114
I BONE-MARROW ASPIRATION
Bone-marrow aspiration R. A. Tozer, MB, ChB, MRCPath Senior Pathologist, Queen Elizabeth Central Hospital, Blantyre, Malawi
TROPICAL DOCTOR,
1978,8, 114-118
Marrow aspiration is a safe, simple, rapid procedure. Examination of the aspirate is of general interest in all anaemias. But in a small group of anaemias and in a few parasitic disorders it may be the only means of making the diagnosis: and in a few other conditions it provides strong support for a presumptive diagnosis. INDICATIONS
Marrow aspiration is indicated whenever the history, clinical findings, and preliminary investigations fail to establish the cause of an anaemia. It should not be attempted until other simpler and perhaps better means of diagnosis have been exhausted. A peripheral blood film, usually thin or thick but sometimes from the buffy layer, gives sufficient indication ofthe cause of an anaemia or suggests the need for marrow aspirate. It should always precede an aspirate. However, it may show little or no abnormality at all in such disorders as carcinomatosis, tuberculosis and malignant lymphoma including Burkitt's lymphoma. Although an aspirate may reveal such a condition, biopsy of a tumour or lymph node is much more likely to give a positive result. In Burkitt's lymphoma, enlargement of peripheral nodes is uncommon: a touch preparation and histology of the tumour itself are diagnostic. There are other disorders in which the need for aspiration is questionable in a district hospital although often recommended. A middle-aged man with clinical features suggestive of leukaemia and a peripheral leucocyte count of 100,000 per mm" or more, almost exclusively mature lymphocytes, almost certainly has chronic lymphatic leukaemia. Marrow aspirate in such a patient simply mirrors the blood findings; and this is so whether he has leukaemia or a pronounced lymphatic leukaemoid reaction as is occasionally seen in tropical splenomegaly syndrome. Pregnant patients in the tropics often present with an alarmingly low haemoglobin and if megaloblasts are seen in the blood film, then this is a megaloblastic anaemia. It may coexist with an iron deficiency anaemia, or be the result of folic acid or vitamin B12 deficiency of pregnancy, or be secondary to malaria or idiopathic tropical splenomegaly. So far as the megaloblastosis goes, marrow aspirate has nothing
Tropical Doctor,July I978 further to offer. Myelomatosis may be diagnosed on radiological findings and urine and blood examinations alone. Each medical officer will decide for himself whether such patients need an aspirate. In a small number of patients marrow aspiration is obligatory if a correct diagnosis and relevant treatment are to be established. They fall into two groups. The larger consists of patients with a variety of clinical presentations and histories but who have some haematological features in common. They have a refractory or recurring anaemia which is often normochromic and normocytic and which may be associated with all or some of the following: leucopenia, thrombocytopenia, clinical or haematological evidence of jaundice or of bleeding and splenomegaly. Such findings offer a wide choice of diagnoses such as aplastic anaemia, leukaemia, haemolytic anaemia, megaloblastic anaemia, idiopathic thrombocytopenic purpura, idiopathic tropical splenomegaly, uraemia, tuberculosis and neoplasm. The correct diagnosis may be ascertained from the marrow and sometimes only from the marrow. In the second group, haemopoiesis is of secondary interest, if any. Aspiration is part of the search for Leishmania donovani in kala azar, Histoplasma capsulatum, or very rarely malaria parasites. The only absolute contraindication to aspiration is haemophilia or other coagulation deficiencies. TECHNIQUE
The following equipment is needed (Fig. I): one 2 ml syringe and needles, two 10 or 20 ml syringes, two marrow needles, one adapter, one piece of filter paper, two spreaders, ten clean' slides, local anaesthetic, 70% ethanol, forceps, swabs, dressing, and collodion. The large syringe is used for aspirating marrow and must be well-fitting. If possible, it is better to use new disposable syringes although they do have one disadvantage; they may break at the junction if the patient moves during aspiration: hence the need for having two. The filter paper simply provides a white background for the two slides on which the marrow is concentrated. Efficient, unbreakable spreaders can be made from old X-ray film which has been cleaned either by leaving it in the fixer for five minutes or by scrubbing in hot water. They should be cut to a little less than the width of a slide and be about an inch long.
