Symptoms and other factors associated with time to diagnosis and stage of lung cancer: a prospective cohort study.

BACKGROUND: This prospective cohort study aimed to identify symptom and patient factors that influence time to lung cancer diagnosis and stage at diagnosis. METHODS: Data relating to symptoms were collected from patients upon referral with symptoms suspicious of lung cancer in two English regions; we also examined primary care and hospital records for diagnostic routes and diagnoses. Descriptive and regression analyses were used to investigate associations between symptoms and patient factors with diagnostic intervals and stage. RESULTS: Among 963 participants, 15.9% were diagnosed with primary lung cancer, 5.9% with other thoracic malignancies and 78.2% with non-malignant conditions. Only half the cohort had an isolated first symptom (475, 49.3%); synchronous first symptoms were common. Haemoptysis, reported by 21.6% of cases, was the only initial symptom associated with cancer. Diagnostic intervals were shorter for cancer than non-cancer diagnoses (91 vs 124 days, P=0.037) and for late-stage than early-stage cancer (106 vs 168 days, P=0.02). Chest/shoulder pain was the only first symptom with a shorter diagnostic interval for cancer compared with non-cancer diagnoses (P=0.003). CONCLUSIONS: Haemoptysis is the strongest symptom predictor of lung cancer but occurs in only a fifth of patients. Programmes for expediting earlier diagnosis need to focus on multiple symptoms and their evolution.

Development and validation of a robust specific enzyme mediated assay for phenylalanine in serum.

The specificity of a phenylalanine dehydrogenase, particularly with respect to cross reactivity toward tyrosine, has been shown to be pH dependent, being minimal at high pH. The dehydrogenase step has been coupled to colorimetric detection of NADH using a tetrazolium salt. The assay shows no significant cross reactivity towards a range of amino acids or drugs and correlates well with an established HPLC technique.

Development and validation of an automated enzyme assay for paracetamol (acetaminophen).

A rapid, enzymatic assay for serum or plasma paracetamol has been developed with the potential for adaptation to a wide range of clinical analysers. The method involves the action of an amidase enzyme to produce 4-aminophenol from paracetamol, which in turn reacts with 8-hydroxyquinoline in the presence of manganese ions to form a blue dye. Two stable reagents are used and excellent precision is achieved over the drug concentration range 0-2.5 mmol/l. The method, which is complete within 6 min, has been validated using a Monarch centrifugal analyser and shows no significant interference from endogenous serum compounds, drugs or paracetamol metabolites.

Studies on paracetamol binding to serum proteins.

There is a limited amount of data on the binding of paracetamol to plasma proteins. It has been suggested that binding might influence the ability of some analytical methods to quantify the total amount of drug present in the plasma fraction--the basis of clinical experience in risk assessment and antidote usage. We have investigated the binding of paracetamol to plasma proteins using an ultrafiltration technique. In overdose and spiked uraemic plasma samples the mean percentage of paracetamol bound was 24.1 (1SD = 7.0) with no significant correlation with drug levels or degree of uraemia. There is a small but significant increase in binding with increasing serum albumin concentration both in plasma (rs = 0.549, P = 0.014) and in pure serum albumin solutions (rs = 0.848, P < 0.001).

The benefits of rapid microbiological testing of finished products using ATP bioluminescence.

Microbiological quality control of personal care products using traditional methods can take between 5 and 7 days to complete. This is frequently the rate limiting step in product release. Companies are looking to improve manufacturing efficiencies and to maximize resources by releasing products faster. ATP bioluminescence has been shown to be applicable to the detection of low levels of contaminating organisms in a diverse range of personal care products including detergent-based and soap-based products, cosmetics and toothpastes. The system described here has demonstrated the detection of less than 10 colony forming units per sample of a range of typical contaminants in these product types after enrichment for 24 h.

A new biphasic minimal model.

