Reflective testing: how useful is the practice of adding on tests by laboratory clinicians?

AIMS: To investigate the clinical value and practice of reflective testing, a new term to describe the practice of adding on tests when reporting or clinically authorising results. METHODS: A consultant medical biochemist collected over a calendar year (2001) copies of clinical biochemistry reports on samples to which he had added on either iron studies (iron, total iron binding capacity (TIBC), and percentage saturation), or vitamin D. Iron studies and vitamin D were added on when biochemical results, available clinical information, demographic data, and clinical experience-or combinations thereof-suggested the possibility of haemochromatosis or vitamin D deficiency, respectively. The number of reports that the consultant authorised was estimated for the same calendar year. The number and percentage of raised TIBC percentage saturation and low vitamin D results from the tests that were added on were collated. RESULTS: Raised TIBC saturation values were found in 28 patients (18.7% of the iron studies added on), of whom 16 were subsequently genotyped, eight having a genotype consistent with haemochromatosis. Thirty one patients with vitamin D deficiency (23.1% of the vitamin D tests added on) were identified. CONCLUSIONS: The addition of iron studies and vitamin D tests by a laboratory clinician, when reporting, resulted in the identification of patients with haemochromatosis and vitamin D deficiency. The practice of adding on tests should be called reflective testing, because it is discretionary and is based on the clinical judgement of a laboratory clinician in the interpretation of results.

Urinary excretion of salicyluric and salicylic acids by non-vegetarians, vegetarians, and patients taking low dose aspirin.

AIM: To compare amounts of salicyluric acid (SU) and salicylic acid (SA) excreted daily in the urine of non-vegetarians and vegetarians not taking salicylate drugs, and patients taking 75 or 150 mg aspirin/day. METHODS: Urine excreted over 24 hours was collected from volunteers in the four groups. The volumes were recorded and the concentrations of SU and SA were determined electrochemically after separation by high performance liquid chromatography. RESULTS: Significantly more SU was excreted daily by vegetarians (median, 11.01; range, 4.98-26.60 micro mol/24 hours) than by non-vegetarians (median, 3.91; range, 0.87-12.23 micro mol/24 hours), although amounts were significantly lower than those excreted by patients taking aspirin. Median amounts of SU excreted by patients taking 75 and 150 mg/day of low dose aspirin were 170.69 (range, 13.15-377.18) micro mol/24 hours and 165.17 (range, 5.61-429.12) micro mol/24 hours, respectively. The amount of SU excreted by patients taking either 75 or 150 mg of aspirin/day was not significantly different. Significantly more SA was excreted by vegetarians (median, 1.19; range, 0.02-3.55 micro mol/24 hours) than by non-vegetarians (median, 0.31; range, 0.01-2.01 micro mol/24 hours). The median amounts of SA excreted by vegetarians and the patients taking aspirin were not significantly different. CONCLUSIONS: More SU and SA is excreted in the urine of vegetarians than in non-vegetarians, consistent with the observation that fruits and vegetables are important sources of dietary salicylates. However, significantly less SU was excreted by vegetarians than patients taking aspirin, indicating that the daily intake of bioavailable salicylates by vegetarians is considerably lower than that supplied by a single 75 or 150 mg dose of aspirin.

Identification and determination of salicylic acid and salicyluric acid in urine of people not taking salicylate drugs.

BACKGROUND: Salicylic acid (SA) is present in the serum of people who have not taken salicylate drugs. Now we have examined the urine of these subjects and found that it contains SA and salicyluric acid (SU). We have established the identities of these phenolic acids and determined their concentrations. METHODS AND RESULTS: The acidic hydrophobic compounds of urine were separated using high-performance liquid chromatography (HPLC) and were detected and quantified electrochemically. Two approaches were used to establish the identity of SA and SU. First, the retention times (Rt) of the substances extracted and those of SA and SU were compared under two sets of chromatographic conditions; the Rt of the compounds suspected to be SA and SU and those of the authentic substances were very similar under both sets of conditions. Second, the unknown substances, isolated by HPLC, were treated with acetyl chloride in methanol and compared with the methyl esters of SA and SU by using gas chromatography-mass spectrometry; the unknown compounds after esterification had very similar mass spectra and gas chromatographic R, to those of methyl salicylate and methyl salicylurate. The median (n = 10) urinary concentration of SA was 0.56 micromol/L (range 0.07-0.89 micromol/L) and that of SU was 3.20 micromol/L (range 1.32-6.54 micromol/L). SA and its major urinary metabolite, SU, were found in the urine of all of the 10 people examined.

Salicylic acid: a link between aspirin, diet and the prevention of colorectal cancer.

