The relationship between serum concentration of cardiac troponin I in chronic renal failure patients and cardiovascular events.

OBJECTIVE: The purpose of this study was to evaluate the relationship between serum cardiac troponin I in asymptomatic chronic renal failure patients and cardiovascular events. BACKGROUND: Short-term follow-up studies on this subject produced conflicting results. MATERIAL AND METHOD: A total of 63 asymptomatic patients with chronic renal failure (CRF) with regular hemodialysis were followed for 18 months for cardiac mortality, myocardial infarction events and interventional procedures such as percutaneous transluminal coronary angioplasty (PTCA) and coronary artery bypass graft (CABG). Serum cTnI and other blood chemistries were measured at the time of the study. RESULTS: Forty seven chronic dialysis patients (75%) had an elevated level of cTnI concentration more than the 0.08 ng/ml cutoff but only fourteen patients (22%) had and elevated cTnI concentration of more than the AMI cutoff (0.4ng/ml). When using the 0.08 ng/ml cutoff, the NT-proBNP concentrations of the elevated groups were significantly higher than the normal groups. The authors also found that the elevated groups above the AMI cutoff had significantly higher cardiovascular events. CONCLUSION: Elevated cTnI concentrations are commonly found in chronic renal failure patients. The AMI cutoff level of cTnI (0.4 ng/ml) seem to have a benefit for predicting the cardiovascular events in asymptomatic chronic renal failure patients while the 0.08 ng/ml cutoff doesn't have usefulness for this purpose. Further studies are needed to clarify this hypothesis.

Serum lipoprotein (a) level and restenosis after percutaneous coronary intervention.

Restenosis is regarded as the result of a combination of various pathological events. The mechanisms are complex and not completely understood. In this study, the authors focused on the lipoprotein (a) (Lp (a)). It is one of the novel risk factors in atherosclerotic vascular disease. Numerous clinical studies suggest that individuals with elevated blood levels of Lp (a) have been shown to be associated with atherosclerotic vascular disease. However, whether a high serum concentration of Lp (a) affects restenosis after PCI remains controversial. In this study, the relationship between serum Lp (a) levels and restenosis after PCI was examined to investigate whether serum Lp (a) levels may be a predictor of restenosis after PCI. Of the 100 patients studied, 31 patients (31%) were classified as the restenosis group and 69 patients (69%) the non-restenosis group. Both groups did not significantly differ in serum concentration of total cholesterol, triglyceride, HDL-C, and LDL-C. The mean serum Lp (a) concentration in patients with restenosis was 41.50 +/- 34.99 mg/dL compared with a mean serum Lp (a) concentration of 29.87 +/- 25.47 mg/dL in those without restenosis. There was no statistical significance of Lp (a) level between the restenosis and non-restenosis groups (p=0.06). In healthy subjects, the normal reference range of serum Lp (a) concentration is below 30 mg/dL. From this reference, if a cut off point of serum Lp (a) concentration equal to 30 mg/dL or above to identify high Lp (a) level group was used. High serum Lp (a) level was established in 15 patients with restenosis versus 21 patients without restenosis. From this cut off point of serum Lp (a) level, the authors did not find a correlation between serum Lp (a) level and the restenosis group. (p=0.08).

Rapid detection of Chlamydia pneumoniae DNA in peripheral blood mononuclear cells of coronary artery disease patients by real-time fluorescence PCR.

Several recent reports including serological, pathological and animal studies have associated Chlamydia pneumoniae with coronary artery disease (CAD). In order to establish whether chronic C. pneumoniae infection is linked to coronary artery disease, clinical intervention trials may be needed. However, to detect eligible patients with persistent infection, a reliable diagnostic marker must be developed for identifying cases and assessing efficacy of antichlamydial therapy. Moreover, the prevalence of circulating C. pneumoniae DNA in CAD patients varied widely from previous reports. A real-time PCR has been established by using HL-1 and HR-1 primer to amplify 437 base pairs product. Confirmation of the product was performed on LightCycler by melting curve analysis of detection probes labeled with LC-Red705. Ninety-five angiographically confirmed CAD patients and 104 normal, healthy volunteers were recruited. The mononuclear cell layer was separated from collected blood and rapid, single step real-time PCR was used to detect C. pneumoniae DNA. C. pneumoniae DNA in peripheral blood mononuclear cells (PBMC) was found in 17 per cent of 95 CAD patients and 1 per cent of 104 normal healthy volunteers (odds ratio 20.86, 95% confidence interval 2.71 - 160.67, p < 0.0001). There was no association between C. pneumoniae DNA in PBMC and serological status. The rapid, real-time PCR showed a clear-cut result between positive and negative cases. PBMC-based real-time PCR may be a useful tool for identifying subjects carrying C. pneumoniae in the circulation or in the vascular wall as well. It will be a specific indicator of current infection and will be used as a marker for assessing the microbiological efficacy of antichlamydial therapy in clinical intervention trials.

