Bassam A. Nassar

Bone turnover markers in the management of postmenopausal osteoporosis

Osteoporosis is the most common cause of fragility fractures. Bone remodelling is essential for repairing damaged areas within bone to preserve bone strength and for assisting in mineral homeostases. In young adults, bone remodelling is usually balanced with approximately as much bone replaced as is removed during each remodelling cycle. However, when remodelling becomes accelerated in combination with an imbalance that favours bone resorption over formation, such as during menopause, precipitous losses in bone mass occur. Bone turnover markers (BTMs) measure the rate of bone remodelling allowing for a dynamic assessment of skeletal status and hold promise in identifying those at highest risk of rapid bone loss and subsequent fracture. Further, the use of BTMs to monitor individuals administered osteoporosis therapy is attractive as monitoring anti-fracture efficacy with bone mineral density has significant limitations. This review details remodelling biology, pre-analytical and analytical sources of variability for BTMs, describes the most commonly used resorption and formation markers, and offers some guidelines for their use and interpretation in the laboratory and the clinic.

Relation of genetic polymorphisms of apolipoprotein E, angiotensin converting enzyme, apolipoprotein B-100, and glycoprotein IIIa and early-onset coronary heart disease.

OBJECTIVE Apolipoprotein E (APOE) E4, apolipoprotein B-100 (APOB) Q3611 allele, the angiotensin converting enzyme (ACE) deletion (D) allele and glycoprotein IIIa (GP3A) P33 mutant allele are reported to predispose to early-onset coronary heart disease (CHD). These associations were not all confirmed in more recent studies. To determine the impact of these alleles on CHD, we examined the prevalence of these mutations in patients presenting with early-onset CHD and compared them to those manifesting CHD later in life. The delayed-onset was considered a sign of longevity and would serve as a comparative group to assess prevalence of the biochemical and genetic risk factors. METHODS 300 patients with a history of myocardial infarction or angina pectoris and angiographically documented CHD were studied. Patients were divided into two groups: group 1 (G1 = 150 patients) presenting with these findings under the age of 50 years; while group 2 (G2 = 150 patients) were patients presenting for the first time over the age of 65 years. Prevalence of the alleles of APOE, APOB, ACE and GP3A was assessed by molecular analysis. An association of any of these genotypes with early onset CHD could lead to a higher prevalence in the younger age group. RESULTS AND CONCLUSIONS None of the suspected alleles namely APOB Q3611 [G1: 10.7% vs. G2: 9.0%, p = 0.57], ACE D (G1: 52.0% vs. G2: 49.7%, p = 0.57), or the GP3A P33 (G1: 17.3% vs. G2: 15.7%; p = 0.58) showed any significant difference between the two groups. Subjects with APOE E4 were more frequent in the younger age group (G1: 18.3% vs. G2: 13.7%; p = 0.047), while APOE E2 was more frequent in G2 (G2: 10.0% vs. G1: 2.7%; p = 0.0002). Multivariate analysis showed an odds ratio of APOE E2 allele in G1 of 0.27 with a confidence interval of 0.10-0.73.

Relation of a Common Mutation in Methylenetetrahydrofolate Reductase to Plasma Homocysteine and Early Onset Coronary Artery Disease

