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PubMed2003

Standards for adult immunization practices.

Since the Standards for Adult Immunization Practices were first published in 1990, healthcare researchers and providers have learned important lessons on how to better achieve and maintain high vaccination rates in adults. The success rate of childhood immunization far exceeds the success rate of adult immunization. Thus, information and practices that will produce higher success rates for adult vaccination are crucial, resulting in overall societal cost savings and substantial reductions in hospitalizations and deaths. The Standards, which were developed to encourage the best immunization practices, represent the collective efforts of more than 100 people from more than 60 organizations. The revised Standards are more comprehensive than the 1990 Standards and focus on the accessibility and availability of vaccines, proper assessment of patient vaccination status, opportunities for patient education, correct procedures for administering vaccines, implementation of strategies to improve vaccination rates, and partnerships with the community to reach target patient populations. The revised Standards are recommended for use by all healthcare professionals and all public and private sector organizations that provide immunizations for adults. All who are involved in adult immunization should strive to follow the Standards in order to create the same level of success achieved by childhood vaccination programs and to meet the Healthy People 2010 goals.

Adult↗

PubMed2003

[2003 update of Standards, Options and Recommandations for radiotherapy for patients with salivary gland malignant tumors (excluding lymphona, sarcoma and melanoma)].

CONTEXT: The "Standards, Options and Recommendations" (SOR) project, which started in 1993, is a collaboration between the Federation of French Cancer Centers (FNCLCC), the 20 French Regional Cancer Centers. and specialists from French public universities,general hospitals and private clinics. The main objective is the development of clinical practice guidelines to improve the quality of health care and the outcome of cancer patients. OBJECTIVES: To update clinical practice guidelines for the management of patients with salivary gland malignant tumors previously validated in 1997. These recommendations cover diagnosis, treatment and follow-up of patients with these tumors. METHODS: The methodology is based on a literature review and critical appraisal by a multidisciplinary group of experts who define the CPGs according to the definitions of the Standards, Options and Recommendations project. Once the guidelines have been defined, the document is submitted for review by independent reviewers. RESULTS: This article presents the updated clinical practice guidelines concerning irradiation of patient with salivary gland tumors. The main recommendations are: 3 dimensional conformal radiotherapy (with or without intensity modulation) or 2D irradiation can be used; for surgical complete resected patients, postoperative photon radiotherapy should not be used in case of low grade stage I and 11 tumors(standard, level of evidence B2) but should be used for high grade stage II, II and IV tumors and for low grade stage III and IV tumors(standard, level of evidence B2). Neutron therapy should not be used in all of these cases (standard, level of evidence D); for patients presenting an incomplete macroscopic or microscopic surgical residual disease, postoperative irradiation must be delivered(standard). Neutron or photon therapy can be either delivered (options); for non operable patients neutron or photon therapy can be either delivered (options, level of evidence B2); for unresectable tumors or in case of recurrent neoplasms, exclusive neutron therapy or surgical tumor reduction combined with postoperative photon beam irradiation can be proposed (options, level of evidence C).

Combined Modality Therapy↗

PubMed2003

Multivariate calibration standardization across instruments for the determination of glucose by Fourier transform near-infrared spectrometry.

