Albert Huisman

Linking Laboratory and medication data: new opportunities for pharmacoepidemiological research

Abstract Transfer of automated laboratory data collected during routine clinical care from the laboratory information system into a database format that enables linkage to other administrative (e.g., patient characteristics) or clinical (e.g., medication, diagnoses, procedures) data provides a valuable tool for clinical epidemiological research. It allows the investigation of biochemical characteristics of diseases, therapeutic effects and diagnostic and/or prognostic markers for disease with easy access and at relatively low cost. To this end, the Utrecht Patient Oriented Database (UPOD), an infrastructure of relational databases comprising data on patient characteristics, laboratory test results, medication orders, hospital discharge diagnoses and medical procedures for all patients treated at the University Medical Centre Utrecht since January 2004, was established. Current research within UPOD is focused on the innovative linkage of laboratory and medication data, which, for example, makes it possible to assess the quality of pharmacotherapy in clinical practice, to investigate interference between laboratory tests and drugs, to study the risk of adverse drug reactions, and to develop diagnostic and prognostic markers or algorithms for adverse drug reactions. Although recently established, we believe that UPOD broadens the opportunities for clinical pharmacoepidemiological research and can contribute to patient care from a laboratory perspective. Clin Chem Lab Med 2007;45:13–9.

Anti-inflammatory effects of tetrahydrobiopterin on early rejection in renal allografts: modulation of inducible nitric oxide synthase.

Oxidative stress contributes to the development of early transplant failure. As nitric oxide synthases (NOS) can act as sources of superoxide, we investigated the effect of the NOS cofactor tetrahydrobiopterin (BH4) on oxyradical production and early rejection in a rat kidney transplantation model. Allograft transplantation (Brown Norway to Lewis) showed more renal superoxide production and monocyte infiltration when compared with isografts (Lewis to Lewis). Administration of the stable BH4 precursor sepiapterin had no effect on superoxide production in the isografts (51±10 vs. 69±17 cps/10 mg protein), but led to a marked decrease in superoxide production in the allografts (116±11 vs. 60±6 cps/10 mg protein; P<0.05) and was accompanied by a reduction in periarterial macrophage infiltration (3.3±0.7 vs. 1.3±0.3 cells/vessel; P<0.05) and an increase in NO production (78±22 vs. 173±12 AU/g kidney) (P<0.01). In vitro experiments confirm that iNOS can produce superoxide mainly from the heme domain, whereas BH4 administration can reverse this superoxide production in the presence of adequate anti‐oxidant defense. Our findings support the hypothesis that BH4 can be used to modulate the function of the inflammatory iNOS isoform and suggest a potential therapeutic role for sepiapterin in early allograft rejection.

Antioxidant capacity of mononitrosyl-iron-dithiocarbamate complexes: implications for NO trapping

Using EPR spectroscopy, we show that the water-soluble mononitrosyl iron complexes with N-methyl-D-glucamine dithiocarbamate (MNIC-MGD) ligands can easily react with superoxide and with peroxynitrite. The reaction with superoxide transforms the paramagnetic MNIC-MGD complex into an EPR silent complex with a reaction rate of 3 x 10(7) (M.s)(-1). Suppletion of ascorbate partially restores the complexes to their original paramagnetic state. We propose that the reaction of MNIC-MGD with either superoxide or peroxynitrite leads to identical EPR silent complexes. Our results have important implications for the technique of NO trapping in biosystems with Fe-dithiocarbamate complexes, where mononitrosyl-iron complexes (hydrophilic as well as hydrophobic) are formed as adducts in the trapping reaction. This principle is illustrated by NO trapping experiments on viable cultured endothelial cells. We find that MNIC-MGD acts as a very potent and water-soluble antioxidant with an efficiency exceeding most SOD mimics. Moreover, by accounting for the EPR silent fraction of iron complexes, the sensitivity of NO trapping can be enhanced considerably. The method was demonstrated for hydrophobic iron-dithiocarbamate complexes in endothelial cell cultures, where sensitivity for NO detection was enhanced by a factor of 5.