Site of the puncture There is a variety of sites. Those chiefly used are the sternum, the iliac crest and, in children less than two years, the medial aspect of the tibia just below the level of the tubercle. The sternum is not ideal; it gives the patient a close, frightening view and is
Tropical Doetor,July I978
. BONE-MARROW ASPIRATION
I lIS
Fig. 2. Klima bone-marrow needle in the left iliac crest.
1. Equipment. The marrow needles are shown with their stilettes partially withdrawn. Salah needle 14t, Klima needle right.
Fig,
immediately anterior to the heart and great vessels. These drawbacks do not exist at other sites. Provided an aseptic and careful technique is used, aspiration is without risk. The most convenient site in many respects is the anterior iliac crest. Method for anterior iliac crest aspiration Have the patient resting comfortably on his back in bed or on an examination couch. It makes the aspiration unnecessarily difficult to attempt it on a child sharing a bed with another or on a floor patient. Young children need a sedative. Explain carefully to the patient what you are about to do. If you are right-handed, stand on the left of the patient and aspirate from his left iliac crest (Fig. 2). Left-banders will probably find it easier to stand on the patient's right and aspirate from his right iliac crest. Identify the anterior superior iliac spine. At a point 1-2 em posterior infiltrate with local anaesthetic
down to and including the periosteum. The crest can usually be gripped easily between finger and thumb. Sometimes a late pregnancy, or (on the left) a very large spleen, or even simple obesity may make this difficult. An assistant can then help by applying gentle pressure on the abdomen away from the iliac crest. Pass the marrow needle perpendicularly into the marrow cavity. It is usually easy to assess when the needle has entered because there is a yielding sensation. Remove the stilette and apply the 10 ml syringe and adapter. Warn the patient that he will feel momentary pain but that he must remain still. Aspirate firmly but briefly. One aspiration usually provides adequate marrow (0.25-0.5 ml) immediately. Leave the needle in situ and disconnect the syringe; place a swab on the needle. Aspiration can then be repeated if necessary. If there is any difficulty,
Fig. ]. Concentration technique. Fragments adhere to the upper slide. Same aspirate as in Fig. 4.
1161 BONE-MARROW ASPIRATION
Tropical Doctor, July I978 Sometimes an apparent dry tap occurs even though the needle is in the cavity. There is often a little aspirate in the needle. Withdraw both syringe and needle and expel the contents of the needle. It may make only one film but that film may be diagnostic. There is little to be gained from squash preparations. Technique for histology and culture of marrow vary from place to place. For these investigations seek the advice of the referral laboratory. Provided adequate marrow is obtained on the first aspiration, four or five minutes usually elapse, and sometimes longer, before the specimen clots. If there is some delay in obtaining the aspirate after the needle has entered the cavity, clotting is much more rapid. It is possible to collect marrow into EDTA as for peripheral blood, to prevent clotting. If this is done, films should be made as soon as possible, preferably within an hour. Even then, there may be artefacts in the cells themselves or in the background derived from the EDTA. The main purpose of marrow aspiration is to make good films. This is best done by making them at the time of aspiration. With a little practice, they can readily be made before clotting occurs.
Fig. 4. Labelled slidewith a cover slip showing a marrow with highfragment density. replace the stilette, rotate the needle, push it forward a little and try again. Gently expel part of the contents of the syringe on to one of the two slides on the filter paper, the rest being used for culture or histology, if desired. Let the marrow spread over the slide; then tilt the slide on to the other. The fluid part will run off carrying some of the marrow particles but leaving other; adhering to the original slide (Fig. 3). At this point, it will be obvious whether the aspirate is adequate. If it is, the needle can quickly be removed and either an assistant or the patient asked to press on the overlying swab prior to applying collodion. Pick off several particles with the spreader and make a film which should extend about halfway along the slide (Fig. 4). Make several films in this way. If the marrow particles are scanty, repeat the concentration by tilting the specimen back on to the original slide. Dry the slides by waving them in the air and pencil the patient's name in the base of the body of the blood film.
Other sites for puncture If the iliac crest is very narrow, as happens sometimes in small children, make the puncture 2 em posterior and 2 em inferior to the anterior superior iliac spine. If aspiration is attempted from the sternum, either in the manubrium or in the second interspace, or from the tibia, it is easier for a right-handed person if he stands on the right of the patient. Fixing and staining Films are fixed in methanol for 20 minutes as soon as possible after drying. If left unfixed, they may be eaten by insects.
