The following is a list of the apparatus needed to equip a laboratory capable of carrying out all the examinations described in this manual. Such a laboratory would usually be located in a small rural hospital (district level) which might have be- tween 60 and 100 beds.
1. Essential laboratory instruments
Microscopes
The laboratory should be equipped with two microscopes.
● One microscope is for use in haematology. It should have an inclined binocular tube, a mechanical stage, three objectives (x 10, x 40, x 100), two eyepieces (x 5,x 10), a condenser and an electric lamp that can be connected to the mains electricity supply or a battery.
● The second microscope is for use in other laboratory procedures (parasitology, urine analysis, bacteriology, etc.) and should have an inclined binocular tube and accessories as listed above.
At the health centre level one binocular microscope is sufficient.
Centrifuges
It is useful to have two centrifuges:
— an electric centrifuge with a microhaematocrit head attachment and a reader;
— a hand-operated or an electric centrifuge with four buckets.
Balance
An analytical balance with a set of weights is necessary if reagents are to be pre- pared in the laboratory.
If the laboratory is required to prepare a wide range of reagents, a two-pan balance with a corresponding set of weights (see section 3.2.2) is useful.
Refrigerator
Reagents (such as those required for pregnancy tests, etc.) and materials (such as certain transport media, specimens, etc.) should be kept in the refrigerator.
Water-bath
A water-bath equipped with a thermostat for temperature control is required when samples or materials must be kept at a certain temperature and when measure- ments must be made at a given temperature.
Differential counter
Although a hand tally counter can be used, a differential counter saves time.
Photometer or colorimeter
2. Additional items
Autoclave
If the laboratory is in a hospital, the hospital sterilization service can be used. If the laboratory is in a health centre one of the following is needed (see section 3.5.5):
— a small autoclave (electric or heated by an oil stove or with butane gas)
— a pressure cooker.
Hot-air oven
If the laboratory is fairly large, a small hot-air oven is useful for drying glassware and for sterilization in conjunction with the autoclave (see section 3.5.5).
Deionizer or water still
A deionizer is an apparatus for demineralizing water by means of cartridges filled with ion-exchange resin (see section 2.4.3).
If a deionizer is not available, a water still can be used (see page 25).
3. Equipment and supplies
A list of equipment and supplies for a peripheral-level health laboratory is given in Table 2.2. The quantities proposed are sufficient to enable a laboratory with one or two technicians to perform 20–50 examinations per day for a period of 6 months. Glassware and small items of equipment for laboratory use are shown in Fig. 2.40.
4. king glass equipment
Glass is produced by the fusion at a very high temperature of sand and potassium (or sodium). This forms a silicate (ordinary soda-lime glass). Sometimes boric acid is added to the ingredients to produce borosilicate glass, which is less brittle and more resistant to heat than ordinary glass. Certain pieces of equipment can be made in the medical laboratory by heating ordinary glass.
Materials
● Hollow glass tubing with an external diameter of 4–8 mm and 0.9–1.0 mm thick
● Glass rods with a diameter of 4–8 mm
● File, glass cutter or diamond pencil
● Cloth
● Bunsen burner (or a small gas or petrol blowlamp).
Making a Pasteur pipette
1. Take a piece of glass tubing 4–6 mm in diameter. Using the file, mark off the required lengths of tubing:
— 14–15 cm for small pipettes;
— 18–25 cm for large pipettes.
Etch the mark right round the tube, forming a circle (Fig. 2.41).
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Fig. 2.40 Glassware and equipment for laboratory use
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 Table 2.2 Equipment and
supplies for a peripheral-level health laboratory |
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| Table 2.2 Equipment and supplies for a peripheral-level health laboratory |
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| Fig. 2.41 Marking off the required length of glass tubing using a file |
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Fig. 2.42 Breaking the glass
tubing by hand
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| Fig. 2.43 Rounding off the ends of the glass tubing by flaming |
2. Wrap the part to be broken in a cloth. Hold the tube with both hands, one thumb on either side of the etched mark (Fig. 2.42). Snap by pressing with your thumbs.
3. Round off the end of each piece of tubing as shown in Fig. 2.43:
— heat the end, holding the tube almost vertical just above the blue flame of the burner;
— keep turning slowly;
— stop when the glass becomes red hot.
4. Stand the tubes in a beaker or a can, heated ends up, and leave to cool.
Wash all the pieces of tubing prepared (following the instructions given in section 3.5.1). Rinse and dry.
5. Pulling the pipette is carried out as follows:
— heat the middle of the length of tubing over the blue flame (Fig. 2.44);
— keep rotating the tubing until the glass becomes red.