The state of point-of-care testing: a european perspective

Abstract Point-of-care testing (POCT) refers to any diagnostic test administered outside the central laboratory at or near the location of the patient. By performing the sample collection and data analysis steps in the same location POCT cuts down on transport and processing delays, resulting in the rapid feedback of test results to medical decision-makers. Over the past decades the availability and use of POCT have steadily increased in Europe and throughout the international community. However, concerns about overall utility and the reliability of benefits to patient care have impeded the growth of POCT in some areas. While there is no agreed-upon standard for how success should be judged, the increases in speed and mobility provided by POCT can lead to substantial advantages over traditional laboratory testing. When properly utilized, POCT has been shown to yield measurable improvements in patient care, workflow efficiency, and even provide significant financial benefits. However, important organizational and quality assurance challenges must be addressed with the implementation of POCT in any health care environment. To ensure maximal benefits it may be necessary to evaluate critically and restructure existing clinical pathways to capitalize better on the rapid test turnaround times provided by POCT.

Drug-induced thrombocytopenia: a population study.

AbstractBackground: Drug-induced immune thrombocytopenia, excluding heparin-induced thrombocytopenia, is a rare adverse drug reaction for which the evidence about frequency, relative risk and risk factors mainly originates from case reports and case studies. This study aims to quantify the risk for thrombocytopenia following exposure to drugs that are most often reported to cause thrombocytopenia in the general population. Methods: A retrospective, case-control study was conducted within the PHARMO record linkage system. Cases were defined as patients hospitalised for thrombocytopenia in the period 1 January 1990 to 31 December 2002. For each case, up to four controls were matched based on age, sex and geographical area. Exposure on the index date to anticonvulsants, β-lactam antibacterials, cinchona alkaloids, disease modifying antirheumatic drugs (DMARDs), diuretics, NSAIDs, sulfonamide antibacterials and tuberculostatics was assessed and categorised into mutually exclusive groups of current, recent, past and non-use. The risk was quantified with multivariate conditional logistic regression analysis. Results: The study population comprised 705 cases and 2658 controls. Current use of β-lactam antibacterials was associated with an increased risk for thrombocytopenia (adjusted odds ratio 7.4, 95% CI 1.8, 29.6). Increased risk estimates, although not significant, were found for current exposure to DMARDs and the sulfonamide antibacterial cotrimoxazole (trimethoprim/sulfamethoxazole). No increased risk was found for anticonvulsants, cinchona alkaloids, diuretics, NSAIDs or tuberculostatics. Conclusion: More evidence for an increased risk for thrombocytopenia in current use of β-lactam antibacterials in the general population was provided. The expected increase in risk could not be confirmed for the other drugs investigated, which is possibly a result of the limited statistical power. Future studies including more patients and with laboratory data should confirm our findings before drawing definite conclusions.

Optimisation of lupus anticoagulant tests: should test samples always be mixed with normal plasma?

Coagulation factor deficiencies are thought to interfere with the detection of the phospholipid-dependent coagulation inhibitor known as lupus anticoagulant (LA). Treatment with vitamin K antagonists (VKA) in particular, is thought to preclude accurate LA assessment. For this reason, the procedure to detect LA includes a mixing test, in which coagulation factor deficiencies are corrected by mixing samples with an equal volume of normal plasma. Despite these mixing tests, interpretation of LA test results is considered difficult in patients receiving high intensity VKA treatment. As a result, VKA treatment is often temporarily discontinued to allow LA assessment. However, whether coagulation factor deficiencies influence LA test results is unclear. We found that neither deficiency of a single coagulation factor, nor a functional coagulation factor deficiency due to high intensity VKA treatment, resulted in false positive dRVVT- or APTT-based (silica clotting time; SCT) LA test results. LA was readily detected in unmixed samples from VKA-treated LA-positive patients with both dRVVT and SCT reagents. VKA treatment caused an underestimation of the strength of the LA with SCT reagents, but did not lead to misclassification of LA status. Although mixing with normal plasma during both screen and confirm tests allowed more accurate assessment of the strength of the LA with SCT reagents in samples with an international normalised >2.5, the mixing procedure itself lead to misclassification of LA in weakly positive samples from patients not treated with VKA. Based on these findings, we conclude that mixing studies are not necessary during LA-assessment.