Prevalence of hyperhomocysteinemia in normal healthy Thai subjects.

The concentration of circulating total homocysteine is a sensitive marker of inadequate folate and vitamin B12 status. The elevations of plasma homocysteine concentration are associated with an increased risk of vascular disease. The primary goals of this study were to identify plasma homocysteine concentrations in Thai residents and to test for differences in homocysteine levels among sex and age categories. The authors measured plasma total homocysteine concentrations in 3,345 Shinawatra employees (1,133 males, 2,212 females aged between 20-65 years) by using fluorescence polarization immunoassay (FPIA) method. The mean plasma homocysteine concentrations of males and females were 11.495 and 8.547 micromol/L respectively. Plasma homocysteine concentrations were significantly lower in females than in males (p < 0.0001). The age-specific plasma homocysteine levels were lower in females than in males for each group, but the levels of each group was not significantly different both in males and females. When more than 12 micromol/L was used as the cut-off value, it was found that 33.6 per cent of males and 6.69 per cent of females were classified as hyperhomocysteinemia subjects. The authors concluded that the prevalence of hyperhomocysteinemia in Thai males is more common than in females. Further investigation should be done to clarify the association between serum folate, vitamin B12, vitamin B6 concentrations and plasma homocysteine concentration.

Homocysteine and restenosis after percutaneous coronary intervention.

Numerous clinical studies in Western and Asian countries suggest that individuals with elevated blood levels of homocysteine have an increased risk of atherosclerosis, myocardial infarction, cerebral infarction, and deep vein thrombosis. Homocysteine is also known to induce both atherogenic and thrombogenic mediators in cultured vascular cells so that homocysteine may influence the damage of endothelial cells, promote smooth muscle cell growth, induce atherogenic mediators and thrombus formation after coronary angioplasty. The association between homocysteine and restenosis after percutaneous coronary intervention (PCI) has been discussed. In this study, the relationship between plasma homocysteine levels and restenosis after PCI to investigate whether plasma homocysteine levels may be a predictor of restenosis after PCI was examined. One hundred consecutive patients who underwent successful PCI were enrolled and plasma homocysteine level was measured in all patients prior to PCI. Plasma for homocysteine level was obtained in 99 of 100 patients who had angioplasty. The mean plasma homocysteine concentration in the enrolled patients was 13.61 +/- 6.04 micromol/L. The minimum and maximum of plasma homocysteine were 4.40 micromol/L and 50.00 micromol/L, respectively. In healthy subjects, the normal reference range of homocysteine level is 5-15 micromol/L However, recent data suggest that some patients may be at increased cardiovascular and cerebrovascular risk at levels as low as 12 micromol/L. For this reason, both cut off points of homocysteine level > or = 15 micromol/L or > or = 12 micromol/L to identify the high homocysteine level group were used. Of 99 patients, high homocysteine level (> or = 15 micromol/L) was established in 9 patients with restenosis versus 20 patients without restenosis. If the cut off point of homocysteine level > or = 12 micromol/L was used, high homocysteine level was established in 14 patients with restenosis versus 39 patients without restenosis. From both cut off points of homocysteine level, there was no correlation between plasma homocysteine level and the restenosis group. (p>0.05).

Serum magnesium in Thai coronary artery disease patients.

Hypomagnesemia or magnesium (Mg) deficiency has been hypothesized to play a role in coronary artery disease (CAD). The authors aimed to evaluate serum Mg concentration in 100 CAD patients compared with 100 healthy controls. Mean values of serum Mg level in CAD and the control group were 2.14 +/- 0.39, 2.24 +/- 0.3 mg/dL respectively (P=0.052). The prevalence of Mg deficiency was 12 per cent in the CAD patients, and 5 per cent in the control group (odds ratio=2.59, 95% confident interval = 0.88-7.65, P=0.063). There was no significant difference in the serum Mg level between the 2 groups, although it tended to be lower in CAD patients. The prevalence of Mg deficiency did not differ significantly between the study group, however, it tended to be higher in CAD patients. These findings demonstrated that CAD patients may be associated with Mg deficiency, and contribute to the pathogenesis of CAD or acute thrombosis. Following this evidence, Mg treatment may be necessary in CAD patients with Mg deficiency or acute myocardial infarction (AMI).

