.5%,≤1/3 CLIA′88 TEa;能力验证实验成绩80%,准确度合格;线性范围为0.446~89.76μIU/mL,与试剂盒线性范围相符;参考区间符合实验室要求;模块间结果比对R2≥0.95符合要求.结论 Cobas8000检测系统的主要性能均达到相关标准的要求,能够满足临床需求.     

GP 1200干式荧光免疫定量分析仪检测PCT、SAA及IL-6项目性能评价

目的 对干式荧光免疫定量分析仪检测血清降钙素原(PCT)、淀粉样蛋白A(SAA)及白细胞介素6(IL-6)项目性能进行评价。方法 根据美国临床和实验室标准协会(CLSI)、国际标准化组织(ISO) 15189及ISO 17025相关文件，以DXI 800全自动化学发光免疫分析系统为参照，对GP 1200分析仪检测PCT、SAA及IL-6项目的精密度(CV)、正确度、携带污染率、灵敏度、线性及相关性进行评价。结果 GP 1200分析仪检测PCT、SAA及IL-6的CV分别为5.29%、7.57%及5.00%；低值PCT、SAA及IL-6的相对偏倚(Bias)分别为-0.71%、4.43%及10.39%，而高值PCT、SAA及IL-6的相对偏倚分别为-4.25%、6.29%及1.84%;PCT、SAA及IL-6的均值与理论值线性良好，相关系数(R²)分别为0.999、0.996及0.999，回归方程斜率(a)在0.960 5～1.100 3;PCT、SAA及IL-6检测携带污染率分别为0.089 4%、0.165 8%及0.018 4%；检测PCT、SAA及IL-6的...     

电化学发光法检测鳞状上皮细胞癌抗原的性能验证及与化学发光微粒子法检测的一致性评价

目的对罗氏Cobas e602电化学发光法检测鳞状上皮细胞癌抗原(SCCA)进行性能验证,并对电化学发光法和新产业Maglumi 2000 Plus化学发光微粒子法检测SCCA结果进行一致性评价。方法对电化学发光法检测SCCA的精密度、线性范围、稀释倍数、参考区间进行性能验证。用化学发光微粒子法和电化学发光法同时检测107例血清样本SCCA,对两种方法检测结果进行一致性评价。结果电化学发光法检测SCCA低值和高值的批内 CV 分别为2.4%和3.7%,批间 CV 分别为1.2%和1.6%;在0.32~68.26 ng/mL范围内线性良好, R 2 =0.9997;在1 ∶10和1 ∶20稀释倍数性能良好,临床可报告范围上限达到1400 ng/mL;20名表观健康者均在试剂盒给定的参考区间内(0~2.7ng/mL)。电化学发光法和化学发光微粒子法一致性评价结果显示,组内相关系数ICC=0.836,两种方法总体一致性良好;Bland- Altman偏差分析显示两种方法SCCA结果在低值部分(0~5.0ng/mL)一致性良好,随着SCCA浓度增加,偏差逐渐增大。结论罗氏Cobas e602电化学发光法检测SCCA的精密度、线性范围、稀释倍数、参考区间均符合检测要求。罗氏Cobas e602电化学发光法和新产业Maglumi 2000 Plus化学发光微粒子法检测SCCA在低值部分一致性良好,随着SCCA浓度升高,偏差逐渐增大。     

两种不同检测系统测定血清降钙素原的比较实验研究

目的 探讨三联生物微阵列化学发光检测系统测定血清降钙素原（PCT）结果的可靠性。方法 以罗氏Cobas e 601电化学发光检测系统为参照系统,三联生物微阵列化学发光检测系统为待评估系统,对血清PCT浓度进行测定并进行统计分析。结果罗氏电化学发光检测系统血清 PCT日内精密度的变异系数（CV）为5.33%~7.88%,日间CV为5.62%~8.56%。三联生物微阵列化学发光检测系统的日内CV为4.93%~7.28%,日间CV为5.47%~8.90%。两种检测系统有较好的相关性（回归方程y=1.174x+0.213,P＜0.05）,相关系数r2为0.997。在医学决定水平（PCT为0.50 ng/ml和2.0 ng/ml）处的Kappa值分别为0.878（P=4.60×10-7）和0.933（P=7.72×10-8）,阳性符合率分别为94.44%和100.00%,阴性符合率分别为93.33%和95.45%。结论 三联生物微阵列化学发光免疫分析法与罗氏电化学发光法测定血清PCT结果相关性和一致性好,可用于临床血清PCT的快速检测。     

