Westergren tubes for measurement of erythrocyte sedimentation rate

Transcription

1 INTERNATIONAL OIML R 78 RECOMMENDATION Edition 1989 (E) Westergren tubes for measurement of erythrocyte sedimentation rate Pipettes Westergren pour la mesure de la vitesse de sédimentation des hématies OIML R 78 Edition 1989 (E) ORGANISATION INTERNATIONALE DE MÉTROLOGIE LÉGALE INTERNATIONAL ORGANIZATION OF LEGAL METROLOGY

2 Foreword The International Organization of Legal Metrology (OIML) is a worldwide, intergovernmental organization whose primary aim is to harmonize the regulations and metrological controls applied by the national metrological services, or related organizations, of its Member States. The two main categories of OIML publications are: International Recommendations (OIML R), which are model regulations that establish the metrological characteristics required of certain measuring instruments and which specify methods and equipment for checking their conformity; the OIML Member States shall implement these Recommendations to the greatest possible extent; International Documents (OIML D), which are informative in nature and intended to improve the work of the metrological services. OIML Draft Recommendations and Documents are developed by technical committees or subcommittees which are formed by the Member States. Certain international and regional institutions also participate on a consultation basis. Cooperative agreements are established between OIML and certain institutions, such as ISO and IEC, with the objective of avoiding contradictory requirements; consequently, manufacturers and users of measuring instruments, test laboratories, etc. may apply simultaneously OIML publications and those of other institutions. International Recommendations and International Documents are published in French (F) and English (E) and are subject to periodic revision. This publication reference OIML R 78 (E), edition 1989 which is under the responsibility of TC 18/SC 5 Measuring instruments for medical laboratories, was sanctionned by the International Conference of Legal Metrology in OIML publications may be obtained from the Organization s headquarters: Bureau International de Métrologie Légale 11, rue Turgot Paris - France Telephone: 33 (0) and Fax: 33 (0) biml@oiml.org Internet: 2

3 WESTERGREN TUBES for MEASUREMENT of ERYTHROCYTE SEDIMENTATION RATE 1. Scope This International Recommendation applies to Westergren tubes used to determine the sedimentation rate of erythrocytes in human blood containing an anti-coagulant. 2. Scale 2.1. Tubes for the measurement of blood sedimentation rate shall bear a scale graduated in millimetres The zero scale mark shall be 200 mm from the tip of the tube The scale shall extend at least to the 180 mm graduation line, but shall not extend beyond the cylindrical part of the exterior of the tube The graduation lines shall lie in planes at right angles to the longitudinal axis of the tube The graduation lines shall be clear, easy to distinguish, of uniform width and indelible under normal conditions of use. They shall withstand cleaning The width of the graduation lines shall not exceed 0.3 mm The length of the graduation lines shall be : Short graduation lines Medium graduation lines Long graduation lines : at least 2.5 mm : at least 4.0 mm : at least 6.0 mm The arrangement of the graduation lines shall be : Long graduation lines : 0 mm 10 mm 20 mm etc. Medium graduation lines : 5 mm 15 mm 25 mm etc. Short graduation lines : all other graduation lines Scale numbering The scale shall be numbered from top to bottom Every 10th or every 20th graduation line shall be numbered Each number shall be clearly associated with its corresponding graduation line. 3. Material The Westergren tubes shall be made of glass or of plastic material, transparent, free from defects liable to prevent correct use of the instruments and reasonably free from internal stress. 3

4 4. Manufacturing requirements 4.1. The dimensions shall be as follows : Total length of the tube : mm Inside diameter of the tube : 2.55 mm (from the tip of the tube to 20 mm above the zero scale mark) The tip of the tube shall be conical outside. The length of the tapered portion of the tube shall be 4 mm to 8 mm. The wall tickness of the orifice shall be at least 0.5 mm. 5. Markings 5.1. The symbol "mm" shall be placed close to the zero scale mark The word " Westergren " shall be inscribed adjacent to the scale. 6. Maximum permissible errors 6.1. The maximum permissible errors on verification are as follows : Inside diameter ± 0.15 mm Distance between the zero scale mark and the tip of the tube ± 0.4 mm Distance between the centers of adjacent long graduation lines, of adjacent medium graduation lines and of adjacent short graduation lines ± 0.2 mm Difference between the lengths of adjacent scale divisions ± 0.2 mm Total length of tube ± 0.5 mm 6.2. The maximum permissible errors in service are the same as those on verification. 7. Space for the official mark A clear space for the official mark shall be provided. 8. Test procedure 8.1. The inside diameter of the tube shall be measured with vernier callipers or verified with cylindrical plug gauges having maximum permissible errors of 0.05 mm. The overall length of the tube and the distance between the centres of the graduations shall be measured using a simple comparator with a maximum permissible error of 0.05 mm The permanence of the graduation lines after cleaning shall be verified by the following test. A chromic-acid cleaning solution shall be freshly prepared by dissolving 200 g of sodium dichromate in ml of distilled water and ml of reagent-grade sulphuric acid. The tube shall be immersed in the chromic acid solution for 15 minutes at ambient temperature between 20 C and 25 C. After removal from the acid bath the tube shall be thoroughly rinsed in distilled water and dried by 5 to 10 vigourous strokes of a laboratory cloth or tissue. The appearance of the graduation lines, as judged by the eye under normal room lighting, shall remain unchanged as a result of the test. 4

5 Contents Foreword Scope Scale Material Manufacturing requirements Markings Maximum permissible errors Space for the official mark Test procedure