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Cancer of the prostate is the sixth most frequently found cancer in Singapore. Prostate-specific antigen (PSA) is the most clinically useful tumour marker available today for the diagnosis and management of prostate cancer. To enhance the value of PSA as a screening test we developed age-specific intervals for our ethnic population. The measurement of free PSA was included in the study to calculate the free:total ratio which enhances the differential diagnosis of prostate cancer from benign prostatic hyperplasia or prostatitis. The total PSA upper limits of 10-year intervals, beginning at 30-years-old, were 1.4, 1.7, 2.3, 4.0, 6.3 and 6.6 microg/l. Free PSA cut-off limits were 0.4, 0.5, 0.5, 1.0, 1.5 and 1.6 microg/l. The free:total ratio of PSA was not age dependent. Abbott AxSym standardised their calibration material for both free and total PSA assays with the Stanford 90:10 reference material. This laboratory has implemented these age-specific reference intervals and are currently following up their pick-up rate in the detection of prostate cancer.

Lipoprotein(a) [Lp(a)] is formed when apolipoprotein(a) is linked to low density lipoprotein (LDL)-cholesterol via a single disulfide bond. It is an independent risk factor for myocardial infarction and raised concentrations are associated with an increased risk of developing coronary artery disease. Singapore has a multi-racial population of 77% Chinese, 14% Malays and 7% Indians. Studies have shown that the Indians have significantly higher standardised mortality ratios (SMR) compared to the Chinese and the Malays. We measured serum Lp(a) concentrations in 803 healthy individuals recruited from the Multiphasic Health Screening Programme, using the Macra Lp(a) sandwich enzyme immunoassay kit (Strategics Diagnostics, Delaware, USA). Lp(a) concentrations were skewed in all three groups. Our population mean was 9.0 mg/dl, with 50th, 75th and 95th percentile values of 10.2, 19.8 and 43.1 mg/dl, respectively, which are lower than values reported from Caucasian populations (15.0, 29.0 and 60.0 mg/dl, respectively). Males had lower Lp(a) concentrations than females (P < 0.05). The Indian group had significantly higher concentrations (median 12.3 mg/dl) compared to their Chinese (median 9.6 mg/dl) and Malay (median 8.4 mg/dl) counterparts (P < 0.05). This could partly account for the higher SMR seen in the Indian population in Singapore. As serum Lp(a) concentrations are method- and population-dependent, we recommend that laboratories determine their own reference ranges by their method to avoid misclassification of the coronary heart disease (CHD) risk of patients.

The allele frequencies for the apolipoprotein B (apo B) 5'-Ins/Del and 3'-VNTR polymorphisms varied significantly (p < 0.01) among Singaporeans of Chinese, Malay and Indian descent. We calculated the unbiased expected heterozygosities for the 5'-Ins/Del polymorphism as 0.3357, 0.1984 and 0.2418, and for the 3'-VNTR as 0.5980, 0.5260 and 0.6749, respectively, in the Chinese, Malays and Indians. Compared to heterozygosities reported for other populations, the Singaporeans differed from most Caucasians in having significantly lower values but were closely related to other non-Caucasians. Thirteen alleles, with a bimodal distribution, were observed at the 3'-VNTR polymorphic locus; the alleles occurring most frequently among the Chinese and Malays were of 35 or 53 repeats, and among the Indians, of 37 or 47 repeats. The Del allele was associated with elevated serum cholesterol (p = 0.023), LDL-cholesterol (LDL-C) (p = 0.001) in the Chinese, and apo B (p = 0.007) in the Indians. Likewise, the larger 3'-VNTR alleles (> 41 repeats) were associated with raised cholesterol (p = 0.018), LDL-C (p = 0.025), and triglyceride (p = 0.001) in the Chinese. The two polymorphisms were not in significant linkage disequilibrium (D = -0.0029, p = 0.494) in the three ethnic groups.

Cardiovascular risk factors were compared between 126 people with non-insulin-dependent diabetes mellitus (NIDDM) and 530 non-diabetics (controls), in a random sample of people (Chinese, Malays, and Asian Indians) aged 40-69 years from the general population of Singapore. Data were adjusted for age and ethnicity. For both genders, people with NIDDM had higher mean body mass indices, waist-hip ratios and abdominal diameters. They also had a higher prevalence of hypertension, higher mean levels of fasting serum triglyceride, slightly lower mean levels of serum high-density-lipoprotein cholesterol, and higher mean levels of plasma plasminogen activator inhibitor-1 and tissue plasminogen activator (antigen). These factors are components of syndrome X (metabolic syndrome) and increase the risk of atherosclerosis and thrombosis. In contrast, there were no important differences for cigarette smoking, serum total and low-density-lipoprotein cholesterol, serum apolipoproteins A1 and B, plasma factor VIIc and plasma prothrombin fragment 1 + 2. Females with NIDDM, but not males, had a higher mean serum fibrinogen level than non-diabetics, which could explain why NIDDM has a greater cardiovascular effect in females than males. Serum lipoprotein(a) concentrations were lower in people with NIDDM. Mean levels of serum ferritin, a pro-oxidant, were higher in people with NIDDM than controls, but there were no important differences for plasma vitamins A, C and E, and serum selenium, which are anti-oxidants.

Study Objective: To examine the hypothesis that the higher rates of coronary heart disease (CHD) in Indians (South Asians) compared with Malays and Chinese is at least partly explained by central obesity, insulin resistance, and syndrome X (including possible components)., Design: Cross sectional study of the general population., Setting: Singapore., Participants: Random sample of 961 men and women (Indians, Malays, and Chinese) aged 30 to 69 years., Main Results: Fasting serum insulin concentration was correlated directly and strongly with body mass index (BMI), waist-hip ratio (WHR), and abdominal diameter. The fasting insulin concentration was correlated inversely with HDL cholesterol and directly with the fasting triglyceride concentration, blood pressures, plasminogen activator inhibitor 1 (PAI-1), and tissue plasminogen activator (tPA), but it was not correlated with LDL cholesterol, apolipoproteins B and A1, lipoprotein(a), (Lp(a)), fibrinogen, factor VIIc, or prothrombin fragment (F)1 + 2. This indicates that the former but not the latter are part of syndrome X. While Malays had the highest BMI, Indians had a higher WHR (men 0.93 and women 0.84) than Malays (men 0.91 and women 0.82) and Chinese (men 0.91 and women 0.82). In addition, Indians had higher fasting insulin values and more glucose intolerance than Malays and Chinese. Indians had lower HDL cholesterol, and higher PAI-1, tPA, and Lp(a), but not higher LDL cholesterol, fasting triglyceride, blood pressures, fibrinogen, factor VIIc, or prothrombin F1 + 2., Conclusions: Indians are more prone than Malays or Chinese to central obesity with insulin resistance and glucose intolerance and there are no apparent environmental reasons for this in Singapore. As a consequence, Indians develop some but not all of the features of syndrome X. They also have higher Lp(a) values. All this puts Indians at increased risk of atherosclerosis and thrombosis and must be at least part of the explanation for their higher rates of CHD.