[Real change or natural fluctuation?] / Echte verandering of natuurlijke schommeling?

When monitoring patients over time, it may be difficult to distinguish 'real changes' from so-called 'natural fluctuations' when interpreting consecutive laboratory results. Consider a patient whose cholesterol level has decreased from a baseline 6.6 mmol/L to 6.1 mmol/L six months after receiving lifestyle advice. How likely is it that this is a 'real change', reflecting a lifestyle change, rather than random fluctuation? Physicians mostly rely on their intuition and clinical experience when interpreting changes in consecutive laboratory results. For inexperienced physicians, the lack of an easy reference for the interpretation of consecutive laboratory results can make decision-making challenging. We have developed the medical/educational smartphone app Labtracker+ that calculates the probability of a 'real change' between two consecutive laboratory results, using biological variation data from scientific literature and analytical precision that is achieved in contemporary laboratories. This approach may complement intuitive, experience-based interpretations of consecutive laboratory results.

Differential protein expression in serum of abdominal aortic aneurysm patients - a proteomic approach.

OBJECTIVE: The aim of the study is to investigate the differential expression of proteins in serum of abdominal aortic aneurysm (AAA) patients in relation to aneurysm size (D(max)) and progression. METHODS: Two-dimensional differential in-gel electrophoresis (2D-DIGE) together with tandem mass spectrometry (MS/MS) was used to analyse the serum proteome from patients with small (D(max) 30-54 mm) AAA, either stable (increase D(max) <5 mm year⁻¹; n = 8) or progressive (increase D(max) ≥5 mm year⁻¹; n = 8), and large (D(max) ≥ 55 mm; n = 8) AAA. The identified proteins were quantitatively validated in a larger population (n = 80). RESULTS: Several proteins were differentially expressed in serum of small stable, small progressive and large AAA. Three validated proteins (immunoglobulin G (IgG), α1-antitrypsin (α1-AT) and Factor XII activity) showed strong correlation with D(max). Size combined with either Factor XII activity or α1-antitrypsin had minimal effect on the prognostic value in predicting aneurysm progression compared with size alone (area under the curve (AUC), 0.85; 95% confidence interval (CI), 0.73-0.97; p < 0.001 and AUC, 0.85; 95% CI, 0.72-0.98; p < 0.001 vs. AUC, 0.83; 95% CI, 0.71-0.96; p < 0.001, respectively). CONCLUSION: The present study indicates that both Factor XII and α1-antitrypsin are found in increased amounts in the serum of patients with expanding AAA. However, combination of either Factor XII or α1-antitrypsin with aneurysm diameter had little effect on prediction of aneurysm progression versus diameter alone.

Three-dimensional flow-through protein platform.

We have developed a new protein microarray (ImmunoFlow Protein Platform, IFPP) that utilizes a porous nitrocellulose (NC) membrane with printed spots of capture probes. The sample is pumped actively through the NC membrane, to enhance binding efficiency and introduce stringency. Compared to protein microarrays assayed with the conventional incubation-shaking method the rate of binding is enhanced on the IFPP by at least a factor of 10, so that the total assay time can be reduced drastically without compromising sensitivity. Similarly, the sensitivity can be improved. We demonstrate the detection of 1 pM of C-reactive protein (CRP) in 70 microL of plasma within a total assay time of 7 min. The small sample and reagent volumes, combined with the speed of the assay, make our IFPP also well-suited for a point-of-care/near-patient setting. The potential clinical application of the IFPP is demonstrated by validating CRP detection both in human plasma and serum samples against standard clinical laboratory methods.

Release kinetics of intact and degraded troponin I and T after irreversible cell damage.