Serum concentrations of lipids and apolipoprotein E in angiographically defined coronary artery disease patients.

Apolipoprotein (apo) E is an important component of plasma lipoproteins and influences lipoprotein metabolism through its action as a receptor ligand. The association of serum apo E concentrations and coronary artery diseases (CAD) was investigated in 100 CAD patients (71 men, 29 women, mean age 62.0 years) and 155 healthy volunteers (87 men, 68 women, mean age 50.6 years). Patients with CAD had lower serum apo E concentrations (5.1+1.3 mg/dL) than the healthy volunteers (5.9+1.8 mg/dL, p <0.001). There were no significant differences between the number of disease vessels and the concentration of serum apo E. Serum apo E concentrations may have an anti-atherosclerotic effect and the serum apo E levels could be a useful parameter for defining cardiovascular risk factor.

Roxithromycin in prevention of acute coronary syndrome associated with Chlamydia pneumoniae infection: a randomized placebo controlled trial.

The role of Chlamydia pneumoniae infection in precipitating acute coronary syndrome (ACS) is unclear. Some studies have indicated that intervention with macrolide antibiotics might reduce coronary events in patients with ACS. A double blind, randomized, placebo-control trial was conducted on 84 ACS patients. Patients were randomized to 30 days of treatment with roxithromycin (150 mg, twice daily) or matching placebo. The follow-up period was 90 days, and the primary clinical end point included cardiovascular death, unplanned revascularization and recurrent angina/MI. Anti-C. pneumoniae IgG positive in 24 of 43 (55.8%) patients in the roxithromycin group and 23 of 41 (56.1%) patients in the placebo group. Anti-C. pneumoniae IgA positive in 20 of 43 (46.5%) patients in the roxithromycin group and 13 of 41 (31.7%) patients in the placebo group. Thirty-three cardiac events occurred (2 cardiovascular deaths, 9 CABG, 12 PTCA and 10 recurrent angina/MI) with 17 events in the roxithromycin group and 16 events in the placebo group. There was no significant difference of cardiac events between the roxithromycin and placebo groups. The present study suggests that antibiotic therapy with roxithromycin is not associated with reduction of cardiac events as reported by other investigators. However, therapeutic interventions may need to be specifically targeted to a group of patients who are confirmed with chronic C. pneumoniae infection.

Serum dehydroepiandrosterone sulfate, testosterone, and biochemical markers of bone turnover in elderly Thai men.

The most abundant human steroid, dehydroepiandrosterone sulfate (DHEAS), may have a multitude of beneficial effects, but declines with age. It is unclear whether DHEAS deficiency is an important factor contributing to increased bone resorption and impaired bone formation or not that leads to their bone loss. Thus, we investigated serum DHEAS, testosterone, osteocalcin (N-MID osteocalcin) and C-terminal telopeptides (beta-CrossLaps) in 121 healthy Thai males without bone diseases. Thirty-nine males (mean age 31.5 +/- 8.2, range 23-42 years) were recruited as the normal adult group and 82 males (mean age 61.2 +/- 7.0, range 52-77 years) were assigned as the elderly group. DHEAS levels were higher in the adult group compared with the elderly subjects (296.8 +/- 93.4 vs 172.6 +/- 99.8 microg/dL, p < 0.0001). Serum osteocalcin concentrations were also higher in the adult group compared with the elderly males (27.9 +/- 11.1 vs 23.2 +/- 7.9 ng/ml, p = 0.0091). However, serum testosterone and C-terminal telopeptides levels were not significantly different between the two groups. We concluded that low DHEAS concentrations are commonly encountered in elderly males and may relate to low osteocalcin levels due to the osteoblast stimulation effects of DHEAS. These findings may be implicated in the treatment of osteoporosis in elderly men by using DHEAS.

Prevalence of new coronary risk factors in Thai population.

