Microarray technology: the future of blood testing?

The increasing pace of development in molecular biological techniques during the last 10-15 years has had a direct effect on mass testing and diagnostic applications, including blood screening. Nucleic acid amplification techniques (NAT), usually based on the polymerase chain reaction (PCR), have been successfully applied to blood grouping and implemented recently in screening of blood donations for hepatitis C virus (HCV). The majority of microarray technologies involve an amplification step, yet the main benefits of this technology come from simultaneous analysis of thousands of analytes. Microarrays were developed to utilize the huge amount of information provided by genome projects, but they have clear potential in mass screening and diagnostics. The application of microarray technology may revolutionize blood testing, providing for the first time the prospect of an integrated platform for comprehensive donor and donation testing, replacing multiple individual assays. Design features of a blood-testing chip and various technologies with potential application in this field are discussed in this review.     

Significance of ‘recovery ST-segment depression’ in exercise stress test

ObjectiveTo study the significance of ST-segment depression during ‘recovery’ compared to that ‘during stress’ and ‘both the phases’ in exercise stress test.MethodsPatients with positive exercise stress test who underwent coronary angiography (CAG) from 1st January 2017 to 31st December 2018 were studied. Patients were divided into 3 groups- Group A with ST-depression restricted to recovery phase, group B with ST-depression restricted to stress phase and group C with ST-depression seen both during exercise and recovery. All patients underwent CAG. Sensitivity, specificity, and predictive values of each of these groups in diagnosis of significant coronary artery disease (CAD) were analysed and compared.ResultsTotal 300 patients were studied. Mean age of the study population was 48.77 ± 7.94 years. 78.3% of patients with positive exercise stress test had significant CAD. 96% of patients in group A had significant CAD, which was higher than in group B (88.9%) & group C (70.1%). The specificity, positive predictive value and negative predictive value of ST-segment depression in group A (96.92%, 96% and 25.2% respectively) were higher than that of ST-depression in group B (89.23%, 88.89% and 24.47% respectively) and group C (13.85%, 70.05% and 7.96% respectively). Sensitivity and accuracy of ST-depression in group A were lower (20.43% and 37% respectively), compared to other 2 groups.ConclusionPatient with ST-depression restricted to recovery phase had highest specificity, positive predictive value, and negative predictive value. However, accuracy was highest in group with both stress phase and exercise ST-segment depression.     

Can pre-treatment with beta-agonists reduce stress test time and the use of atropine in dobutamine stress testing?

AIM: To determine whether the use of inhaled beta-agonists decreases the duration of dobutamine stress testing (DAS), reduces the amount of dobutamine infused and decreases the use of atropine. METHODS: 34 patients on beta-agonists (group A) (mean age 65 +/- 8 years) and 32 patients not on beta-agonists or beta-blockers (group B) (mean age 65 +/- 10 years) undergoing DAS with SPECT were enrolled. RESULTS: The time of infusion of dobutamine in group A was 6.41 +/- 1.58 min and in group B was 9.77 +/- 3.60 min (p < 0.001). The amount of dobutamine infused was 10.64 +/- 5 mg in group A and 19.20 +/- 8 mg in group B (p < 0.001). In group A, 2 of 34 patients and 18 of 32 patients in group B needed atropine to reach peak HR (p < 0.001). CONCLUSION: Patients on short acting beta-agonists require smaller amounts of dobutamine with a shorter infusion time during DAS, and lesser use of side-effect prone atropine.     

Does the 6‐min walk test correlate with the exercise stress test in children?