Fig. 5. Microscope pictureof a normoblastic marrow.
Tropical Doctor, July I978
BONE-MARROW ASPIRATION
I 117
Fig. 6. Marrow in acute monocytic leukaemia.
Fig. 7. Marrow in Burkitt's lymphoma.
Marrow films are stained in the same way as peripheral blood films but take a little longer. For example, Leishman's stain takes about half as long again as for blood films; the precise time varies and has to be established by trial and error. Leishman's stain is one of the Romanowsky stains, all of which are suitable both for marrow cells and for parasites of kala azar, histoplasmosis, and malaria. It is better to leave additional staining, such as for iron, to the pathologist who may also wish to use a different Romanowsky stain. When examining a stained film at any magnification, place a drop of immersion oil surmounted by a cover slip at the junction of the body and tail.
those due to haemolysis and hypersplenism, usually have a hypercellular marrow. In chronic illnesses such as uraemia and tuberculosis, the marrow is mildly hypocellular and in aplasia from any cause, markedly so. In leukaemias, the marrow is usually hypercellular. At magnifications of x 10 and x 40, the most striking single aspect of normal marrow is the wide variety of cells due mostly to the mature and developing cells of the myeloid series (Fig. 6). This contrasts markedly with the more or less uniform appearance usually seen in acute leukaemia (Figs 7 and 8), chronic lymphatic leukaemia, some cases of myelomatosis, and with the absence of most cell lines in hypoplasia. In haemolytic anaemias, erythroid precursors are greatly increased and may comprise more than half the nucleated cells present; usually they are less than a quarter. In chronic illnesses, plasma cells may show a modest increase, and in aplasia a more marked increase of up to about 15% of nucleated cells. The mode of development of each cell line and the correct identification of abnormal cells and parasites
INTERPRETATION
Marrow aspirate can be satisfactorily interpreted only when the history, clinical findings, investigations, and previous treatment are known. The medical officer who is conversant with such facts at first hand is in an ideal position to make his own interpretation before sending the slides on to the pathologist. Interpretation is based on : cellularity, both absolute and relative; mode of development of each cell line; presence of extramedullary cells or parasites. A well-made marrow slide has macroscopically recognizable marrow fragments at the tail. The degree of absolute cellularity is assessed chiefly from these. Very roughly, a normocellular fragment contains from about 25";.-5°°0 fat cells which are the unstained areas in the fragment. The percentage depends partly on age, becoming greatest in old age. Cellularity can sometimes be assessed from cell trails but they are less reliable: an intensely cellular fragment may leave almost no cell trail. Cellularity can be quickly assessed using the low power objectives (x 3 and x 10) as normal, increased, or reduced. Anaemias due to deficiencies of iron, folic acid, and vitamin B u, and
!;~~~:'i=~ 16~ , t· .. ~.
,.
~/ .~:it~ Fig.
x.
Megaloblastic marrow.
118
I BONE-MARROW ASPIRATION
Tropical Doctor, July I978
• Fig. 9. Leishmania donovani in the cytoplasm of a phagocyte, in an aspirate from bone-marrow. is more difficult. The best way of doing this is to have microphotographs and good drawings with which to compare the slide. Haematological atlases are helpful but expensive. Good photographs and drawings are to be found in the books quoted under References: It is important to relate clinical data to interpretation. For example, pregnancy usually causes an
increase in cellularity and may lead to megaloblastosis; blood transfusion or antimitotic therapy may suppress haemopoiesis; treatment with vitamin B12 or folic acid may convert a megaloblastic marrow into a normoblastic one within hours. A dry tap or an aspirate containing only peripheral blood poses problems both in technique and interpretation. It is reasonable to attempt a second aspiration at a second site if the first fails. If the second fails, it is better to send the patient to the pathologist. It is unreasonable to make a definite interpretation of a dry tap. It may occur when the marrow is packed full of cells as in leukaemia while paradoxically an aplastic marrow may yield a large number of empty marrow fragments. REFERENCES
Cheesbrough, M., and McArthur, J. (1976). A Laboratory Manual for Rural Tropical Hospitals. London and Edinburgh: Churchill Livingstone. Hayhoe, F. G. H., and Flemans, R. J. (1969). A Colour Atlas of Haematological Cytology. London: Wolfe. Jeffrey, H. C., and Leach, R. M. (1975). Atlas of Medical Helminthology and Protozoology. London and Edinburgh: Livingstone. King, M. (1974). A Medical Laboratory for Developing Countries. London: Oxford University Press.