OBJECTIVE In the presence of low serum folate, mutant 5,20-methylenetetrahydrofolate reductase (MTHFR + [A223V/C677T]) in the homozygous state (+/+), may predispose to higher plasma homocysteine (tHct) levels and coronary artery disease (CAD). To determine the impact of this relationship on predisposition to early-onset CAD, we examined the prevalence of the mutation and plasma tHct in patients with early-onset CAD and compared them to patients manifesting CAD later in life. METHODS Three hundred patients with history of acute myocardial infarction or angina pectoris and angiographically documented CAD were studied. Patients consisted of two groups: group 1 (G1 = 150 patients) presenting with these findings under age 50; while group 2 (G2 = 150) presented for the first time over age 65 years. Prevalence of the MTHFR+ mutation was assessed by molecular analysis, and plasma tHct and folate were measured. An association of the +/+ genotype with early onset CAD could lead to its higher prevalence in the younger age group. RESULTS There was no significant difference in the frequency of the (+/+) genotype between the two groups (G1: 11.3% vs. G2: 11.3%). However, patients with the (+/+) genotype in both groups had higher tHct when plasma folate was below the mean value (G1: p < 0.0001 while G2: p < 0.01). CONCLUSION The mutant MTHFR genotype was not found to be a determining factor in early-onset CAD. Higher tHct values were obtained in the older age group, which is expected because other studies have shown that tHct levels increase with age. A significant relation was shown between MTHFR genotype and low folate status yielding high tHct levels in those with the (+/+) genotype. As this relation was seen in both groups, although to a lesser extent in the older G2, it does not explain the underlying cause of early-onset CAD.

Apolipoprotein E-polymorphism, frailty and mortality in older adults

Although apolipoprotein E (ApoE) polymorphism is associated with variable risks of several illnesses, and with mortality, no persuasive relationship has been demonstrated with frailty. Here, the clinical examination cohort (n= 1452 older adults, aged 70+ years at baseline) of the Canadian Study of Health and Aging was evaluated, with 5‐year follow‐up data. Frailty was defined using both the phenotypic definition from the Cardiovascular Health Study (Frailty‐CHS) and the ‘Frailty Index’, from which age‐specific trajectories of deficit accumulation can be estimated. In age‐sex adjusted analyses, people with ApoE 4 allele had a higher risk of death (hazard ratio [HR]= 1.20; 95% confidence interval: 1.01–1.45), but this relationship was not significant when adjusted for cognitive impairment (1.06; 95% confidence interval: 0.88–1.27). There was no association between frailty and ApoE polymorphism, defined in age‐sex adjusted models either as Frailty‐CHS (ApoE4 HR 1.17; 95% confidence interval: 0.98–1.40, frailty HR 1.37; 95% confidence interval: 1.28–1.46) or by the Frailty Index (ApoE4 HR 1.07; 95% confidence interval: 0.90–1.29, frailty HR 35.3; 95% confidence interval: 20.4–61.1). The data do not support an association between ApoE polymorphism and frailty. This result did not depend on how frailty was defined.

Relation between butyrylcholinesterase K variant, paraoxonase 1 (PON1) Q and R and apolipoprotein E ϵ4 genes in early-onset coronary artery disease

OBJECTIVES The common K variant of butyrylcholinesterase (BChE-K), an enzyme which metabolizes acetylcholine and organophosphates, has been associated with Alzheimers disease, especially in the presence of the apolipoprotein E epsilon 4 allele (APOE-epsilon 4). Although APOE-epsilon 4 has been associated with the development of coronary artery disease (CAD), an association between the BChE-K variant and CAD has not been explored. Paraoxonase 1 (PON1), located within HDL, is an enzyme which also metabolizes organophosphates and may be antiatherogenic. The R192 variant of PON1 (PON1-R) has been associated with CAD. DESIGN AND METHODS To determine whether BChE-K is also associated with premature CAD, we examined the frequency of BChE-K among patients with early-onset CAD (n = 150; < 50 yr) vs. late-onset CAD (n = 150; > 65 yr) by molecular analysis. We also examined the frequency of the PON1-R allele in both groups, and explored whether there was synergism between BChE-K and APOE-epsilon 4, BChE-K and PON1-R or PON1-R and APOE-epsilon 4. RESULTS The frequency of the BChE-K allele tended to be greater among early-onset CAD patients compared to late-onset CAD patients (41.3% vs. 31.3%; p = 0.07), but without any significant difference between males and females. There was no difference in the prevalence of the PON1-R allele between those with early- or late-onset CAD (46.0% vs. 52.7%; p = 0.25). Twenty-two patients with early-onset CAD had both the BChE-K plus APOE-epsilon 4 alleles (14.7%) compared to 11 late-onset CAD patients (7.3%) (p = 0.04). There was no such association between BChE-K and PON1-R, nor PON1-R and APOE-epsilon 4. CONCLUSIONS Our study suggests that there is a minor association between BChE-K and early-onset CAD, especially in the presence of the APOE-epsilon 4 allele.