Atypical timing and presentation of periventricular haemorrhagic infarction in preterm infants: the role of thrombophilia

Aim  Periventricular haemorrhagic infarction (PVHI) is a complication of preterm birth associated with cardiorespiratory instability. To date, the role of thrombophilia as a possible additional risk factor in infants with atypical timing and presentation of PVHI has not been investigated.

Thrombocytopenia in adult cancer patients receiving cytotoxic chemotherapy: results from a retrospective hospital-based cohort study.

Background: Data on the frequency and relative risk (RR) of chemotherapy-induced thrombocytopenia (CIT) in patients with solid tumours receiving chemotherapy in clinical practice are limited.Objective: The aim of the study was to estimate the frequency and RR of thrombocytopenia in adult patients with solid tumours receiving chemotherapy treatment.Methods: For this retrospective, hospital-based study, adult patients with solid tumours who received chemotherapy at the University Medical Center Utrecht in the period 2004–6 were identified from the Utrecht Patient Oriented Database. We examined the frequency of (i) overall thrombocytopenia (defined as platelet count <100 × 109/L) with or without other cytopenias; (ii) isolated thrombocytopenia (i.e. without other cytopenias); and (iii) the frequency and RR of overall thrombocytopenia and isolated thrombocytopenia associated with different cytotoxic agents.Results: A total of 614 patients receiving one of 37 different chemotherapy regimens was included. Overall thrombocytopenia frequency was 21.8% and isolated thrombocytopenia frequency was 6.2%. The highest frequencies of thrombocytopenia were observed in patients receiving carboplatin monotherapy (81.8%) and combination therapies that included carboplatin (58.2%), gemcitabine (64.4%) or paclitaxel (59.3%). The highest RRs of thrombocytopenia, compared with cisplatin-based therapy, were observed for combination therapies of carboplatin/gemcitabine (RR 10.1; 95% CI 5.5, 18.5) and carboplatin/paclitaxel/etoposide (RR 11.8; 95% CI 6.7, 20.8). In 54% of cases, the thrombocytopenia was of grade 2–4, which are considered to be the most clinically relevant grades. The highest frequencies of isolated thrombocytopenia were found with combination therapies that included oxaliplatin (28.6%) or gemcitabine (28.9%).Conclusions: The results suggest that CIT is a relevant problem in clinical practice. Further research is necessary to investigate the clinical consequences of thrombocytopenia. The observed frequencies of thrombocytopenia were lower than those observed in older studies, but comparable with that observed in a recent US-based study. The observed increased risks for possible immune-mediated thrombocytopenia associated with exposure to oxaliplatin and gemcitabine contribute to the suspicion that these drugs can cause immune-mediated thrombocytopenia, and warrant further investigation. For clinicians, the mechanism has important consequences because in immune-mediated thrombocytopenia the drug must be avoided, while in dose-dependent thrombocytopenia a dose reduction may be sufficient.