Is there a correlation between the 6‐min walk and aerobic fitness in children? We studied healthy and cystic fibrosis (CF) subjects age 8–20 years using the 6‐min walk test, treadmill graded exercise stress test, and spirometry. Six‐minute walk distance (6MWD) and the product of 6MWD and body weight (6MWORK) were related to aerobic capacity. Data were analyzed using Student's t‐test and Pearson correlation. 13 healthy subjects [9 females, mean age 15.8 ± 3.6 years, % predicted forced expiratory volume in one second (FEV₁) 105 ± 12%, 6MWD 557 ± 73 m, peak oxygen uptake ( max) 41.4 ± 7.2 ml/kg/min, and heart rate (HR) at max 180 ± 10] and 11 CF subjects (3 females, mean age 14.3 ± 3.8 years, FEV₁ 67 ± 25.9%, 6MWD 468 ± 68 m, max 27.0 ± 8.1 ml/kg, and HR at max 163 ± 22] were studied. 6MWD correlates with max in normal subjects (r = 0.59, P < 0.05) but not in CF subjects (r = 0.09, NS). 6MWORK correlates with max in CF subjects (r = 0.65, P < 0.05) but not in normal subjects (r = 0.278, NS). We conclude that the 6MWD corresponds with aerobic fitness in normal pediatric subjects and 6MWORK corresponds with aerobic fitness in CF subjects. We speculate that 6MWORK is superior to 6MWD for assessment of aerobic fitness in children with CF. Pediatr Pulmonol. 2010; 45:135–140. © 2010 Wiley‐Liss, Inc.     

Cardiopulmonary exercise testing in patients with moderate-severe obesity: a clinical evaluation tool for OSA?

Sleep and Breathing - Obstructive sleep apnea (OSA) is a widespread comorbidity of obesity. Nasal continuous positive airway pressure (CPAP) has been demonstrated very effective in treating...     

Can measurement of the intima-media thickness of the carotid artery improve the diagnostic value of exercise stress tests?

OBJECTIVE: The diagnostic value of the exercise electrocardiogram (ECG) for the detection of coronary artery disease is hampered by a high proportion of equivocal results, especially in asymptomatic patients. The intima-media thickness of the carotid artery correlates well with the degree of atherosclerosis, also in other vascular beds, such as the coronary arteries. The aim of this study is to evaluate whether measurements of intima-media thickness can improve the diagnostic value of stress ECG in the detection of coronary artery disease. METHODS: Patients without a history of vascular disease and with equivocal exercise stress ECG results were included. The intima-media thickness was measured with high resolution echography at the posterior wall of the common carotid artery, using an automated edge-tracking method. The diagnosis of coronary artery disease was based on the presence of reversible perfusion defects on exercise MIBI-scintigrams. RESULTS: A total of 90 patients (46 men, 44 women) with a mean age of 53.7 years were included. The MIBI-scintigraphy was positive in 17. There was no difference in mean intima-media thickness between MIBI positive and MIBI negative patients (635.76 +/- 84.56 microm and 643.89 +/- 107.06 microm, respectively, p = 0.8). Using multiple regression analysis, neither intima-media thickness measurements, nor classic risk factors could predict the result of MIBI-scintigraphy. Intima-media thickness was mainly influenced by age and hypertension. CONCLUSIONS: In this study, neither intima-media thickness measurements, nor classic risk factors could improve the diagnostic value of stress ECG in the detection of coronary artery disease. In case of equivocal stress results, additional cardiovascular imaging techniques remain recommended.     

Slow upsloping ST-segment depression during exercise: does it really signify a positive stress test?

Background Slow upsloping ST-segment depression during stress is thought to represent an ischemic response to exercise treadmill testing (ETT). Aim We used modern single-photon emission computed tomography (SPECT) imaging protocols to determine the incidence of ischemia in patients with slow upsloping ST depression during exercise and whether this response signifies more or less severe coronary artery disease (CAD) and risk in comparison with rapid upsloping ST depression and particularly with horizontal or downsloping ST depression. Methods We enrolled 33 patients (group 1) with rapid upsloping ST depression (>1 mm extending <0.08 seconds beyond J point), 32 patients (group 2) with slow upsloping depression (>1.5 mm extending >0.08 seconds beyond J point), and 35 patients (group 3) with horizontal or downsloping depression (>1 mm at 0.08 seconds beyond J point). Summed stress score (SSS), summed difference score (SDS), stress extent percent (SE%) and reversible extent percent (RE%) of perfusion abnormalities, lung-heart ratio (LHR), and transient ischemic dilatation (TID) were calculated. Results The mean SSS, SDS, SE%, RE%, and LHR were similar between groups 1 and 2 but significantly higher in group 3. Incidence of ischemia was similar in groups 1 and 2 (39% and 25%) but significantly higher in group 3 (77%, P < .001). Evidence of TID was seen in none of the patients in groups 1, in 3% of patients in group 2, and in 23% of patients in group 3. Conclusions Slow upsloping ST depression does not signify more severe ischemia, more extensive CAD, or more stress-induced backward left ventricular failure. Thus, it would be reasonable to consider patients with slow upsloping ST depression during exercise as having a very low likelihood of CAD, similar to patients with rapid upsloping ST depression. (Am Heart J 2002;143:482-7.)     