The transfer of multivariate calibration models is investigated between a primary (A) and two secondary Fourier transform near-infrared (near-IR) spectrometers (B, C). The application studied in this work is the use of bands in the near-IR combination region of 5000-4000 cm(-)(1) to determine physiological levels of glucose in a buffered aqueous matrix containing varying levels of alanine, ascorbate, lactate, triacetin, and urea. The three spectrometers are used to measure 80 samples produced through a randomized experimental design that minimizes correlations between the component concentrations and between the concentrations of glucose and water. Direct standardization (DS), piecewise direct standardization (PDS), and guided model reoptimization (GMR) are evaluated for use in transferring partial least-squares calibration models developed with the spectra of 64 samples from the primary instrument to the prediction of glucose concentrations in 16 prediction samples measured with each secondary spectrometer. The three algorithms are evaluated as a function of the number of standardization samples used in transferring the calibration models. Performance criteria for judging the success of the calibration transfer are established as the standard error of prediction (SEP) for internal calibration models built with the spectra of the 64 calibration samples collected with each secondary spectrometer. These SEP values are 1.51 and 1.14 mM for spectrometers B and C, respectively. When calibration standardization is applied, the GMR algorithm is observed to outperform DS and PDS. With spectrometer C, the calibration transfer is highly successful, producing an SEP value of 1.07 mM. However, an SEP of 2.96 mM indicates unsuccessful calibration standardization with spectrometer B. This failure is attributed to differences in the variance structure of the spectra collected with spectrometers A and B. Diagnostic procedures are presented for use with the GMR algorithm that forecasts the successful calibration transfer with spectrometer C and the unsatisfactory results with spectrometer B.

Algorithms↗

PubMed2001

Potency estimation of recombinant factor VIII: effect of assay method and standard.

Large potency discrepancies between the chromogenic and one-stage clotting methods have been reported for patients' plasma samples following the infusion of recombinant factor VIII (rFVIII) concentrates. We have investigated the potency estimation of two different full-length rFVIII concentrates using both assay methods relative to both plasma and concentrate standards. Potencies by the chromogenic method were significantly higher (53% and 45%) than potencies by the one-stage clotting method when a plasma standard was used. In contrast, there was no significant potency difference between methods when a concentrate standard was used. Time-course studies into thrombin and activated factor X (FXa) generation, in modified clotting and chromogenic methods, respectively, revealed that the two rFVIII concentrates behaved very similarly to the concentrate standard, whereas the plasma standard showed slightly more rapid thrombin generation and markedly slower FXa generation. The different behaviour of rFVIII and plasma FVIII in the chromogenic method is proposed as the main cause of the methods-based potency discrepancy. The results support the use of a concentrate standard to measure rFVIII in post-infusion plasma.

Blood Coagulation Tests↗

PubMedDate not supplied

A comparison of methods for determining lead content in drinking water: a portable anodic stripping voltammetry instrument method versus the standard EPA 239.2 method.

Lead levels in drinking water were measured by the standard U.S. Environmental Protection Agency (EPA)-approved atomic absorption spectroscopy-graphite furnace Method 239.2 and compared with determinations made with a newly available portable anodic stripping voltammetry (PASV) instrument. A standard curve was prepared at 2, 5, 10, 15, 20, 25, and 30 microg/L of lead. PASV instrument readings were lower than standard EPA method values, with a mean difference and standard error (SE) of the mean between the two of 1.538+/-0.588 microg/L (n = 7, p = 0.040, significant at the 95% confidence interval [CI]). First-flush drinking water samples collected from 144 water fountains/coolers were preserved with nitric acid. Total lead content was tested twice for 29 EPA method samples and 54 PASV instrument samples to determine the variation within each method; results were not significant at the 95% CI. Total lead content was determined for 144 samples by both methods. PASV instrument readings were lower than standard EPA method values (mean difference and SE of the mean 0.630+/-0.206 microg/L; n = 144, p = 0.0027, significant at the 95% CI). Mean and standard deviation of the 144 samples for the EPA method and the PASV instrument were 6.5+/-11.8 microg/L and 5.9+/-11.6 microg/L, respectively. Means were below the action level for lead of 15 ppb (microg/L), but some values were above the action level (18 [13%] using the EPA method; 20 [14%] using the PASV instrument). Retesting by EPA method showed two false positive PASV values. Results indicate that in some field situations the PASV instrument may prove useful due to its relatively low price, small size, ease of use, and quick readings.

Electrochemistry↗

PubMed1994

Two-color multiparametric method for flow cytometric DNA analysis. Standardization of spectral compensation.