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| Fig. 2.44 Heating the glass tubing before pulling the pipette |
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| Fig. 2.45 Pulling the pipette |
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| Fig. 2.46 Rounding off the ends of the pipette by flaming |
6. Remove the tubing from the flame, still rotating it continuously, and pull the two ends apart slowly, keeping your hands perfectly level (Fig. 2.45). Pull the glass to the length required (10–20 cm).
7. Leave to cool. Cut off the drawn portion at the exact length required. Round off the sharp edges by holding them for a few seconds in the flame (Fig. 2.46). Alternatively, separate and seal the two pipettes by heating the pulled-out por- tion in the flame.
Making a stirring rod
1. Use a glass rod about 5 mm in diameter. Cut the rod into lengths of 15, 20 or 25 cm according to requirements, using a file (see Fig. 2.41).
2. Round off the ends by rotating them over the blue flame of the burner, until about 1 cm of the rod is bright red (Fig. 2.47).
3. Flatten the heated end against the (dry) tiled working surface with a 500-g or 1-kg weight (Fig. 2.48). 4. Heat the other end and press it gently down on the tiled surface (Fig. 2.49). Glass rods can be used to decant liquids or to pour them slowly (see Fig. 3.52).
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| Fig. 2.47 Rounding off the ends of the glass rod by flaming |
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Fig. 2.48 Flattening the heated end of the
glass rod using
a weight
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| Fig. 2.49 Pressing the heated end of the glass rod down on a tiled surface |
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| Fig. 2.50 Heating glass tubing before bending |
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| Fig. 2.51 Bending glass tubing to make a right angle |
Bending glass tubing
1. Heat the spot where the bend is to be made, rotating the tubing over the flame until the glass turns pale red (Fig. 2.50) and sags.
2. Bend the heated tubing slowly to make a right angle (follow the corner of a tile; Fig. 2.51).
Poor bends (Fig. 2.52)
Poor bends may result if:
— the glass was too hot (a)
— the glass was not hot enough (b).
Making a wash bottle
Materials
● Erlenmeyer flask, 1000 ml
● Two pieces of glass tubing
● Cork or rubber stopper.
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| Fig. 2.52 Common problems with bending glass tubing |
Method
Pierce the stopper with a cork borer. Moisten the ends of the tubing with a few drops of water (for cork) or glycerol (for rubber) before inserting them in the holes (Fig. 2.53). Protect your hands with a cloth.
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| Fig. 2.53 Components of a wash bottle |
5. Specimen containers
Different types of containers are used for the collection of specimens such as stools, blood, urine and sputum in the laboratory.
Containers for stool specimens
The following types of container are suitable for the collection of stool specimens (Fig. 2.54):
— waxed cardboard box
— empty tin with a lid
— light plastic box
— glass jar specially designed for stool collection, with a spoon at- tached to the stopper.
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Fig. 2.54 Containers for stool specimens
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Bottles and test-tubes for collecting blood specimens
Without anticoagulant
The best type of test-tube to use for blood specimens is one that can be centrifuged: this avoids excessive handling of the specimen.
● Use clean dr y test-tubes of 5–20 ml capacity, depending on requirements.
With anticoagulant for haematological tests
EDTA dipotassium salt
Put 0.5 ml of EDTA dipotassium salt, 10% solution (reagent no. 22) into each of a series of 5-ml bottles (Fig. 2.55) (or use 0.2 ml in 2-ml bottles). Place the open bottles in an incubator at 37 °C or leave them to dry at room temperature, if no incubator is available.
Use these bottles for:
— blood cell counts
— haemoglobin estimation.
Heparinized tubes
Heparin is an expensive anticoagulant that is not very stable in hot climates. Heparinized tubes are usually obtained commercially or prepared by central labo- ratories and are already marked to show the level to which the blood should be added.
Trisodium citrate
Trisodium citrate, 3.2% solution (reagent no. 60) is used for the determination of the erythrocyte sedimentation rate. Use 1 ml of trisodium citrate solution per 4 ml of blood (or 0.4 ml per 1.6 ml of blood).
Use 1 ml of trisodium citrate solution per 4 ml of blood (or 0.4 ml per 1.6 ml of blood). |
| Fig. 2.55 Dispensing EDTA solution into bottles for collection of blood specimens |
Important: Never carry out a blood cell count on citrated blood.
With anticoagulant for biochemical tests
Sodium fluoride (NaF) is the anticoagulant normally used for biochemical tests. Use 10 mg of sodium fluoride powder per 10 ml of blood, or 2 mg per 2 ml of blood. Use for:
— blood glucose estimation
— blood urea estimation (certain techniques).
War ning: Sodium fluoride is a poison.