基于我国WS/T促甲状腺激素受体抗体检测方法的性能验证

目的 基于我国卫生行业标准(WS/T)对迈瑞高敏磁微粒化学发光法(CLIA)检测TRAb进行性能验证。方法 参照最新WS/T文件,以Roche Cobase 601电化学发光法(ECLIA)作为已验证的检测方法,对迈瑞CLIA的精密度、基于患者血清的正确度、线性、检出限、参考区间进行验证,评价迈瑞与Roche的诊断符合率。结果 迈瑞CLIA检测TRAb的批内CV为1.56%～4.60%,实验室内CV为1.65%～5.19%;与Roche ECLIA的实验室相对差值为-3.6%;在0.02～44.00IU/L范围内线性拟合方程Y=1.040X+0.636,线性系数R²=0.990;24个检出限临界值数据22个(91.7%)≤0.3IU/L;20个健康体检者血清TRAb检测结果仅1个超出参考区间≤1.9IU/L;与Roche ECLIA的诊断总符合率90%,阳性符合率75%,阴性符合率100%,Kappa检验值0.7826(P<0.001)。结论 迈瑞高敏磁微粒CLIA的精密度、基于患者血清的正确度、线性范围、检出限均符合厂家声明,参考区间经验证可转移至我实验室...     

基蛋生物肌酸激酶同工酶项目性能验证

目的评价基蛋生物Getein1600荧光免疫定量分析仪分析CK-MB的正确度、精密度、线性范围,为POCT的应用提供质量保证。方法参考美国临床与实验室标准化协会(CLSI)EP9-A2文件对基蛋生物Getein1600荧光免疫定量分析仪与雅培I2000全自动免疫分析仪进行方法学比对,验证正确度;采用EP15-A进行精密度验证;采用EP6-A对线性范围进行验证。结果CK-MB在两台仪器的比对结果相关性良好(R=0.9936,P>0.05);CK-MB均值为4.58、10.47、14.99时总CV分别为8.75%、9.29%、6.45%。CK-MB项目线性范围参考品理论值与测试平均值回归系数R2=0.990,在3.06~72.51ng/mL浓度区间呈线性,该分析测量范围通过验证。结论基蛋生物Getein1600荧光免疫定量分析仪性能验证良好,与厂家说明书声明相符。     

全自动生化分析仪检测肌酸激酶同工酶质量分析性能验证

目的验证全自动生化分析仪定量检测系统检测肌酸激酶同工酶质量(CKMB mass)的分析性能,确保检验结果的准确。方法参照CLSI系列相关文件、国家相关卫生行业标准、并结合实际情况,对定量检测系统的精密度、正确度、线性范围、临床可报告范围、生物参考区间等分析性能进行验证、评价,将实验室验证结果与质量允许范围进行比较;并对CKMB/CK活性升高或倒置现象进行验证。结果贝克曼AU5400全自动生化分析仪测定CKMB mass浓度在14.185、36.467 ng/mL时,实验室批内不精密度(CVr)分别为2.778%、2.172%,总不精密度(CVl)分别为4.507%、2.255%;与罗氏E602全自动电化学发光分析仪测定CKMB mass进行患者样本比对,回归方程Y=1.0277 X-0.5778,R2=0.9846,相关性良好,5、10、15、90 ng/mL浓度水平处的预期偏倚分别为-8.8%、-3.0%、-1.1%、2.1%,可接受;线性范围为1.865~186.34 ng/mL;临床可报告范围为1.865~1490.72 ng/mL;生物参考区间0~5 ng/mL适用于本实验室;能够很好的纠正实验室CKMB/CK活性假性升高或倒置的现象。结论贝克曼AU5400全自动生化分析仪测定CKMB mass的精密度、正确度、线性范围、临床可报告范围、参考区间等性能良好,能够规范检测、确保检测质量,满足临床需求。     