Role of the fractalkine receptor CX3CR1 polymorphisms V249I and T280M as risk factors for early‐onset coronary artery disease in patients with no classic risk factors

Objectives. CX3CR1 is a monocyte chemokine receptor and adhesion molecule. Two CX3CR1 mutations, V249I and T280M, reportedly decrease coronary artery disease (CAD) risk independent of established risk factors. An I249 protective effect is attributed to reducing CX3CR1 binding to fractalkine, its ligand. Material and methods. We examined the frequencies of V249I and T280M among early‐onset CAD patients (G1; n = 149; <50 years), late‐onset CAD patients (G2; n = 150; >65 years) and healthy controls (HC; n = 149, 47–93 years) without known CAD risk factors. We compared plasma total cholesterol (TC)/high density lipoprotein‐C (HDL‐C) and apolipoprotein B (APOB)/apolipoprotein AI (APOAI) ratios among the groups and mutation carriers and non‐carriers, and the prevalence of the mutations in G1 and G2 patients with multiple coronary vessel disease (MVD) and myocardial infarction (MI). Results. G1 patients had non‐significantly lower frequencies of I249 versus (vs.) G2 or controls (G1; 51 %, G2: 61 %, controls: 58 %, p = 0.19), with no difference in T280M (p = 0.8). TC/HDL‐C and APOB/APOAI ratios were significantly higher in G1 patients vs. G2 and controls (p<0.0001) independently of either mutation. More G2 patients had MVD than younger ones (p<0.0001); however, more G1 patients were homozygous for V249 compared to G2 patients, who more often had the I249 allele (p<0.02). There was no such association with T280M (p = 0.38). Although more G1 patients had MI, this was not mutation related. Conclusions. There were significantly higher lipid ratios in G1 compared to G2 and HC (G1>G2>HC), but not in mutation prevalence. I249 mutation was associated with MVD in older patients, while V249 homozygosity was associated with the early‐onset CAD. Neither allele affected MI or lipid levels.

An effective utilization management strategy by dual approach of influencing physician ordering and gate keeping.

OBJECTIVES There is increasing recognition of the importance of appropriate laboratory test utilization. We investigate the effect of a multifaceted educational approach that includes physician feedback on individual test ordering, in conjunction with targeted restriction, on the utilization of selected laboratory tests. DESIGN AND METHODS Scientific evidence was compiled on the usefulness and limitations of tests suspected of being over utilized in our laboratories. A variety of approaches were used to deliver education on each of the targeted tests, with greater focus on primary care physicians (PCPs). Feedback on requesting behavior of these tests was also communicated to the latter group which included an educational component. Laboratory based restriction of testing was also exercised, including the unbundling of our electrolyte panel. RESULTS PCP requesting patterns for the selected tests were found to be markedly skewed. The interventions implemented over the study period resulted in a substantial 51% reduction in overall ordering of five of the targeted tests equating to an annual marginal cost saving of

Detection of familial defective apolipoprotein B-100 among patients clinically diagnosed with heterozygous familial hypercholesterolemia in maritime Canada

60,124. Unbundling of the electrolyte panel resulted in marginal cost savings that equated annually to

Pushing the limits of chemistry point-of-care testing for the management of patients under investigation for Ebola virus disease

42,500 on chloride and

Multiple pre- and post-analytical lean approaches to the improvement of the laboratory turnaround time in a large core laboratory

48,000 on total CO2. CONCLUSIONS A multifaceted educational approach combined with feedback on utilization and laboratory driven gate-keeping significantly reduced the number of laboratory tests suspected of being redundant or unjustifiably requested. Laboratory professionals are well positioned to manage demand on laboratory tests by utilizing evidence base in developing specific test ordering directives and gate-keeping rules.