Plasma insulin levels vary in an oscillatory fashion in both basal and postprandial states. The basic pattern is one of rapid (10 min) pulses superimposed on slower (50-100 min) oscillations. These oscillations increase after a glucose load and are altered in type 2 diabetes, impaired glucose tolerance or ageing. In response to a square-wave increase in interstitial glucose, beta-cells release insulin in a biphasic manner, with a sharp first phase lasting approximately 10 min followed by a gradually increasing release (second phase). Both phases are important for maintaining glucose homeostasis, but more emphasis has been placed on early insulin release because its attenuation causes glucose intolerance and late hyperinsulinemia. A new minimal model of glucose and insulin concentrations in plasma, which incorporates both the pulsatile and biphasic aspect of insulin production into existing minimal models, has been developed. The model is founded upon recent results on the action of beta-cells as fuel sensors and the dynamics of secretory granule exocytosis. The inclusion of a flexible model of insulin release is essential if the model is to be used to describe diabetic patients for more than a few hours and is a step towards a 24 hour free living model.

A rapid, enzymatic method for the determination of chloramphenicol in serum.

A simple, rapid assay of serum chloramphenicol has been developed which combines the specificity of the enzyme chloramphenicol acetyltransferase with the convenience of a colorimetric detection system. The assay is linear over the drug concentration range 5-200 microM (1.5-65 mg/l) and therefore is suitable for detection below and above the therapeutic range (31-62 microM, 10-20 mg/l with potential toxicity above 75 microM, 24 mg/l). This method does not detect the microbiologically inactive succinate or palmitate pro-drugs of chloramphenicol and evidence suggests that the major metabolite, chloramphenicol glucuronide also is not detected. Good correlation with an HPLC method has been achieved (r = 0.9860). The assay is based on a two reagent system with very simple methodology, the only instrumentation required being a spectrophotometer. However, the assay could be adapted to run on a range of discrete analysers.

The use of a layering technique for enhancing stability of lyophilized reagents.

An enzyme-mediated assay has been developed for the measurement of salicylate using salicylate monooxygenase purified from Pseudomonas cepacia ATCC 29351. Two assay formulations were produced, based on either a multiple-reagent or a single-reagent formulation, to allow sufficient flexibility for automated use. The multiple-reagent formulation was especially suited to diagnostic laboratories performing infrequent manual salicylate estimation where stability of the reconstituted reagent is of paramount importance. This was achieved by preparing the enzyme and color reagents in separate vials, so keeping the enzyme at a stable pH. For more frequent assay use where a reconstituted reagent shelf life was less important, the single-reagent system offers advantages of convenience. However, the working reagent required a pH of 10.0 upon reconstitution. Although the enzyme was sufficiently active at this pH to give a reliable assay, its storage stability was poor at pH 10.0, preventing lyophilization of the reagent at a pH suitable for immediate use on reconstitution. This incompatibility was overcome by use of a layering technique. The enzyme was separated from the buffering solution in the same vial by freezing the buffering solution and then overlayering with the enzyme reagent prior to a second freezing cycle and subsequent freeze drying.

Development and validation of an automated, enzyme-mediated colorimetric assay of salicylate in serum.

This salicylate-specific assay can be adapted for use with most discrete analyzers, for rapid emergency or routine testing with small serum or plasma sample volumes and a single calibration. The basis of this method is as follows: salicylate monooxygenase (EC 1.14.13.1) converts salicylate to catechol in the presence of NADH; the catechol then reacts with 4-aminophenazone under alkaline conditions, catalyzed by manganese ions, to produce a red dye. Incorporation of an NADH-regenerating system, involving glucose and glucose dehydrogenase, into the enzyme reagent ensures that the working reagent is stable for more than two weeks. The standard curve is linear over the drug concentration range 0 to 5 mmol/L. The CV was less than 4% over 20 days. Results correlated well with those by the Trinder colorimetric method and an HPLC method. We saw no interference by any of 80 drugs we tested at therapeutic concentrations or by endogenous compounds in serum.