Any Questions? What is the best method of sterilizing rubber gloves in a small hospital which has no mains electricity? We are thinking of buying a kerosene-heated autoclave. Will this be suitable and will it produce dry, sterile gloves?
Autoclaving is the best method of sterilizing rubber gloves in your circumstances. They should be placed high in the autoclave chamber and be dealt with as a separate load by themselves. A suitable exposure to steam is 15 minutes at 121°C. The pre- and poststerilizing phases of the autoclave cycle should be kept as short as possible to protect the rubber. Autoclaves designed to run off a kerosene or gas burner are usually of the "downward displacement'.' type in which saturated steam is produced in a container beneath and admitted to the top of the sterilizing chamber, so displacing air downwards. Replacement of air by steam in this way is rather slow. After the sterilizing phase, heat is shut off and the steam vented away. The chamber is then left closed for long enough to allow the contents to dry. In the absence of an induced vacuum, this stage also is prolonged, and
it is at this time that the rubber goods are damaged. The instructions given above are meant to minimize this damage. Other desirable features in an autoclave are a horizontal, circular drum; a single, circular door; and a small chamber capacity. The smaller the capacity, the shorter the whole process and the less the damage to rubber and other soft goods. It is more efficient and in the long run more economical to use a small autoclave several times a day than to use too large a machine once. The alternatives to autoclaving are all distinctly unsatisfactory but there are two methods which can be used in emergency: (a) gloves can be boiled for 20 minutes at atmospheric pressure, cooledby dipping in cold, boiled water, and put on wet; (b) the hands are washed in the usual way, dried and inserted in a fresh dry pair of gloves, and the ritual wash of the gloved hands repeated for five minutes using betadine or similar antiseptic soap or a terminal rinse in chlorhexidine in 70"" spirit. JOHN COOK, CHM, FRCS(EDIN), FRSE
Royal College of Surgeons, Edinburgh, Scotland
I BONE-MARROW ASPIRATION
Bone-marrow aspiration R. A. Tozer, MB, ChB, MRCPath Senior Pathologist, Queen Elizabeth Central Hospital, Blantyre, Malawi
TROPICAL DOCTOR,
1978,8, 114-118
Marrow aspiration is a safe, simple, rapid procedure. Examination of the aspirate is of general interest in all anaemias. But in a small group of anaemias and in a few parasitic disorders it may be the only means of making the diagnosis: and in a few other conditions it provides strong support for a presumptive diagnosis. INDICATIONS
Marrow aspiration is indicated whenever the history, clinical findings, and preliminary investigations fail to establish the cause of an anaemia. It should not be attempted until other simpler and perhaps better means of diagnosis have been exhausted. A peripheral blood film, usually thin or thick but sometimes from the buffy layer, gives sufficient indication ofthe cause of an anaemia or suggests the need for marrow aspirate. It should always precede an aspirate. However, it may show little or no abnormality at all in such disorders as carcinomatosis, tuberculosis and malignant lymphoma including Burkitt's lymphoma. Although an aspirate may reveal such a condition, biopsy of a tumour or lymph node is much more likely to give a positive result. In Burkitt's lymphoma, enlargement of peripheral nodes is uncommon: a touch preparation and histology of the tumour itself are diagnostic. There are other disorders in which the need for aspiration is questionable in a district hospital although often recommended. A middle-aged man with clinical features suggestive of leukaemia and a peripheral leucocyte count of 100,000 per mm" or more, almost exclusively mature lymphocytes, almost certainly has chronic lymphatic leukaemia. Marrow aspirate in such a patient simply mirrors the blood findings; and this is so whether he has leukaemia or a pronounced lymphatic leukaemoid reaction as is occasionally seen in tropical splenomegaly syndrome. Pregnant patients in the tropics often present with an alarmingly low haemoglobin and if megaloblasts are seen in the blood film, then this is a megaloblastic anaemia. It may coexist with an iron deficiency anaemia, or be the result of folic acid or vitamin B12 deficiency of pregnancy, or be secondary to malaria or idiopathic tropical splenomegaly. So far as the megaloblastosis goes, marrow aspirate has nothing