Many new cardiovascular biomarkers of atherosclerosis have recently been emerging. However, there is a paucity of these data in the Thai population. This study aims to determine the prevalence of these biomarkers of atherosclerosis and the relationship between these new risk factors and other conventional risk factors for atherosclerosis in the healthy Thai population. As a yearly check-up program, we surveyed 3,615 normal healthy populations for their conventional risk factors and some new cardiovascular biomarkers for atherosclerosis. The authors found hyperhomocysteinemia and high level of Lp(a) in 27 per cent and 32 per cent of the cases respectively. Prevalence of recent and past chlamydial infection was found in 30 per cent and 51 per cent respectively.

Biochemical markers of bone turnover in angiographically-demonstrated coronary artery disease patients and healthy Thais.

The patients with coronary artery disease (CAD) were suffering from dyspnea. Physical activity of these patients was limited. Their lifestyle may be contributory factors for osteoporosis. Recent research has shown that biochemical markers may be used to predict future bone loss and identify individuals at risk for osteoporosis. Our objectives were to estimate reference ranges of bone markers in healthy Thais and to compare bone turnover between 105 healthy people and 118 CAD patients by using biochemical markers of bone formation and resorption. Mean values of bone markers in controls and patients were 22.9 +/- 12.9, 21.6 +/- 16.2 respectively for N-Mid osteocalcin and 0.45 +/- 0.30, 0.47 +/- 0.37 respectively for beta-Crosslaps. There was no statistical difference of N-Mid osteocalcin (p=0.50) and beta-Crosslaps (p=0.64) values between groups. Our data from this study suggested that that CAD patients have no higher risk for osteoporosis than healthy people.

Serum cardiac troponin T in unstable angina pectoris patients.

Cardiac troponin T (cTnT) is a regulatory contractile protein not normally found in blood. Its detection in the circulation has been shown to be a sensitive and specific marker for myocardial cell damage. In this study, we used a second-generation enzyme immunoassay for cTnT to determine whether its presence in the serum of patients with unstable angina was a prognostic indicator. Thirty patients with unstable angina pectoris (UAP) and 30 patients with Q-wave acute myocardial infarction (AMI) were screened for serum CK-MB activity and cTnT at 6, 12, 24 and 48 hours after the onset of chest pain, All of the mean concentrations of CK-MB activity determined in UAP patients were less than the upper limit of normal (25 U/L). Meanwhile, the mean concentration of cTnT at 6, 12, 24 and 48 hours after onset of chest pain were higher than the cutoff values (0.1 microg/L), We found that one third of UAP patients had serum cTnT at the time of admission more than 0.1 microg/L and that these groups of patients were associated with a high risk for cardiac events. Our results suggested that patients with elevated serum cTnT could be considered as high-risk patients for developing myocardial infarction, Patients with normal cTnT levels and a low or intermediate clinical risk could be stabilized and further stratified noninvasively.

Comparison of parathyroid hormone in angiographically-demonstrated coronary artery disease patients and healthy Thais.

Parathyroid hormone (PTH) influences the calcium metabolism. The idea of cardiovascular effects of PTH is not new. Target cells for PTH are cardiomyocytes and smooth muscle cells. Evidence from previous studies suggest that many patients with heart disease have elevated PTH concentrations. Our objective was to determine PTH status in patients with coronary artery disease (CAD). We compared intact PTH levels in 109 CAD patients with 103 healthy people by electrochemiluminescence immunoassay. Mean values of PTH in healthy Thais and CAD patients were 37.4 +/- 17.9 and 40.2 +/- 21.8 respectively. No statistical difference was shown. In addition, we compared PTH levels among various numbers of coronary occlusion and also found no differences. We propose that intact PTH concentrations in CAD patients are not higher than in the healthy population.

Seroprevalence of Chlamydia pneumoniae infection in Thailand.

Chlamydia pneumoniae (C. pneumoniae) is an emerging infectious agent, with a spectrum of clinical manifestations, and it has recently been tentatively linked to atherosclerosis. In order to describe the seroprevalence of C. pneumoniae in Thailand, we evaluated 1,798 normal healthy subjects (aged 20-93 years) for anti-C. pneumoniae IgG and IgA. Specific antibodies were measured by the fully automated ELISA method using elementary bodies of C. pneumoniae as an antigen. IgG antibodies against C. pneumoniae were presented in 55.16 per cent of men and 41.63 per cent of women. Anti-C. pneumoniae IgA were presented in 31.50 per cent of men and 27.49 per cent of women. The prevalence of IgG antibody increased with age and reached 78 per cent in subjects between 51-93 years. The pattern of IgA antibody was a saddle shape, which indicated 2 peaks of chronic infection. Our results suggested that C. pneumoniae infection was common in Thailand. The high prevalence of evidence of exposure to C. pneumoniae may have implications for the prevention of cardiovascular disease if further study concludes that infection with this organism is a risk for cardiovascular disease.