Aspirin was introduced into clinical practice more than 100 years ago. This unique drug belongs to a family of compounds called the salicylates, the simplest of which is salicylic acid, the principal metabolite of aspirin. Salicylic acid is responsible for the anti-inflammatory action of aspirin, and may cause the reduced risk of colorectal cancer observed in those who take aspirin. Yet salicylic acid and other salicylates occur naturally in fruits and plants, while diets rich in these are believed to reduce the risk of colorectal cancer. Serum salicylic acid concentrations are greater in vegetarians than non-vegetarians, and there is overlap between concentrations in vegetarians and those taking low-dose aspirin. We propose that the cancer-preventive action of aspirin is due to its principal metabolite, salicylic acid, and that dietary salicylates can have the same effect. It is also possible that natural salicylates contribute to the other recognized benefits of a healthy diet.

Salicylic acid in the serum of subjects not taking aspirin. Comparison of salicylic acid concentrations in the serum of vegetarians, non-vegetarians, and patients taking low dose aspirin.

AIMS: To determine serum salicylic acid concentrations in non-vegetarians and vegetarians not taking salicylate drugs, and to compare these concentrations with those found in patients taking aspirin, 75 mg daily. METHODS: Serum samples were obtained from vegetarians (n = 37) and non-vegetarians (n = 39) not taking salicylate drugs. Non-vegetarians and vegetarians were recruited from the community and from a Buddhist monastery, respectively, in Dumfries and Galloway, Scotland. Patients (n = 14) taking aspirin (75 mg daily) were recruited from the Dumfries diabetic clinic. Serum salicylic acid concentrations were determined using a high performance liquid chromatography method with electrochemical detection. RESULTS: Salicylic acid was detected in every serum sample analysed. Higher serum concentrations of salicylic acid were found in vegetarians than non-vegetarians: median concentrations of 0.11 (range, 0.04-2.47) micromol/litre and 0.07 (range, 0.02-0.20) micromol/litre, respectively; the median of the difference was 0.05 micromol/litre (95% confidence interval for difference, 0.03 to 0.08; p < 0.0001). The median serum concentration of salicylic acid in patients taking aspirin (75 mg daily) was 10.03 (range, 0.23-25.40) micromol/litre, which was significantly higher than that found in non-vegetarians and vegetarians. There was overlap in serum salicylic acid concentrations between the vegetarians and patients taking aspirin. CONCLUSIONS: Salicylic acid, a non-steroidal anti-inflammatory drug, is present in fruits and vegetables and is found in higher concentrations in vegetarians than non-vegetarians. This suggests that a diet rich in fruits and vegetables contributes to the presence of salicylic acid in vivo. There is overlap between the serum concentrations of salicylic acid in vegetarians and patients taking aspirin, 75 mg daily. These findings may explain, in part, the health promoting effects of dietary fruits and vegetables.

Salicylic acid in soups prepared from organically and non-organically grown vegetables.

BACKGROUND: Salicylic acid is a chemical signal in plants infected by pathogens and it is responsible for the anti-inflammatory action of aspirin. Patients who take aspirin have a reduced risk of developing atherosclerosis and colorectal cancer, both of these pathologies having an inflammatory component. Dietary salicylic acid may help to prevent these conditions. We wondered if foods made from organically-reared plants might have a higher content of salicylic acid than those made from non-organic plants, since the latter are more likely to be protected from infection by the application of pesticides. OBJECTIVE: To determine if organic vegetable soups have a higher salicylic acid content than non-organic vegetable soups. METHODS: The contents of salicylic acid in organic and non-organic vegetable soups purchased from supermarkets were determined. Salicylic acid was identified by varying the chromatographic conditions and comparing the retention times of the unknown substance in the extracts with salicylic acid; by treating extracts of the soups with salicylate hydroxylase; and by using GCMS. Salicylic acid was determined by using HPLC with electrochemical detection. RESULTS: Salicylic acid was present in all of the organic and most of the non-organic vegetable soups. The median contents of salicylic acid in the organic and non-organic vegetable soups were 117 (range, 8-1040) ng x g(-1) and 20 (range, 0-248) ng x g(-1) respectively. The organic soups had a significantly higher content of salicylic acid (p=0.0032 Mann Whitney U test), with a median difference of 59 ng g(-1) (95 % confidence interval, 18-117ng x g(-1)). CONCLUSIONS: Organic vegetable soups contained more salicylic acid than non-organic ones, suggesting that the vegetables and plants used to prepare them contained greater amounts of the phenolic acid than the corresponding non-organic ingredients. Consumption of organic foods may result in a greater intake of salicylic acid.