尿微量白蛋白检测试剂盒性能评价

目的评价北京九强生物免疫比浊法尿微量白蛋白检测试剂盒的性能。方法评价九强生物免疫比浊法检测尿微量白蛋白的精密度、准确度、线性范围、最大稀释倍数、前带性能以及特异性。结果精密度实验显示,日内不精密度高低浓度质控的变异系数(CV)分别为0.61%和0.70%,日间精密度高低浓度质控的CV分别为1.95%和2.83%;准确度实验结果显示,九强生物与罗氏尿微量白蛋白检测试剂盒的检测结果回归方程为Y=1.0169X+5.7251,相关系数(r)为0.9987;测量线性范围与厂家提供的范围一致;最大稀释倍数最大可达40倍;检测样本浓度43000mg/L时前带样本仍在可控范围;在厂家说明书标示的干扰物浓度范围内,对检测结果没有明显影响。结论九强生物的mALB检测试剂盒精密度好、准确度高、线性范围宽、前带性能好,性能完全能满足临床的使用要求。     

ARCHETECT高敏肌钙蛋白Ⅰ试剂盒性能评价

目的 评价ARCHETECT高敏肌钙蛋白Ⅰ（hs-cTnⅠ）试剂盒性能,以验证其是否符合临床实验室使用要求。方法 参考CLSI的EP15-A2文件和相关文献对ARCHETECT高敏肌钙蛋白Ⅰ试剂盒精密度、正确度进行评价,EP17-A文件和相关文献对空白检测限（LoB）进行评价,EP6-A文件和相关文献对线性范围进行评价,参考NCCLS C28-A2文件,对健康体检者血浆标本分男女验证生物参考区间。结果 实验测得hs-cTnⅠ高值样本（5.702 μg/L）的批内不精密度CV为1.56%,总不精密度CV为1.27%,低值样本（0.003 μg/L）的批内不精密度CV和总的不精密度CV均为0;hs-cTnI的回收率为 97.50%;LoB为0.001 μg/L;在检测范围内,hs-cTnI理论值与测定值的线性方程为Y=1.0006X-0.13136,R2=0.9999;生物参考区间验证结果显示男性100.00%的结果在厂家提供的生物参考区间范围内,女性96.67%的结果在厂家提供的生物参考区间范围内。结论 ARCHETECT高敏肌钙蛋白Ⅰ试剂盒性能通过验证,可为临床提供准确、可靠的hs-cTnⅠ定量检测结果,为临床对心肌损伤的诊断、治疗提供重要信息。     

化学发光微粒子免疫法检测鳞状上皮细胞癌抗原的方法学评价

目的 对化学发光微粒子免疫法检测鳞状上皮细胞癌抗原(SCC Ag)进行方法学评价及性能验证.方法 对化学发光微粒子免疫法检测鳞状上皮细胞癌抗原的不精密度、回收率、线性分析、定量可报告低限值、特异性和灵敏度、反复冻融试验以及参考范围验证等方面进行评价.结果 化学发光微粒子免疫法检测鳞状上皮细胞癌抗原低、中、高值样本批内不精密度CV％分别为3.88％、2.80％和0.69％,批间不精密度CV％分别为3.98％、3.10％和3.17％;回收率为95.77％～102.25％,平均回收率为98.89％;线性分析R2为0.9997;定量可报告低限值为0.21ng/mL,CV％为15.06％;特异性为96％,灵敏度为94％;低、中、高值样本反复冻融试验CV％分别为7.99％、2.97％和1.36％;参考范围验证的检测结果均＜1.3ng/mL.结论 化学发光微粒子免疫法检测鳞状上皮细胞癌抗原方法符合实验室要求,检测性能良好,可广泛在实验室开展应用.     