Correlation of serum lipoprotein(a) with the clinical presentation of Thai coronary artery disease patients.

Elevated serum levels of lipoprotein(a) [Lp(a)] confer an increased risk of coronary artery disease (CAD) and have been confirmed as a strong and independent risk factor for this disease. This case-control study was to determine the significance of elevated Lp(a) levels for the existence of CAD by systematically recording cardiovascular risk factors in diagnostic coronary angiography in a group of patients. Two hundred thirty seven consecutive patients (175 men, 62 women, aged 61+/-10 years) which comprised 24 acute myocardial infarction (AMI), 76 unstable angina (UA) and 137 stable angina (SA) who underwent coronary angiography, were used as cases. One hundred seventy normal healthy volunteers (95 men, 75 women, and aged 58+/-15 years) were used as controls. Lp(a) concentration were measured by an immunoturbidimetric method (Roche Diagnostics, Switzerland). There was a significant difference between Lp(a) levels in UA compared with the control subjects (44.2+/-49.0 vs. 27.6+/-25.3 mg/dL, p = 0.0006). When we compared SA and the control group (35.6+/-31.3 vs. 27.6+/-25.3 mg/dL, p = 0.0139) there was a significant difference between these two groups. UA patients also had a significantly higher prevalence of abnormal Lp(a) (>30 mg/dL) compared with the normal healthy control group (43.2% UA vs. 28.8% control, OR = 1.90, 95%CI = 1.08-3.32, p = 0.0248). SA patients also had the same finding as UA patients in a higher prevalence of abnormal Lp(a) when compared with the control group (45.2% SA vs. 28.8% control, OR = 2.04, 95%CI = 1.27-3.27, p = 0.0028). These data further support the role of Lp(a) in atherosclerotic coronary disease and the pathogenesis of acute coronary syndromes.

Myocardial injury after radiofrequency catheter ablation.

Radiofrequency catheter ablation has been a good treatment option for various types of cardiac arrhythmia. However there is concern about myocardial injury associated with radiofrequency catheter ablation. We studied myocardial injury with biochemical markers and echocardiogram in 41 consecutive patients who underwent electrophysiology study (EP study) and radiofrequency catheter ablation (RFCA) at our institute from April to July 2000. The concentration of biochemical markers (CK-MB mass, troponin T and myoglobin) and result of the echocardiograms were analyzed with other characteristics. In 41 patients subjected to EP study with possible RFCA, abnormal levels of troponin T, CK-MB mass and myoglobin were found in 46 per cent, 15 per cent and 44 per cent immediately after procedure, which went up to 64 per cent, 22 per cent and 2 per cent at twenty four hours. Compare to the group with normal troponin T level, the patients with abnormal level at 24 hours after RFCA had a longer procedure time (119+/-44 min. vs 90+/-22 min.), more frequent use of impedance ablation catheters (65% vs 27%), more RF applications (9+/-8 vs 18+/-16) and more ventricular ablation sites (69% vs 9%). The echocardiogram results showed no remarkable abnormality in any patients. Troponin T was the most sensitive marker to detect thermal myocardial injury associated with radiofrequency catheter ablation. Prolonged procedure time, RF applications, the use of impedance ablation catheter and ventricular ablation site were associated with elevated troponin T concentration after RFCA.

Analytical and clinical performance of two homogeneous assays for measuring of LDL-cholesterol.