Exercise capacity in adult African-Americans referred for exercise stress testing: is fitness affected by race?

STUDY OBJECTIVES: To determine the factors associated with exercise capacity. DESIGN: Retrospective evaluation of large stress-testing database. SETTING: Multispecialty tertiary care center. PATIENTS: A total of 5,069 consecutive patients who were referred for exercise stress testing. MEASUREMENTS: We compared levels of fitness in 641 African-Americans (52% male) with 4,428 whites (73% male), and performed univariate and multivariate analyses to determine the predictors of fitness (including race). RESULTS: Compared with African-American men (mean [+/- SD] age, 60 +/- 11 years), white men (mean age, 63 +/- 11 years) have significantly higher exercise capacity (10.7 +/- 3.5 vs 11.4 +/- 3.4 metabolic equivalents [METs], respectively; p < 0.001). The exercise capacity in African-American and white women was similar (8.5 +/- 2.9 vs 8.7 +/- 3.0 METs, respectively). However, body mass indexes (BMIs) were significantly higher in both African-American men (29.1 +/- 4.3 vs 28.2 +/- 4.3 kg/m(2), respectively; p < 0.001) and women (30.2 +/- 5.7 vs 27.9 +/- 5.5 kg/m(2), respectively; p < 0.0001) compared to their white counterparts, as was the prevalence of obesity (men, 44% vs 33%, respectively; women, 37% vs 27%, respectively; both p < 0.001). Although a model containing age, gender, BMI, and race only accounted for 32% of exercise capacity, all independently (p < 0.0001) predicted higher exercise capacity, as follows: younger age (r(2) = 0.14); male gender (r(2) = 0.12); BMI (r(2) = 0.06); and white race (r(2) = 0.004). CONCLUSIONS: In an adult population of individuals who were referred for exercise stress testing, African-Americans were more obese and had significantly lower exercise capacity than their white counterparts. Emphasis on weight reduction and increasing physical fitness is particularly needed for the prevention of cardiovascular diseases in African-Americans.     

Is rest or exercise hypertension a cause of a false-positive exercise test?

STUDY OBJECTIVES: To determine if a history of hypertension or an exaggerated rise in exercise systolic BP is associated with a false-positive exercise ECG. DESIGN, SETTING, AND PATIENTS: Retrospective analysis of the associations between exercise-induced ST-segment depression and a history of hypertension, exercise systolic BP, and several other clinical and exercise test variables. Among 20,097 patients referred for exercise tomographic thallium imaging in a nuclear cardiology laboratory at a tertiary care center, 1,873 patients met inclusion criteria for this study, which included no history of myocardial infarction or coronary artery revascularization, a normal resting ECG, and normal exercise thallium images. RESULTS: False-positive ST-segment depression occurred in 20% of the population. A history of hypertension was actually associated with a lower likelihood of ST-segment depression (odds ratio, 0.70; 95% confidence interval [CI], 0.55 to 0.89; p = 0. 004). A higher peak exercise systolic BP was associated with a higher likelihood of ST-segment depression (odds ratio, 1.08 for each 10-mm Hg increase in systolic BP; 95% CI, 1.03 to 1.14; p < 0. 001). However, the association between peak exercise systolic BP and ST-segment depression was so weak that this measurement could not be predictive in the individual patient (R(2) = 0.2%). For every 20-mm Hg increase in peak exercise systolic BP, the percentage of patients with ST-segment depression increased by only 3%. CONCLUSIONS: In patients with normal resting ECGs, we conclude the following: (1) a history of hypertension is not a cause of a false-positive exercise test, and (2) higher exercise systolic BP is a significant but weak predictor of ST-segment depression.