The universal muscular chamber. A basic unit of the genitourinary, cardiovascular, gastro-intestinal, skeletal, cutaneous, respiratory and other systems, endocameral hypertension; and spasm, the key to their idiopathic diseases and arthropathies

Starting with the integument, we see many organs are contractile sacs or multiples thereof, which tubes or bags constitute the major part of the entire body. Recognition of this basic unit and its characteristics sheds new light, individually and collectively, on many disorders previously considered unrelated. Muscular tears and perforations develop in the walls of these chambers, being no way peculiar to those organs, wherein, hydrochloric acid occurs. So, it is not necessary to explain the absence of excessive acid from patients who exhibit holes in the gastric, uterine, aortic, duodenal, rectal, pulmonary, retina, and other walls. Muscle, not acid is the great common factor relating idiopathic disorders in the gastrointestinal tract to each other and to similar diseases in other systems. When the units are linked together, the lesions tend to appear as arthropathies, i.e. at the joints. Rephrasing common-place observations, frees us from conventional, conceptual cul-de-sacs. An observation is only as good as its interpretation, so all possibilities must be considered, otherwise, we will remain blinded by our misconceptions.     

Longitudinal study on trace mineral compositions (selenium, zinc, copper, manganese) in Korean human preterm milk

We measured selenium, zinc, copper and manganese concentrations in the human milk of Korean mothers who gave birth to preterm infants, and compared these measurements with the recommended daily intakes. The samples of human milk were collected postpartum at week-1, -2, -4, -6, -8, and -12, from 67 mothers who gave birth to preterm infants (< 34 weeks, or birth weight < 1.8 kg). All samples were analyzed using atomic absorption spectrophotometry. The concentrations of selenium were 11.8 ± 0.5, 11.4 ± 0.8, 12.7 ± 0.9, 11.4 ± 0.8, 10.8 ± 0.9, and 10.5 ± 1.3 μg/L, zinc were 7.8 ± 0.5, 9.1 ± 0.8, 7.2 ± 0.9, 8.0 ± 0.8, 7.4 ± 0.9, and 6.6 ± 1.2 mg/L, copper were 506 ± 23.6, 489 ± 29.4, 384 ± 33.6, 356 ± 32.9, 303 ± 35.0, and 301 ± 48.0 μg/L and manganese were 133 ± 4.0, 127 ± 6.0, 125 ± 6.0, 123 ± 6.0, 127 ± 6.0, and 108 ± 9.0 μg/L at week-1, -2, -4, -6, -8, and -12, respectively. The concentrations of selenium and zinc meet the daily requirements but that of copper is low and of manganese exceeds daily requirements recommended by the American Academy of Pediatrics, Committee on Nutrition.     

Correction of cardiotoxic effects of cardiac antiarrhythmics with befol, suphan, and their combinations

Antidepressant befol, non-glycoside cardiotonic suphan, and their combinations were shown to have different ability to decrease cardiotoxic (arrhythmogenic) effect of novocainamide, lidocaine, bonnecor, obsidan, cordarone, verapamil, and rhythmidazol. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 125, No. 6, pp. 641–646, June, 1998     

Antiarrhythmic activity of befol, suphan, mexidol, and T3-146 in combination with some antiarrhythmics

Antidepressant befol, nonglycoside cardiotonic suphan, succinate-containing synthetic antioxidant mexidol, and pyracetam structural analogue T3-146 were shown to possess antiarrhythmic activity and to potentiate antiarrhythmic effects of bonnecore, obsidan, amiodarone, isoptin, and richlocaine. Translated fromByulleten' Eksperimental'noi Biologii I Meditsiny, Vol. 125, No. 5, pp. 544–547, May, 1998     

HLA genes in Macedonians and the sub-Saharan origin of the Greeks

HLA alleles have been determined in individuals from the Republic of Macedonia by DNA typing and sequencing. HLA-A, -B, -DR, -DQ allele frequencies and extended haplotypes have been for the first time determined and the results compared to those of other Mediterraneans, particularly with their neighbouring Greeks. Genetic distances, neighbor-joining dendrograms and correspondence analysis have been performed. The following conclusions have been reached: 1) Macedonians belong to the "older" Mediterranean substratum, like Iberians (including Basques), North Africans, Italians, French, Cretans, Jews, Lebanese, Turks (Anatolians), Armenians and Iranians, 2) Macedonians are not related with geographically close Greeks, who do not belong to the "older" Mediterranenan substratum, 3) Greeks are found to have a substantial relatedness to sub-Saharan (Ethiopian) people, which separate them from other Mediterranean groups. Both Greeks and Ethiopians share quasi-specific DRB1 alleles, such as *0305, *0307, *0411, *0413, *0416, *0417, *0420, *1110, *1112, *1304 and *1310. Genetic distances are closer between Greeks and Ethiopian/sub-Saharan groups than to any other Mediterranean group and finally Greeks cluster with Ethiopians/sub-Saharans in both neighbour joining dendrograms and correspondence analyses. The time period when these relationships might have occurred was ancient but uncertain and might be related to the displacement of Egyptian-Ethiopian people living in pharaonic Egypt.     