PURPOSE: We characterized the release kinetics of cardiac troponin I and T in relation to lactate dehydrogenase (LDH) from cardiomyocytes before and after the transition from reversible to irreversible cell damage. METHODS: Cardiomyocytes were exposed to mild metabolic inhibition (1 mmol/L sodium azide) to induce a necrotic cell death process that is characterized by a reversible (0-12 h) and irreversible phase (12-30 h). At various time intervals cells and media were collected and analyzed for LDH activity, intact cTnI and cTnT, and their degradation products. RESULTS: During the first 12 h of metabolic inhibition, cell viability was unchanged with no release of intact cTnI and cTnT nor their degradation products. Between 12 and 30 h of azide treatment, cardiomyocytes showed progressive cell death accompanied by release of intact cTnI (29 kDa), intact cTnT (39 kDa), four cTnI degradation products of 26, 20, 17 and 12 kDa, and three cTnT degradation products of 37, 27 and 14 kDa. Possibly due to degradation, there is progressive loss of cTnI and cTnT protein that is obviously undetected by the antibodies used. CONCLUSIONS: Metabolic inhibition of cardiomyocytes induces a parallel release of intact cTnI and cTnT and their degradation products, starting only after onset of irreversible cardiomyocyte damage.

C-reactive protein, atherosclerosis and kidney function in hypertensive patients.

Previous studies have shown a relationship between coronary or carotid atherosclerosis and C-reactive protein (CRP) concentrations. In the present investigation, we evaluated the relationship between high-sensitivity CRP (hsCRP) concentrations and the presence of atherosclerotic lesions in the renal arteries and/or abdominal aorta. In 95 hypertensive patients who underwent intra-arterial DSA on suspicion of renovascular disease, blood was sampled during the procedure for measurement of hsCRP. The presence of atherosclerotic lesions was assessed at the level of the renal arteries and the abdominal aorta. Haemodynamically significant renal artery stenosis was diagnosed when 50% or more stenosis was observed. Patients with fibromuscular disease (n = 8) or incomplete data (n = 4) were excluded from analysis. The results revealed that the median hsCRP concentrations were significantly higher among the 57 patients with atherosclerosis of the aorta and/or renal arteries compared to those in the 26 patients without any angiographic lesions (4.6 vs 1.7 mg/l; P < 0.005). Moreover, in patients with renal artery stenosis, levels of hsCRP were higher when the degree of stenosis exceeded 50%. However, the association between hsCRP and the presence of atherosclerosis appeared to be confounded by serum creatinine, creatinine clearance, age and gender. In the whole group a significant inverse relationship was found between creatinine clearance and hsCRP (P < 0.05). In conclusion, hsCRP concentrations are related to atherosclerotic lesions in the renal arteries and the abdominal aorta. While this supports the view that atherosclerotic renal artery stenosis is part of a systemic inflammatory vascular disease, increased concentrations of CRP may also coincide with decreased renal function.

The value of (NT-pro) BNP in the diagnosis, prognosis and treatment of congestive heart failure.

Congestive heart failure constitutes one of the major causes of morbidity and mortality in Western countries. However, it is often misdiagnosed and the validity of the diagnosis is often difficult to establish. The clinical signs are not very sensitive and symptoms are nonspecific. Secretion of natriuretic peptides is increased in situations of cardiac overload. Testing the levels of these peptides, especially BNP and NT-proBNP, appears to offer a significant advance in the diagnosis and treatment of heart failure. In this article we would like to discuss the value of natriuretic peptides in congestive heart failure and give a short review of the literature.

Continuous 48-h C1-inhibitor treatment, following reperfusion therapy, in patients with acute myocardial infarction.