Identifying patients at risk for coronary heart disease: implications from trials of lipid-lowering drug therapy.

Abnormal lipid levels contribute significantly to the risk of coronary heart disease (CHD), which is increased further in the presence of other risk factors. The association between elevated low-density lipoprotein (LDL) cholesterol and CHD risk is well established, and large primary and secondary prevention studies of HMG-CoA reductase inhibitors (statins) have shown conclusively that lowering LDL cholesterol levels reduces CHD events and total mortality. Regardless of the intervention used (diet, surgery, drugs), reduction of plasma cholesterol has consistently produced a reduction in cardiovascular risk. Absolute benefit is greatest in those who are at highest risk initially, and trial results suggest that the lower the LDL cholesterol level achieved, at least down to LDL of 3.0 mmol/l, then the lower is the CHD event risk. Epidemiological data also point to the negative impact of other lipids on CHD risk. Low levels of high-density lipoprotein (HDL) and high levels of triglycerides (particularly in conjunction with an LDL/HDL ratio >5) are particularly strong risk factors for CHD. Thus, although prevention trials to date have primarily assessed the impact of LDL lowering on CHD events, the initial assessment of CHD risk should consider a more detailed atherogenic profile including HDL and triglyceride levels. A general approach to preventing cardiovascular disease should include strategies to reduce the overall CHD risk by lifestyle modification and management of modifiable risk factors such as smoking, hypertension and diabetes. Based on data from recent prevention studies, and because they are the most potent lipid-lowering agents available for lowering LDL cholesterol, statins have appropriately become the drug of choice for most patients with hyperlipidaemia who require drug therapy.

The identification of salicylates as normal constituents of serum: a link between diet and health?

AIM: To examine sera for the presence of salicylic acid and 2,3- and 2,5-dihydroxybenzoic acids (2,3- and 2,5-DHBA), in individuals not taking salicylate drugs. METHODS: Extracts of acidified serum samples were analysed by high performance liquid chromatography with electro-chemical detection. The chromatographic conditions were altered, and the retention times of the unknown compounds compared against authentic salicylic acid, 2,3-DHBA, and 2,5-DHBA. Serum samples (some spiked with salicylic acid) were incubated with salicylate hydroxylase and analyses undertaken. An extract of acidified serum was derivatised using N-methyl-N-trimethylsilyltrifluoroacetamide and the salicylic acid derivative identified by gas chromatography-mass spectrometry. RESULTS: Salicylic acid, 2,3-DHBA, and 2,5-DHBA were identified as being normal constituents of serum. CONCLUSIONS: Salicylic acid, 2,3-DHBA, and 2,5-DHBA possess anti-inflammatory properties. The finding that these compounds are present as normal constituents of serum, possibly arising from diet, raises important questions as to their role in the promotion of health.

Clinical and biochemical determinants of plasma lipid peroxide levels in type 2 diabetes.

The enhanced risk and increased severity of atheroma in diabetes is well recognized but, as yet, incompletely explained. A cross-sectional study of vascular disease risk factors in a group of type 2 diabetic patients from South West Scotland has revealed an association between glycaemic control, assessed by HbAl level and plasma lipid peroxides measured by a specific high-performance liquid chromatography method. Duration of diabetes appeared to be a subsidiary contributor to lipid peroxidation. We suggest this evidence supports the importance of glycaemic control in modulating glyco-oxidative mechanisms probably crucial to production of diabetic complications. Atherosclerosis prevention in diabetes may hinge on exemplary simultaneous control of both hyperglycaemia and hyperlipidaemia.

Human vascular smooth muscle cells express receptors for CC chemokines.

Arteriosclerotic lesions are characterized by the accumulation of T lymphocytes and monocytes and the proliferation of intimal smooth muscle cells. Expression of the chemokine monocyte chemoattractant protein-1 (MCP- 1) has been observed in arteriosclerotic plaques and has been proposed to mediate the transendothelial migration of mononuclear cells. More recently, MCP-1 has been proposed to affect the proliferation and migration of vascular smooth muscle cells (VSMCs). We have used reverse transcription-polymerase chain reaction (RT-PCR) to investigate chemokine mRNA expression in human arteriosclerotic lesions obtained from surgical biopsy of diseased vascular tissue and show, in addition to MCP-1, expression of the chemokine macrophage inflammatory protein-1alpha (MIP-1alpha) at higher levels than in "normal" aortic tissue. We have also used RT-PCR to characterize the expression of known chemokine receptors by primary human VSMCs. Messenger RNA for the MIP-1alpha/RANTES receptor, CCR-1, and the MCP-1/MCP-3 receptor, CCR-2, was expressed by unstimulated VSMCs grown under serum-free culture conditions for 24 hours. The receptors CCR-3, CCR-4, CCR-5, CXCR-1, and CXCR-2 were not expressed by VSMCs. The presence of functionally coupled receptors for MIP-1alpha on VSMCs was demonstrated by specific binding of biotinylated MIP-1alpha and increases in intracellular Ca2+ levels after exposure to this chemokine. Taken together, these results suggest that chemokines are likely to be involved in arteriosclerosis and may play a role in modulating the function of VSMCs in vivo.