Voluntary consumption of NaCl,KCl, CaCl2, and NH4Cl solutions by 28 mouse strains

Male mice from 28 inbred strains (129P3/J, A/J, AKR/J, BALB/cByJ, BUB/BnJ, C3H/HeJ, C57BL/6J, C57L/J, CAST/Ei, CBA/J, CE/J, DBA/2J, FVB/NJ, I/LnJ, KK/H1J, LP/J, NOD/LtJ, NZB/B1NJ, P/J, PL/J, RBF/DnJ, RF/J, RIIIS/J, SEA/GnJ, SJL/J, SM/J, SPRET/Ei, and SWR/J) were tested with NaCl (75–450 mM), KCl (30–300 mM), CaCl₂ (3–100 mM), and NH4Cl (10–300 mM) solutions using two-bottle preference tests with water as the second choice. For each mineral, there was a wide range of strain variation in solution intakes and preferences. This variation had a substantial genetic component as assessed using heritability estimates. In most cases, the strain means were continuously distributed; however, strains with deviating high or low intakes or preferences were also observed. The associations among the responses to different minerals were only modest, suggesting distinct genetic controls of sodium, potassium, calcium, and ammonium consumption. These results provide a valuable resource for investigators who wish to identify genes involved in the regulation of mineral consumption and balance.     

Primary cutaneous neuroendocrine tumor (atypical carcinoid) expressing KIT and PDGFRA with myoepithelial differentiation: a case report with immunohistochemical and molecular genetic studies

Primary cutaneous neuroendocrine tumors (NET) except for Merkel cell carcinoma have rarely been reported. Herein reported is a very unique case of primary cutaneous NET with immunohistochemical markers of myoepitheliomas. A 47-year-old woman presented a tumor measuring 0.8x0.9x0.6 cm of the face. The tumor was excised completely with wide margins. Morphologically, the tumor was located in the dermis, and the tumor was composed of epithelioid cells arranged in trabecular, sinusoidal, rosette, ribbon-like, and cord-like patterns. Focal areas show tubular formations. The tumor cells were homogenous, and their nuclei showed hyperchromasia but no apparent histological features of malignancy were seen. The stroma was very scant. No invasive features were seen. Immunohistochemically, the tumor cells were strongly positive for cytokeratin (CK) 34BE12, CD5/6, CK14, NCAM (CD56), p63, and KIT (CD117), and moderately positive for CK AE1/3, p53, chromogranin, synaptophysin, neuron-specific enolase (NSE), PDGFRA, CA19-9, and Ki-67 antigen (labeling index=23%). The tumor cells were negative for CK CAM5.2, CK7, CK8, CK18,CK19,CK20, EMA, vimentin, CEA, HMB45, S100 protein, α-smooth muscle antigen, desmin, CD34, GFAP, neurofilaments, CD99 (MIC2), CD45, CD57, ErbB2, TTF-1, MUC1, MUC2, MUC5AC, and MUC6. Mucins examined by d-PAS and Alcian blue techniques were negative. A genetic analysis using PCR-direct sequencing method in paraffin sections identified no mutations of KIT (exons 9, 11, 13 and 17) and PDGFRA (exons 12 and 18) genes. Imaging modalities including CT and MRI identified no tumor in the body. The clinicians thought that the tumor was cured. She was a sailor and immediately visited other countries; therefore the follow-up could not be done.     