Spectral overlap of green fluorescence signals into the red detector (red-minus-green compensation) is one potential source of variation in two-color flow cytometric DNA analysis. Suboptimal compensation in a two-color propidium iodide (PI)/fluorescein isothiocyanate (FITC) system may be observed if compensation is adjusted using an inappropriate standard, or if changes to fluorescence detector high-voltage settings are made without corresponding readjustment of fluorescence compensation. To quantitate the influence of red-minus-green compensation on the quality of DNA histograms, data from 60 dual PI/cytokeratin (CK)-FITC stained carcinomas were acquired in parallel using two compensation standards: a PI/CK-FITC-stained T24 cell line calibrator overstained to achieve a high-intensity green fluorescence standard (HIGFS) with manually set compensation and automated compensation settings derived from commercial phycoerythrin/low intensity FITC beads (LIGF). Both compensation standards gave similar DNA hyperdiploidy results (DNA index, 1.1-2.8). However, LIGF standard yielded two falsely hypodiploid peaks (DNA index, .7 and .9). Eight left-skewed peaks became DNA diploid and symmetric, respectively, with the HIGFS. Use of HIGFS lowered the coefficient of variation percentage in 95% of cases, the greatest differences (maximum, 3.4%; mean, 1.81%) in tumors of highest intensity CK-FITC. The authors concluded that use of cell-based compensation standards (HIGFS) with intense green signals that mimic clinical tumor samples will avoid spurious aneuploidy and maximize resolution of near-diploid abnormalities.

Analysis of Variance↗

PubMed2000

Reactivity of different LH and FSH standards and preparations in the world health organization matched reagents for enzyme-linked immunoassays of gonadotrophins.

The immunoreactivity of various LH and FSH calibration standards and recombinant preparations in the enzyme-linked immunoassay (EIA) systems for gonadotrophins developed for the Special Programme of Research in Human Reproduction of the World Health Organization (WHO) were compared. The preparations tested included three LH and two FSH pituitary standards (calibrated against LH 80/552 and 68/40 and FSH 78/549 respectively) provided with the EIA or radioimmunoassay WHO matched reagent kits, the pituitary preparation LER-907, and recombinant human LH (rhLH) and FSH (rhFSH). Simultaneous curve fitting of the EIA dose-response curves revealed no significant differences among the slopes generated by the WHO LH standards and LER-907; in contrast, no parallelism was found between the curves of rhLH and the pituitary-derived LH standards. No significant differences were found among the slopes of the curves elicited by the pituitary and recombinant FSH preparations. Each LH preparation exhibited a high degree of charge heterogeneity. Considerable variations in charge isoform distribution among the WHO LH standards, rhLH and LER-907 were also evident. In contrast, the FSH preparations were less heterogeneous and exhibited minor differences in charge distribution. Despite the existing differences in charge isoform distribution, all the pituitary-derived preparations as well as rhFSH seem appropriate for using as calibration standards in this particular EIA system.

Animals↗

PubMed1996

Standardization of antifungal susceptibility testing.

The application of in-vitro antifungal susceptibility testing to clinical research and to the guidance of antifungal therapy has been limited by a lack of reproducibility and uncertain clinical relevance. As a result of studies of the identified variables impacting on in-vitro susceptibility results, the National Committee for Clinical Laboratory Standards have proposed a standardized antifungal susceptibility test method M27-P. The degree of intra- and inter-laboratory reproducibility which can be achieved with this method have been defined in multi-laboratory collaborative studies. More convenient methods (microdilution broth and stable gradient technology) have been evaluated relative to the proposed standard method and the potential for a similar process with a disc diffusion method is apparent. A modification of this standard method for susceptibility testing of filamentous fungi appears promising. The existence of a standardized method and of alternative methods with a defined relationship to the proposed standard, facilitates meaningful analysis of published studies addressing the issue of clinical relevance of antifungal susceptibility testing. As a result of this process, correlation of MICs determined in vitro with clinical response to therapy is beginning to emerge, most notably in relation to fluconazole therapy for oropharyngeal candidosis associated with infection with the human immunodeficiency virus.