AIMS: Complement inhibition by C1-inhibitor has been shown to reduce myocardial ischaemia-reperfusion injury in animal models. We therefore studied the effects of intravenous C1-inhibitor, following reperfusion therapy, in patients with acute myocardial infarction. METHODS AND RESULTS: C1-inhibitor therapy was started not earlier than 6h after acute myocardial infarction, in order to prevent interference with thrombolytic therapy. A loading dose of C1-inhibitor was followed by a continuous infusion for 48 h, using three escalating dosage schemes. Efficacy of complement inhibition was estimated from C4 activation fragments. Plasma concentrations of myocardial proteins were compared to values measured in matched control patients. In 22 patients, C1-inhibitor was well tolerated and drug-related adverse events were not observed. Target plasma levels of C1-inhibitor were reached, with values of 48.2 ml.kg(-1) for distribution space and 35.5h for the half-life time of C1-inhibitor. A dose-dependent reduction of C4 fragments was found P=0.005). In 13 patients who received early thrombolytic therapy, release of troponin T and creatine kinase-MB(mass) was reduced by 36% and 57%P =0.001), compared to 18 controls. CONCLUSION: Continuous 48-h treatment with C1-inhibitor provides safe and effective inhibition of complement activation after reperfused acute myocardial infarction and may reduce myocardial injury.

Effect of acute phase response on cumulative troponin T release.

UNLABELLED: We studied a possible effect of the extent of the acute phase response after acute myocardial infarction on the cumulative release of troponin T. The height of the acute phase response might influence the cumulative release of troponin T, bound to the myofibrillar structures of the heart, in a different way compared to the free cytoplasmic cardiac marker hydroxybutyrate dehydrogenase (EC 1.1.1.27). To investigate this, the cumulative amount of C-reactive protein in plasma, i.e. the quantified acute phase response, was related to the cumulative plasma release of hydroxybutyrate dehydrogenase (an established method for infarct sizing) on the one hand and to that of troponin T on the other hand. The study was performed in patients receiving (n=16) and in patients not receiving (n=6) thrombolytic therapy. Cumulative protein release was calculated using a two-compartment model for circulating proteins. CONCLUSIONS: The cumulative amount of plasma C-reactive protein is significantly higher in the patients not receiving thrombolytic therapy, as is in accordance with earlier studies. The cumulative amount of troponin T released is significantly related to the cumulated concentration of C-reactive protein, especially in patients not receiving thrombolytic therapy. The intensity of the acute phase response, estimated from cumulative plasma C-reactive protein response, has no effect on the relative proportions of troponin T and hydroxybutyrate dehydrogenase released into plasma.

Diagnostic value of BAL fluid cellular profile and enzymes in infectious pulmonary disorders.

Determination of the cellular profile of bronchoalveolar lavage fluid (BALF), lactate dehydrogenase (LDH) and alkaline phosphatase (ALP) appeared to be useful in monitoring pulmonary damage. The aim of this study was to investigate whether the cellular profile, LDH, its isoenzyme pattern and/or ALP in BALF are useful in the diagnostic work-up of patients with suspected pneumonia. The BALF specimens of 80 patients were studied. Group I consisted of patients with a pulmonary infection (n=33) and group II of patients without signs of a pulmonary infection (n=47). Differentiation between these two groups was based upon the results of microscopy and quantitative cultures. The absolute as well as relative numbers of polymorphonuclear neutrophils (PMNs) was significantly higher in group I compared to group II (p<0.0001). The absolute number of PMNs showed a sensitivity of predicting the correct group of 95.7% and a specificity of 84.8%. The LDH activity in BALF was significantly higher in group I than in group II (p<0.0001). The LDH4/LDH5 ratio in BALF was lower in group I compared to group II (p<0.0001) and appeared to be the best discriminator between the two groups with a sensitivity of 93.6% and a specificity of 93.9%. In conclusion, the number of polymorphonuclear neutrophils as well as the lactate dehydrogenase activity, particularly its isoenzymes, in bronchoalveolar lavage fluid appeared to be of potential practical value to distinguish between infectious and noninfectious pulmonary disorders.

Association of fatigue with an acute phase response in sarcoidosis.