Tropical Doctor,July I978 further to offer. Myelomatosis may be diagnosed on radiological findings and urine and blood examinations alone. Each medical officer will decide for himself whether such patients need an aspirate. In a small number of patients marrow aspiration is obligatory if a correct diagnosis and relevant treatment are to be established. They fall into two groups. The larger consists of patients with a variety of clinical presentations and histories but who have some haematological features in common. They have a refractory or recurring anaemia which is often normochromic and normocytic and which may be associated with all or some of the following: leucopenia, thrombocytopenia, clinical or haematological evidence of jaundice or of bleeding and splenomegaly. Such findings offer a wide choice of diagnoses such as aplastic anaemia, leukaemia, haemolytic anaemia, megaloblastic anaemia, idiopathic thrombocytopenic purpura, idiopathic tropical splenomegaly, uraemia, tuberculosis and neoplasm. The correct diagnosis may be ascertained from the marrow and sometimes only from the marrow. In the second group, haemopoiesis is of secondary interest, if any. Aspiration is part of the search for Leishmania donovani in kala azar, Histoplasma capsulatum, or very rarely malaria parasites. The only absolute contraindication to aspiration is haemophilia or other coagulation deficiencies. TECHNIQUE
The following equipment is needed (Fig. I): one 2 ml syringe and needles, two 10 or 20 ml syringes, two marrow needles, one adapter, one piece of filter paper, two spreaders, ten clean' slides, local anaesthetic, 70% ethanol, forceps, swabs, dressing, and collodion. The large syringe is used for aspirating marrow and must be well-fitting. If possible, it is better to use new disposable syringes although they do have one disadvantage; they may break at the junction if the patient moves during aspiration: hence the need for having two. The filter paper simply provides a white background for the two slides on which the marrow is concentrated. Efficient, unbreakable spreaders can be made from old X-ray film which has been cleaned either by leaving it in the fixer for five minutes or by scrubbing in hot water. They should be cut to a little less than the width of a slide and be about an inch long.
Site of the puncture There is a variety of sites. Those chiefly used are the sternum, the iliac crest and, in children less than two years, the medial aspect of the tibia just below the level of the tubercle. The sternum is not ideal; it gives the patient a close, frightening view and is
Tropical Doetor,July I978
. BONE-MARROW ASPIRATION
I lIS
Fig. 2. Klima bone-marrow needle in the left iliac crest.
1. Equipment. The marrow needles are shown with their stilettes partially withdrawn. Salah needle 14t, Klima needle right.
Fig,
immediately anterior to the heart and great vessels. These drawbacks do not exist at other sites. Provided an aseptic and careful technique is used, aspiration is without risk. The most convenient site in many respects is the anterior iliac crest. Method for anterior iliac crest aspiration Have the patient resting comfortably on his back in bed or on an examination couch. It makes the aspiration unnecessarily difficult to attempt it on a child sharing a bed with another or on a floor patient. Young children need a sedative. Explain carefully to the patient what you are about to do. If you are right-handed, stand on the left of the patient and aspirate from his left iliac crest (Fig. 2). Left-banders will probably find it easier to stand on the patient's right and aspirate from his right iliac crest. Identify the anterior superior iliac spine. At a point 1-2 em posterior infiltrate with local anaesthetic
down to and including the periosteum. The crest can usually be gripped easily between finger and thumb. Sometimes a late pregnancy, or (on the left) a very large spleen, or even simple obesity may make this difficult. An assistant can then help by applying gentle pressure on the abdomen away from the iliac crest. Pass the marrow needle perpendicularly into the marrow cavity. It is usually easy to assess when the needle has entered because there is a yielding sensation. Remove the stilette and apply the 10 ml syringe and adapter. Warn the patient that he will feel momentary pain but that he must remain still. Aspirate firmly but briefly. One aspiration usually provides adequate marrow (0.25-0.5 ml) immediately. Leave the needle in situ and disconnect the syringe; place a swab on the needle. Aspiration can then be repeated if necessary. If there is any difficulty,
Fig. ]. Concentration technique. Fragments adhere to the upper slide. Same aspirate as in Fig. 4.