Neonatal syncytial giant cell hepatitis with paramyxoviral-like inclusions

Syncytial giant cell hepatitis in the neonatal period has been associated with many different etiologic agents and may present initially as cholestasis. Infectious causes are most common and include: (1) generalized bacterial sepsis, (2) viral agents, (3) toxoplasmosis, (4) syphilis, (5) listeriosis, and (6) tuberculosis. Viral hepatitis may be due to cytomegalovirus, rubella virus, herpes simplex, HHV-6, varicella, coxsackievirus, echovirus, reovirus 3, parvovirus B19, HIV, enteroviruses, paramyxovirus, and hepatitis A, B, or C (rare). Giant cell hepatitis may result in fulminant liver failure with massive hepatocyte necrosis and severe liver dysfunction leading to death, resolution with severely compromised liver function, or liver transplantation. The authors report a 6-week-old male who had an unremarkable perinatal period, became jaundiced after developing diarrhea, and subsequently developed liver dysfunction with massively increased liver enzymes and a coagulopathy. Open wedge and core liver biopsies were performed to determine if the patient should be listed for liver transplantation. Giant cell hepatitis with a significant mixed lymphocytic and neutrophilic infiltrate was present on both the wedge and core biopsies. The residual 60% of hepatocytes had ballooning degeneration and many possessed pyknotic nuclei. The hepatocytes were arranged in a pseudoacinar pattern. Electron microscopy showed paramyxoviral-like inclusions in the giant cells, characterized as large inclusions with fine filamentous, beaded substructures (18-20 nm). Paramyxoviridae are nonsegmented, negative-sense, single-stranded RNA viruses. This family is divided into the Paramyxovirinae subfamily containing respirovirus (Sendai virus, parainfluenza virus type 3), rubula virus (mumps, parainfluenza virus type 2), and morbillivirus genera (measles); and Pneumovirinae subfamily (pneumovirus genus [respiratory syncytial virus]). Supportive care to determine if hepatic function resolves following the viral episode, liver transplantation with fulminant liver failure, and ongoing evaluation in those who recover to assess chronic liver disease are necessary. Ultrastructural evaluation may unmask the etiologic agent for hepatitis and direct therapy.     

Mitochondrial dysfunction and molecular pathways of disease

Since the first mitochondrial dysfunction was described in the 1960s, the medicine has advanced in its understanding the role mitochondria play in health, disease, and aging. A wide range of seemingly unrelated disorders, such as schizophrenia, bipolar disease, dementia, Alzheimer's disease, epilepsy, migraine headaches, strokes, neuropathic pain, Parkinson's disease, ataxia, transient ischemic attack, cardiomyopathy, coronary artery disease, chronic fatigue syndrome, fibromyalgia, retinitis pigmentosa, diabetes, hepatitis C, and primary biliary cirrhosis, have underlying pathophysiological mechanisms in common, namely reactive oxygen species (ROS) production, the accumulation of mitochondrial DNA (mtDNA) damage, resulting in mitochondrial dysfunction. Antioxidant therapies hold promise for improving mitochondrial performance. Physicians seeking systematic treatments for their patients might consider testing urinary organic acids to determine how best to treat them. If in the next 50 years advances in mitochondrial treatments match the immense increase in knowledge about mitochondrial function that has occurred in the last 50 years, mitochondrial diseases and dysfunction will largely be a medical triumph.     

Preferences of 14 rat strains for 17 taste compounds

Two-bottle choice tests were used to assess the taste preferences of 8 male and 8 female rats from 3 outbred strains (SD, LE, WI) and 11 inbred strains (BN, BUF, COP, DA, Dahl-S, F344, FHH, LEW, Noble, PVG, SHR). Each rat received a series of 109 48-h tests with a choice between water and a “taste solution”. Four to eight concentrations of the following compounds were tested: NaCl, CaCl₂, NH₄Cl, KCl, MgCl₂, saccharin, sucrose, ethanol, HCl, citric acid, quinine hydrochloride (QHCl), caffeine, denatonium, monosodium glutamate (MSG), Polycose, corn oil, and capsaicin. Strain differences (p < 0.001) were observed in preferences for at least one concentration of all compounds tested except denatonium (p = 0.0015). There were also strain differences in the following ancillary measures: fungiform papillae number, water intake, food intake, and body weight. There were sex differences in food intake and body weight but no concerted sex differences in any of the other measures, including preferences for any taste solution. This comprehensive source of information can be used to guide the choice of appropriate rat strains and taste solution concentrations for future genetic studies.