The pathophysiological explanation for fatigue, one of the most common symptoms in sarcoidosis, still has to be elucidated. It was hypothesized that the presence of fatigue is associated with an acute phase response in sarcoidosis. A cross-sectional study was performed in 38 sarcoidosis patients. Resting energy expenditure (REE) was measured in the fasting state by indirect calorimetry using a ventilated hood and adjusted for fat-free mass (FFM). Patients with fatigue (n=25) also suffered more frequently from other symptoms, such as exercise intolerance (p=0.01), the need for sleep (p=0.02) and weight loss (p=0.01), compared to those without fatigue (n=13). However, no relationship was found between fatigue and serum angiotensin-converting enzyme (sACE) or lung function impairment. Patients with fatigue had higher levels of C-reactive protein (CRP) (11.4+/-6.8 microg x mL(-1), p<0.0001) and REE adjusted for FFM (33.0+/-3.7 kcal x kg FFM(-1), p<0.003) compared to those without fatigue (3.2+/-2.2 mg x mL(-1); 29.2+/-2.8 kcal x kg FF(-1)). Furthermore, REE/FFM was significantly related to CRP (r=0.54, p=0.001). This study confirms the presence of an acute phase response as indicated by metabolic derangements and a moderate increase in C-reactive protein levels in sarcoidosis, particularly in those patients with constitutional symptoms. Future studies should focus on the clinical relevance and therapeutic implications of these findings.

Relationship between enzymatic markers of pulmonary cell damage and cellular profile: a study in bronchoalveolar lavage fluid.

It has been suggested that alterations in bronchoalveolar lavage fluid (BALF) reflect pathologic changes in the lung. Cytoplasmatic enzymes such as lactate dehydrogenase (LDH), alkaline phosphatase (ALP), and LDH isoenzymes are recognized indicators of cell damage or death. The aim of this study was to determine whether there is a relation between the enzyme activity and the cell types present in BALF. Therefore, BALF samples obtained from patients with various pulmonary disorders were studied. Out of these samples a group with mainly polymorphonuclear neutrophils (PMNs; n = 15; Group I) and another with mainly alveolar macrophages (AMs; n = 10; Group II) were selected. Additionally, the value of analysis of lysed cells in BALF for assessment of LDH-isoenzyme patterns was examined. The cell-free fraction of BALF of Group II showed lower LDH and ALP activity compared to Group I. The LDH-isoenzyme pattern also differed, with the LDH3/LDH5 ratios being lower in all BALF samples with predominantly PMNs than in BALF samples with predominantly AMs. Lysis of the cells present in the BALF samples by sonication prior to LDH-isoenzyme analysis provided no additional information beyond that found by analysis of the cell-free BALF. In conclusion, determination of enzyme activity appears to be useful in monitoring pulmonary inflammation.

Enhanced preoperative C-reactive protein plasma levels as a risk factor for postoperative infections after cardiac surgery.

BACKGROUND: We examined the possible predictive role of preoperative C-reactive protein (CRP) levels for postoperative infections in patients who have cardiac operations. METHODS: CRP levels were determined on the day before the operation and on postoperative days 1 to 4 and 6 in 593 consecutive patients. Furthermore, we documented infectious disease-related data. RESULTS: Patients in whom an infection developed during the postoperative course (n = 87) had significantly higher CRP levels on the day before operation (17.8+/-3.9 mg/L compared with 7.7+/-0.7 mg/L; p<0.001) and on postoperative days 4 and 6. The incidence of postoperative infections was significantly higher in patients with increased preoperative CRP levels than in those with normal preoperative CRP levels (25.3% versus 11.2%, respectively; p<0.001). Furthermore, patients with higher preoperative CRP levels had a significantly longer postoperative hospital stay than those with normal preoperative CRP levels (10.8+/-1.2 days versus 7.8+/-0.3 days; p<0.001). Multivariate analysis, including classic risk factors and increased preoperative CRP levels, demonstrated that higher preoperative CRP was the most important variable predicting postoperative infection (odds ratio = 2.7; 95% confidence interval = 1.7 to 4.3; p<0.001). CONCLUSIONS: Patients with higher preoperative CRP levels are at increased risk for postoperative infections. Therefore, preoperative measurement of CRP might be a useful, predictive marker in risk stratification for postoperative infections in patients scheduled for cardiac operations.