A clinical laboratory currently estimates LDL-Cholesterol (LDL-C) concentration using the Friedewald calculation, which requires fasting specimens and is subject to error with increasing triglycerides levels. We evaluated the analytical and clinical performance of the direct LDL-C assay from two companies, Roche Diagnostics (LDL-C(Roche)) and Wako Pure Chemical (LDL-C(Wako)). Both methods meet current guidelines for precision with within-run coefficients of variation less than 3 per cent. The LDL-C(Roche) assay correlated well with the LDL-C from the Friedewald equation (LDL-C(Fried), r = 0.958, y = 0.85x + 17.08 mg/dL, n = 422). The LDL-C(Wako) assay also correlated with the LDL-C(Fried) (r = 0.946, y = 0.86x + 7.81 mg/dL, n = 422). In addition, at the medical decision cutoff points, LDL-C(Roche) assay and LDL-C(Wako) showed positive predictive values of 87.44 per cent and 69.67 per cent respectively. We conclude that the LDL-C(Roche) assay meets the currently established analytical and clinical performance, but LDL-C(Wako) assay meets only analytical performance. Clinical performance needs further evaluation.

Association between serum homocysteine, vitamin B12, folate and Thai coronary artery disease patients.

BACKGROUND: Homocysteine is an intermediate compound formed during metabolism of methionine. The plasma level of homocysteine is dependent on the genetically regulated level of essential enzymes and the intake of folic acid, vitamin B6 (pyridoxine), and vitamin B12 (cobalamine). Elevated serum homocysteine levels are a known risk factor for coronary artery disease (CAD). To establish the magnitude of the CAD that is associated with an increased serum homocysteine level, we compared CAD patients with normal healthy Thai controls. METHOD: In a cross-sectional study design we investigated the association between serum homocysteine, vitamin B12 and folate levels and the coronary heart disease in 178 CAD patients and 178 normal healthy controls by age and sex matching. These comprised 266 men and 90 women, mean age 58 +/- 10 years for normal controls and 60 +/- 10 years for CAD patients. Serum homocysteine, vitamin B12 and folate were measured by ELISA method and electrochemiluminescense method respectively. RESULTS: Paired t-test analysis showed that serum homocysteine concentrations were significantly higher in CAD patients (23.83 +/- 11.29 mumol/L) than in control subjects (19.69 +/- 8.51 mumol/L; p < 0.001). Homocysteine levels were also higher in males than in females. These findings were similar in healthy controls (male: 20.37 +/- 8.5 mumol/L, female: 17.77 +/- 8.2 mumol/L, p < 0.05) and in CAD patients (male: 24.91 +/- 11.8 mumol/L, female: 20.73 +/- 8.9 mumol/L, p < 0.05). Homocysteine above 17 mumol/L occurred more common in CAD patients than in control groups (OR = 1.65, 95% CI = 1.09-2.52, p = 0.0249). Low levels of vitamin B12 and folate did not reaching statistical significance when comparing controls and CAD patients. CONCLUSIONS: Serum homocysteine concentrations were significantly higher in CAD patients than in controls. Serum vitamin B12 and serum folate levels were not statistically significantly different between CAD patients and control groups. The data also demonstrated that the serum homocysteine level is almost always higher in men than in women as previously reported. Although serum vitamin B12 and serum folate levels were not below the upper limit of normal, vitamin B12 and folic acid treatment may reduce serum homocysteine concentrations in CAD patients. We hope that the reversible risk factors will be concern to clinicians for the reduction in the risk of myocardial infarction.

The prevalence of Chlamydia pneumoniae antibodies in Thai patients with coronary artery disease.

Blood samples were obtained from 243 consecutive coronary artery disease (CAD) patients (177 male, 66 female) aged 35-78 years (mean, 61 years) admitted for coronary angiography because of suspected coronary heart disease, and from 115 blood donors (91 male, 24 female) aged 25-60 years (mean, 47 years). Of the 243 CAD patients, 179 (74%) were positive by an ELISA method for Chlamydia pneumoniae antibodies IgG and 132 (54%) were positive for C. pneumoniae IgA. Among the 115 blood donors, 80 (70%) were positive for C. pneumoniae IgG and 49 (43%) were positive for C. pneumoniae IgA. When IgG antibodies were considered, there was no significant difference between CAD patients and healthy controls (OR = 1.29, 95% CI = 0.79-2.10, p > 0.05). In cases of positive IgA antibodies alone, there was a significant difference between CAD patients and healthy controls (OR = 1.58, 95% CI = 1.01-2.4, p = 0.029). If both IgG and IgA antibodies were positive, OR was increased from 1.58 to 1.80 (95% CI = 0.97-3.36, p = 0.044). In conclusion, C. pneumoniae infection is common in Thai people but chronic C. pneumoniae infection is more common in CAD patients than in middle-aged blood donors.