Serum creatinine and urea: make the most of these simple test.

The most frequently requested measurements of renal function are serum urea and creatinine. This article describes how to make the most of these simple tests in the assessment of patients with renal disease.

Plasma lipid peroxide and serum vitamin E levels in subjects taking antipsychotic drugs.

Fourteen non-schizophrenic subjects were identified in a group general practice as taking antipsychotic medication. They were matched with a control group on age, gender and smoking status. Blood samples were taken to measure plasma lipid peroxide, serum vitamin E and cholesterol and vitamin E:cholesterol ratios. The majority of subjects were taking thioridazine (mean daily dose 42 mg, range 20-100 mg). There were no statistically significant differences between subjects and controls in any of the laboratory measures. The results in this small study therefore do not support the hypothesis that a possible source of increased free radical activity in schizophrenic patients is antipsychotic medication.

The Nithsdale Schizophrenia Surveys. XIV: Plasma lipid peroxide and serum vitamin E levels in patients with and without tardive dyskinesia, and in normal subjects.

BACKGROUND: Tardive dyskinesia (TD) may be mediated through free radical damage to neurons. Plasma lipid peroxide levels are a measure of radical damage to fats. Vitamin E is a free radical scavenger. METHOD: One hundred and twenty-eight schizophrenic patients were examined for TD using the Abnormal Involuntary Movements Scale. Blood samples were taken to measure plasma lipid peroxide, serum vitamin E and cholesterol, and vitamin E:cholesterol ratios. Twenty-four patients were also examined in October 1993, January 1994, and April 1994. Biochemical results were compared in 81 patients and 79 normal subjects. RESULTS: Patients with and without TD did not differ in median plasma lipid peroxide and serum vitamin E levels, or vitamin E:cholesterol ratios. Correlations between seasonal change scores in TD and biochemical measurements were low. Lipid peroxide levels were higher and vitamin E:cholesterol ratios lower in patients than in normal subjects. Vitamin E levels were lowest in in-patients and in those living in supported accommodation. CONCLUSIONS: The results do not support the hypothesis that TD is mediated through free radical damage to neurons, but suggest increased free radical activity in schizophrenia.

On-call duties in chemical pathology: a survey of junior medical staff in the UK.

To ascertain the extent of variation in out-of-hours duties among trainees in chemical pathology in the UK questionnaires were sent to 81 junior medical staff in 1992. Replies were received from 63 (78%). Although most had participated in an advisory rota, only 41 (65%) had participated in an analytical rota. Nine (14%) had participated in specialist analytical rotas, while 13 (21%) had experience of multidisciplinary rotas and only eight (13%) had experience of rotas involving clinical responsibility. Only 10 (16%) regularly reviewed their work on call with their senior medical staff. There was no single method of requesting tests out of hours in the trainees' laboratories and there was also considerable variation with respect to the tests available out of hours. It is concluded that sufficient variation exists in the on-call experience gained by junior medical staff in chemical pathology to raise concern about the quality of training in out-of-hours work.

A comparison of different methods of assessing free radical activity in type 2 diabetes and peripheral vascular disease.

Increased free radical activity in diabetes mellitus may contribute to the higher prevalence and mortality from macrovascular disease in diabetic patients. To investigate this, levels of plasma antioxidants (superoxide dismutase, caeruloplasmin, plasma, and lysate thiol), diene conjugates, lipid peroxides, and chemiluminescence were measured in diabetic and non-diabetic patients with peripheral vascular disease compared with healthy control subjects. Caeruloplasmin, diene conjugate ratio, and lipid peroxides were significantly increased in patients with vascular disease but there was no difference between diabetic and non-diabetic patients. Conjugated diene ratio correlated with caeruloplasmin (r = 0.40, p < 0.02) and inversely with superoxide dismutase level (r = 0.36, p < 0.05) but there was no significant correlation between other antioxidants and diene conjugates, lipid peroxides or chemiluminescence. The relationship between different indirect measurements of free radical activity is variable but there appears to be no additive effect of diabetes on the increased free radical activity associated with vascular disease.