Antifungal Agents↗

PubMed2006

Before-after study of a standardized hospital order set for the management of septic shock.

OBJECTIVE: To evaluate a standardized hospital order set for the management of septic shock in the emergency department. DESIGN: Before-after study design with prospective consecutive data collection. SETTING: Emergency department of a 1,200-bed academic medical center. PATIENTS: A total of 120 patients with septic shock. INTERVENTIONS: Implementation of a standardized hospital order set for the management of septic shock. MEASUREMENTS AND MAIN RESULTS: A total of 120 consecutive patients with septic shock were identified. Sixty patients (50.0%) were managed before the implementation of the standardized order set, constituting the before group, and 60 (50.0%) were evaluated after the implementation of the standardized order set, making up the after group. Demographic variables and severity of illness measured by the Acute Physiology and Chronic Health Evaluation II were similar for both groups. Patients in the after group received statistically more intravenous fluids while in the emergency department (2825 +/- 1624 mL vs. 3789 +/- 1730 mL, p = .002), were more likely to receive intravenous fluids of >20 mL/kg body weight before vasopressor administration (58.3% vs. 88.3%, p < .001), and were more likely to be treated with an appropriate initial antimicrobial regimen (71.7% vs. 86.7%, p = .043) compared with patients in the before group. Patients in the after group were less likely to require vasopressor administration at the time of transfer to the intensive care unit (100.0% vs. 71.7%, p < .001), had a shorter hospital length of stay (12.1 +/- 9.2 days vs. 8.9 +/- 7.2 days, p = .038), and a lower risk for 28-day mortality (48.3% vs. 30.0%, p = .040). CONCLUSIONS: Our study found that the implementation of a standardized order set for the management of septic shock in the emergency department was associated with statistically more rigorous fluid resuscitation of patients, greater administration of appropriate initial antibiotic treatment, and a lower 28-day mortality. These data suggest that the use of standardized order sets for the management of septic shock should be routinely employed.

Adult↗

PubMed2004

Collaborative field study on the utility of a BDD factor VIII concentrate standard in the estimation of BDDr Factor VIII:C activity in hemophilic plasma using one-stage clotting assays.

Advances in production technologies of factor (F)VIII concentrates during the last two decades has resulted in very pure and safe products. In assessment of recombinant FVIII:C, inconsistent assay values are found comparing one-stage assays with two-stage (e.g. amidolytic) methods. Such discrepancies have been quite prominent in the case of a B-domain deleted recombinant FVIII (BDDrFVIII, ReFacto). In order to alleviate this assay variance, a product-specific reference standard [the ReFacto Laboratory Standard (RLS)], was established for laboratory use with either one-stage clotting or chromogenic substrate assays for the measurement of FVIII:C in ReFacto-containing patient samples. The primary objective of the current study was to assess, under field laboratory conditions, the accuracy and precision of the one-stage clotting assay for the determination of FVIII:C in ReFacto-containing samples employing the new concentrate standard. A secondary goal was to assess whether use of the RLS would minimize the discrepancy between one-stage clotting and chromogenic substrate assays. Thirty-one clinical laboratories worldwide participated in the study of severe-hemophilic plasma (SHP) samples that had been spiked with ReFacto to target levels of 0.9, 0.6 and 0.2 IU mL(-1). FVIII:C levels were determined against both the RLS and the local in-house plasma standard (IHS). The results showed good agreement between laboratories in FVIII:C levels obtained by one-stage clotting assays utilizing the RLS, and a good degree of accuracy was found compared with the intended target values. Consistent with previously published data, a discrepancy of approximately 30% was observed between one-stage clotting and chromogenic potencies when the IHS was used as the calibrator. The discrepancy between one-stage and chromogenic assay methodologies was significantly reduced when the RLS was employed as calibrator in the one-stage assay. In conclusion, the study demonstrates that accurate and precise FVIII:C results can be obtained for ReFacto-containing SHP samples by clinical laboratories using a product-specific standard in one-stage clotting assays. In addition, the product-specific reference standard significantly reduced the discrepancy between the one-stage clotting and the chromogenic substrate assay for ReFacto.