Precautions to be taken when using anticoagulants
● Mix as soon as the blood is collected by inverting the bottle several times gently and evenly. Do not shake.
● Use clean bottles. Dry before adding anticoagulant.
War ning: Traces of detergent will dissolve the erythrocytes. Ensure that the bot- tles are rinsed thoroughly before drying.
● Store bottles containing anticoagulants in a dry place. EDTA dipotassium salt solution and sodium fluoride are stable at room temperature but trisodium citrate solution and heparin must be kept in the refrigerator.
● Use the correct proportions. Use bottles and tubes with a graduation mark, or stick on a label so that its upper edge corresponds to the required amount of blood (2 ml, 5 ml, etc.).
Bottles and tubes for collecting other specimens
● Urine — use clean, dry, wide-mouthed Erlenmeyer flasks of 250-ml capacity or clean wide-mouthed bottles.
● Cerebrospinal fluid (CSF) — use test-tubes measuring 150 mm x16 mm. See section 8.2.
Boxes and jars for collecting sputum specimens
Glass screw-top jars or disposable plastic jars with lids can be used for collecting sputum specimens, or small cartons can be made in the laboratory using cardboard and a stapler. These cartons can be used once only for sputum collected in the laboratory.
1. Cut out pieces of thin cardboard 18 cm square and fold them as shown in Fig.2.56:
— first from corner to corner
— then into nine equal squares.
2. Fold the diagonal creases in each corner square inwards (Fig. 2.57).
3. Fold two of the corners back against one side, and the other two against the other side (Fig. 2.58).
4. Staple the two folded corners on each side of the box (Fig. 2.59), which is now ready to receive the specimen.
5. Burn these cartons and plastic jars after use, as described in section 3.6.2.
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| Fig. 2.56 Folding cardboard to make cartons for sputum collection |
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| Fig. 2.57 Folding the corners inwards |
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| Fig. 2.58 Folding two of the corners back against one side of the carton |
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Fig. 2.59 Securing
the folded corners
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6. Storage, stocktaking and ordering supplies
Storage
Glassware
Keep glassware on the shelves of a cupboard away from dust. Erlenmeyer flasks should be plugged with non-absorbent cotton wool or covered with brown paper (or preferably with thin sheets of paraffin wax or clinging plastic, if available) and arranged by type and size. Graduated pipettes should be kept in drawers divided into sections.
Chemicals and reagents
Arrange chemicals and reagents in strict alphabetical order. Acids and inflammable and dangerous chemicals (indicated by appropriately coloured labels) should be stored separately in a special section. Unopened stocks can be kept in crates filled with sawdust.
Poisons (also indicated by appropriately coloured labels) should be stored sepa- rately in a locked cupboard.
Instruments
Some instruments, e.g. spectrophotometers, should be kept in an air-conditioned room if the climate is hot and humid. For storage of microscopes see section 3.1.6.
Stocktaking
Stock cards
A stock card should be prepared for every chemical, stain, piece of glassware, etc. A sample stock card is shown in Table 2.3.
When you order an item, indicate:
— in the column headed “Ordered from”: where you sent the order
— in the column headed “Ordered”: the date and the quantity ordered. When you receive an item, indicate:
— in the column headed “Received”: the date of receipt and the quantity re- ceived
— in the column headed “In stock”: the total in stock in the laboratory after the item has been received.
When an item has been used up (or broken), indicate:
— in the column headed “Issued”: the date of issue and the amount issued
— in the column headed “In stock”: the total left in stock after the item has been issued.
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| Table 2.3 A sample stock card |
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| Table 2.4 Estimating the
quantity of supplies
required |
Classify the stock cards in strictly alphabetical order and keep them in a box or filing drawer. Each item can be given a number, which is then entered on the stock card after the heading “Item no.”.
Inventory
Make an inventory of all laboratory supplies every 6 months. Count the quantity of each item in stock and check that the figure corresponds to the one shown in the “In stock” column of the stock card.
Ordering supplies
A well-organized laboratory should submit an order to the central supply stores every 3 months. To draw up the order, check the stock cards one by one.
It makes it easier to estimate the quantities required if a table summarizing the stock used each month (see Table 2.4) is added to the bottom of each stock card.
In the case of chemicals, stains and reagents, order the quantity used in a 3-month period, taking into account any recent increase or decrease in the amount used. For example:
● Eight bottles of Giemsa stain have been used in a year.
● This gives an average of two bottles used every 3 months.
● Order two bottles every 3 months (or four bottles every 6 months if orders are submitted twice a year).
Expiry dates
Reagents (e.g. blood group antisera, antigens, etc.) have to be used before a certain date. This expiry date should be marked on the container by the supplier. Make a note of the expiry date on the stock card in the column headed “In stock”.
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