Evaluation of hematological parameters on admission for the prediction of 7-day in-hospital mortality in a large trauma cohort

Abstract Background: We evaluated the complete blood count (CBC) for the prediction of 7-day in-hospital mortality in a large adult trauma cohort. Methods: We conducted an analysis of two prospectively collected databases on 1673 patients aged ≥18 years admitted to a level I trauma center (2005–2007). Comparisons between survivors and non-survivors within 7 days after admission and between single and multiple trauma patients were made. Discriminative performance for 7-day in-hospital mortality was assessed using the area under the receiver operating characteristic curve (ROC). Logistic regression was used to identify independent prognostic factors for 7-day in-hospital mortality. Results: Comparison between survivors and non-survivors showed significant differences in white blood cell (WBC) count, absolute neutrophil count, segmented neutrophil count and most red blood cell (RBC) and platelet indices. Comparison between single and multiple trauma patients showed significant differences for WBC count and differential count and most RBC and platelet indices. Among the CBC parameters, RBC count (ROC=0.748), hemoglobin concentration (Hb) (ROC=0.734), hematocrit (Ht) (ROC=0.726), platelet count (PLT) (ROC=0.684) and plateletcrit (PCT) (ROC=0.696) showed the highest ROC. Using logistic regression we showed that RBC count, Hb, Ht, PLT and PCT were predictors of 7-day in-hospital mortality independently of patients age, injury severity and initial physiological state. Conclusions: Significant differences in CBC parameters were found between survivors and non-survivors and between patients with single and multiple trauma, but most of the CBC parameters demonstrated poor to moderate pre dictive ability for 7-day in-hospital mortality in adult trauma patients. Routine laboratory workup of trauma patients should be performed as treatment guidance. However, prognostic value of initial hematological parameters remains limited.

Compliance with Platelet Count Monitoring Recommendations and Management of Possible Heparin-Induced Thrombocytopenia in Hospitalized Patients Receiving Low-Molecular-Weight Heparin

Background: Summaries of product characteristics (SPCs) and clinical guideline recommendations are available for monitoring the platelet count for heparin-induced thrombocytopenia (HIT) in patients receiving low-molecular-weight heparin (LMWH). Testing for the presence of heparin-platelet factor 4 antibodies (HPF4-Ab) and starting alternative anticoagulation is recommended when HIT is suspected. Objective: To investigate the frequency of compliance with recommendations for platelet count monitoring and management of possible HIT in hospitalized patients receiving prophylaxis and treatment dosing of LMWH for at least 5 consecutive days. Methods: A retrospective cohort study within the Utrecht Patient Oriented Database (UPOD) was conducted. For all inpatients, all episodes of exposure to dalteparin or nadroparin for at least 5 consecutive days in 2004–2005 were selected. In 4 different nonexclusive groups of patients (all pts. receiving dalteparin, all pts. receiving nadroparin, surgical pts. with a prophylactic dose of either dalteparin or nadroparin, and pts. exposed to unfractionated heparin [UFH] within 100 days before receiving either dalteparin or nadroparin), compliance with recommendations for platelet count monitoring from SPCs and a clinical guideline was studied. The frequency of compliance with these recommendations was determined. In addition, it was determined whether patient and treatment characteristics were associated with regular platelet count monitoring. Finally, the frequency of testing for HPF4-Ab and the initiation of danaparoid treatment in patients with a drop of at least 50% in platelet count were investigated. Results: A total of 6804 patients, with 7770 episodes of LMWH treatment, were included in the analysis. The frequency of compliance with platelet count monitoring recommendations was 26.3% for all patients receiving dalteparin, 35.6% for all patients receiving nadroparin, 23.0% for surgical patients receiving prophylactic dosing of either dalteparin or nadroparin, and 41.5% for patients exposed to UFH within 100 days before the start of either dalteparin or nadroparin treatment. Regular platelet count monitoring was strongly positively associated with medical patients (relative risk [RR] 2.33), surgical patients (RR 2.03), critically ill patients (RR 2.60), and those with recent exposure to UFH (RR 2.19). The frequency of testing for HPF4-Ab was 5.4% and the initiation of alternative anticoagulation with danaparoid in patients with a 50% drop in platelet count was 0%. Conclusions: The results suggest that compliance with recommendations for platelet count monitoring and management of possible HIT is low at our institution. Policies and tools to improve compliance with recommended laboratory monitoring should be developed to secure the safe use of LMWH and other medications.