Blood Coagulation↗

PubMed2025

Unveiling the inequivalent biochemical functions of OsSMO2-1 and OsSMO2-2 in rice phytosterol biosynthesis using a customized sterol standards mixture.

Phytosterols, natural active components widely distributed in plants, commonly include β-sitosterol, stigmasterol, and campesterol. However, identifying their synthesis intermediates can be challenging because access to corresponding commercial standard compounds is not always possible. To overcome these limitations, we synthesized phytosterol intermediates by co-infecting Nicotiana benthamiana with verified phytosterol synthases and identified them via gas chromatography-mass spectrometry analysis. Then, we mixed the identified intermediates, re-analyzed them by GC-MS to get a customized standard mixture, and established the corresponding standard spectrum library and characteristic ion database. To prove the usability of this standard mixture, we analyzed sterol intermediate types and contents in OsSMO2-1 and OsSMO2-2 rice mutants with this tool. Using the standard mixture, we analyzed sterolomics in wild-type rice buds at different germination days. As buds grew, detectable sterol intermediates decreased; only campesterol, sitosterol, and stigmasterol were found at the 9-day-old bud. When we compared mutants (ossmo2-1/ossmo2-2) with the wild type, we noted an obvious peak of 24-ethylidenelophenol accumulation in the ossmo2-1 mutant, indicating non-equivalent functions of OsSMO2-1 and OsSMO2-2 in sterol synthesis. OsSMO2-1 is more crucial for stigmasterol and sitosterol synthesis. This validates the standard mixture's utility.

Oryza↗

PubMed2005

Mitral repair best practice: proposed standards.

OBJECTIVES: To define best practice standards for mitral valve repair surgery. DESIGN: Development of standards for process and outcome by consensus. SETTING: Multidisciplinary panel of surgeons, anaesthetists, and cardiologists with interests and expertise in caring for patients with severe mitral regurgitation. MAIN OUTCOME MEASURES: Standards for best practice were defined including the full spectrum of multidisciplinary aspects of care. RESULTS: 19 criteria for best practice were defined including recommendations on surgical training, intraoperative transoesophageal echocardiography, surgery for atrial fibrillation, audit, and cardiology and imaging issues. CONCLUSIONS: Standards for best practice in mitral valve repair were defined by multidisciplinary consensus. This study gives centres undertaking mitral valve repair an opportunity to benchmark their care against agreed standards that are challenging but achievable. Working towards these standards should act as a stimulus towards improvements in care.

Atrial Fibrillation↗

PubMedDate not supplied

Why is the standardization of prothrombin time a problem?

The standardization of prothrombin time (PT) has been a problem for more than 50 years; by applying the methods to the same clinical material the analysis may explain why. The initial standardization by 2--3 times normal clotting time by Quick's PT assay did not standardize presently used PT assays. The ratio method accepted by the WHO in 1977 was not satisfactory because the intercept was neglected. The revised ratio method (WHO 1983) recommended calibration between log clotting times of normal and abnormal plasmas and a simplified conversion into ratios. However, by including a high proportion of normal plasmas (up to 1/3 of abnormal) an erroneous calibration material was introduced; the conversion from clotting times into ratios was also more complex than predicted. The international sensitivity index, which is based on the simplified method, produced international normalized ratios (INR) that were not more standardized than not corrected ratios. Not corrected coagulation activities showed poor standardization due to the different sensitivity of assays for the protein induced by vitamin K absence (Pivka) inhibitor. The corresponding therapeutic ranges of INR and coagulation activities covered 70 and 10--20% of their scales, respectively. Standardization by Pivka-corrected coagulation activities against an international reference assay may be the preferable method.

Blood Coagulation Tests↗

PubMed1988

Validity of the newly established low-molecular-weight heparin standard in cross-referencing low-molecular-weight heparins.

Four low-molecular-weight-heparin (LMWH) preparations have recently become available for clinical usage. Some ten preparations are currently under preclinical development. The safety/efficacy profile of each of these LMWHs is now known to be quite distinct from one and other. In order to minimize the variations in the pharmacologic responses and to cross-reference different products on a common scale, the WHO has recently introduced a LMWH standard. This standard is a nitrous-acid-depolymerized product provided by KabiVitrum (Stockholm, Sweden) with a specific physiochemical and biological profile. Although the in vitro characteristics of this standard are comparable to other LMWH, the in vivo behavior of this reference and the parent product, Fragmin, are quite different in comparison to other products. In a well-defined uniform biochemical and pharmacologic screening, seven LMWH were compared at WHO reference-adjusted potency using pharmacologically valid dose-response curves. Cross-referencing of various LMWHs against the WHO standard in terms of anti-Xa activity resulted in a marked elevation of the anti-IIa component of some of the LMWHs. Establishment of this WHO standard stipulated that the clinical performance of cross-referenced LMWHs would be equivalent to one another and variation in potency could be minimized. Our data suggest that utilizing the WHO, standard individual potency (anti-Xa)-adjusted LMWHs exhibit distinct safety/efficacy profiles which were not related in their observed in vitro potency. Each LMWH has distinct multiparametric molecular and biochemical characteristics which determine the pharmacologic activities of individual agents. Thus cross-referencing of LMWHs by one in vitro assay is of questionable value as it may result in serious dosimetric errors, resulting in serious thrombotic and bleeding complications.

Animals↗

PubMed2006

Standard setting: comparison of two methods.

BACKGROUND: The outcome of assessments is determined by the standard-setting method used. There is a wide range of standard-setting methods and the two used most extensively in undergraduate medical education in the UK are the norm-reference and the criterion-reference methods. The aims of the study were to compare these two standard-setting methods for a multiple-choice question examination and to estimate the test-retest and inter-rater reliability of the modified Angoff method. METHODS: The norm-reference method of standard-setting (mean minus 1 SD) was applied to the 'raw' scores of 78 4th-year medical students on a multiple-choice examination (MCQ). Two panels of raters also set the standard using the modified Angoff method for the same multiple-choice question paper on two occasions (6 months apart). We compared the pass/fail rates derived from the norm reference and the Angoff methods and also assessed the test-retest and inter-rater reliability of the modified Angoff method. RESULTS: The pass rate with the norm-reference method was 85% (66/78) and that by the Angoff method was 100% (78 out of 78). The percentage agreement between Angoff method and norm-reference was 78% (95% CI 69% - 87%). The modified Angoff method had an inter-rater reliability of 0.81-0.82 and a test-retest reliability of 0.59-0.74. CONCLUSION: There were significant differences in the outcomes of these two standard-setting methods, as shown by the difference in the proportion of candidates that passed and failed the assessment. The modified Angoff method was found to have good inter-rater reliability and moderate test-retest reliability.

Clinical Competence↗

PubMed1989

Chromogenic endotoxin assay in plasma. Selection of plasma pretreatment and production of standard curves.

The aim of this study was to define the optimal conditions for the plasma pretreatment and to improve the production of standard curves for plasma endotoxin determination by a chromogenic substrate assay. Endotoxin standard from E. coli O 111:B 4 (0-50 ng/l) was added to pyrogen-free water or to plasma samples from 12 healthy subjects and 24 alcoholics, before pretreatment by heating (75 degrees C, 5 minutes) or with perchloric acid (0.32 mol/l). When endotoxin standard curves were determined using a microprocessor-controlled reader, the slopes of the curves obtained with plasma differed from those with pyrogen-free water. The slope of the standard curve prepared with plasma samples from different patients exhibited marked interindividual variations. Compared with the heating method, the perchloric acid method gave more variable results and a lower recovery of added endotoxin, especially in plasma from alcoholics. The results permit the following conclusion: 1. For plasma endotoxin determination, a standard curve should be prepared for each individual plasma sample. 2. The endotoxin standard should be added before pretreatment of the plasma. 3. Pretreatment of the plasma by heating at 75 degrees C for 5 minutes provides more reliable results than pretreatment with perchloric acid.

Adult↗

PubMed1987

Developing and implementing standards of practice for clinical pharmacy services.

The authors' department has attempted to bring more order to the provision and evaluation of clinical services through the development of "Clinical Standards of Practice." A pilot project was initially conducted on one satellite. Pharmacists were asked to prepare a list of minimum standards that could be agreed upon and that everyone believed were achievable even on the busiest days. After standards were developed and implemented, a procedure was established to evaluate compliance through review of pharmacy records and patient materials. Staff received feedback concerning the results of the review. As a result of the success with the pilot, Clinical Standards of Practice have been developed by staff and are in use throughout the department. Plans for the future include continuous revision of the standards to reflect changing departmental goals and directions and a change to a "pharmacist specific" rather than a current "nursing unit specific" monthly review format to facilitate performance review and staff development. Eleven standards are shown in the appendices.

Clinical Competence↗

PubMed1999

Standardization of coagulation tests.

A lot of attempts have been made to standardise both activated partial thromboplastin time (APTT) and prothrombin time (PT). Only the standardization of PT has been successfully implemented while the standardization of APTT is still underway. The PT test is a common method for monitoring oral anticoagulant therapy. Owing to the variable response of the thromboplastins and the different ways of reporting, PT results obtained from patients treated with oral anticoagulants have not been interchangeable between laboratories. In 1977, the World Health Organization (WHO) designed a batch of human brain thromboplastin as the first international reference preparation (IRP) for thromboplastin and a calibration system was proposed in 1982, based on the assumption that a linear relationship exists between the logarithm of the PT obtained with the IRP and test thromboplastins. This calibration model is used to standardize the reporting of the PT by converting the PT ratio observed with the local thromboplastin into an International Normalized Ratio (INR). The INR system is being adopted by an increasing number of hospitals in many countries. With the increasing use of the INR system, a number of problems have been identified with the INR system. The most serious one is that the ISI of a thromboplastin depends on the coagulometer used. Besides, a number of investigators have noted that the ISI value provided by the manufacturer for each new batch of thromboplastin reagent may be incorrect and the use of inappropriate control plasma can lead to erroneous INR calculations. Four solutions have been proposed to solve the problems of the INR system as follows: (a) the local system calibration with lyophilized plasma calibrants with assigned manual PT determined in terms of the relevant IRP for thromboplastin; (b) the use of a mean normal prothrombin time (MNPT) obtained with the coagulometer to derive the prothrombin ratio: (c) PT standardization by means of the procedure using plasma calibrants: and (d) selection of sensitive thromboplastin with low ISI values. The INR system has been adopted in Thailand since 1984. There are 3 steps in the implementation as follows: (a) preparation of National Reference Thromboplastin; (b) selection of high sensitive thromboplastin; and (c) optimal therapeutic range for Thai patients. The anticoagulant effect of heparin is usually monitored by the APTT, a test that is sensitive to the inhibitory effects of heparin on thrombin, factor Xa. and factor IXa. However, the type of clot detection system, the contact activator; and the phospholipid composition of the reagent affect the APTT response. In 1995. ISTH/ICSH proposed a calibration model for APTT standardization. As the problem showed a great similarity to PT standardization, the same model of calibration was applied but no international reference preparation for the APTT is yet available. In 1998. van den Besselaar et al proposed a lyophilized APTT reagent comprising synthetic phospholipids and colloidal silica as a candidate IRP for the APTT.

Anticoagulants↗