1161 BONE-MARROW ASPIRATION
Tropical Doctor, July I978 Sometimes an apparent dry tap occurs even though the needle is in the cavity. There is often a little aspirate in the needle. Withdraw both syringe and needle and expel the contents of the needle. It may make only one film but that film may be diagnostic. There is little to be gained from squash preparations. Technique for histology and culture of marrow vary from place to place. For these investigations seek the advice of the referral laboratory. Provided adequate marrow is obtained on the first aspiration, four or five minutes usually elapse, and sometimes longer, before the specimen clots. If there is some delay in obtaining the aspirate after the needle has entered the cavity, clotting is much more rapid. It is possible to collect marrow into EDTA as for peripheral blood, to prevent clotting. If this is done, films should be made as soon as possible, preferably within an hour. Even then, there may be artefacts in the cells themselves or in the background derived from the EDTA. The main purpose of marrow aspiration is to make good films. This is best done by making them at the time of aspiration. With a little practice, they can readily be made before clotting occurs.
Fig. 4. Labelled slidewith a cover slip showing a marrow with highfragment density. replace the stilette, rotate the needle, push it forward a little and try again. Gently expel part of the contents of the syringe on to one of the two slides on the filter paper, the rest being used for culture or histology, if desired. Let the marrow spread over the slide; then tilt the slide on to the other. The fluid part will run off carrying some of the marrow particles but leaving other; adhering to the original slide (Fig. 3). At this point, it will be obvious whether the aspirate is adequate. If it is, the needle can quickly be removed and either an assistant or the patient asked to press on the overlying swab prior to applying collodion. Pick off several particles with the spreader and make a film which should extend about halfway along the slide (Fig. 4). Make several films in this way. If the marrow particles are scanty, repeat the concentration by tilting the specimen back on to the original slide. Dry the slides by waving them in the air and pencil the patient's name in the base of the body of the blood film.
Other sites for puncture If the iliac crest is very narrow, as happens sometimes in small children, make the puncture 2 em posterior and 2 em inferior to the anterior superior iliac spine. If aspiration is attempted from the sternum, either in the manubrium or in the second interspace, or from the tibia, it is easier for a right-handed person if he stands on the right of the patient. Fixing and staining Films are fixed in methanol for 20 minutes as soon as possible after drying. If left unfixed, they may be eaten by insects.
Fig. 5. Microscope pictureof a normoblastic marrow.
Tropical Doctor, July I978
BONE-MARROW ASPIRATION
I 117
Fig. 6. Marrow in acute monocytic leukaemia.
Fig. 7. Marrow in Burkitt's lymphoma.
Marrow films are stained in the same way as peripheral blood films but take a little longer. For example, Leishman's stain takes about half as long again as for blood films; the precise time varies and has to be established by trial and error. Leishman's stain is one of the Romanowsky stains, all of which are suitable both for marrow cells and for parasites of kala azar, histoplasmosis, and malaria. It is better to leave additional staining, such as for iron, to the pathologist who may also wish to use a different Romanowsky stain. When examining a stained film at any magnification, place a drop of immersion oil surmounted by a cover slip at the junction of the body and tail.
those due to haemolysis and hypersplenism, usually have a hypercellular marrow. In chronic illnesses such as uraemia and tuberculosis, the marrow is mildly hypocellular and in aplasia from any cause, markedly so. In leukaemias, the marrow is usually hypercellular. At magnifications of x 10 and x 40, the most striking single aspect of normal marrow is the wide variety of cells due mostly to the mature and developing cells of the myeloid series (Fig. 6). This contrasts markedly with the more or less uniform appearance usually seen in acute leukaemia (Figs 7 and 8), chronic lymphatic leukaemia, some cases of myelomatosis, and with the absence of most cell lines in hypoplasia. In haemolytic anaemias, erythroid precursors are greatly increased and may comprise more than half the nucleated cells present; usually they are less than a quarter. In chronic illnesses, plasma cells may show a modest increase, and in aplasia a more marked increase of up to about 15% of nucleated cells. The mode of development of each cell line and the correct identification of abnormal cells and parasites
INTERPRETATION
Marrow aspirate can be satisfactorily interpreted only when the history, clinical findings, investigations, and previous treatment are known. The medical officer who is conversant with such facts at first hand is in an ideal position to make his own interpretation before sending the slides on to the pathologist. Interpretation is based on : cellularity, both absolute and relative; mode of development of each cell line; presence of extramedullary cells or parasites. A well-made marrow slide has macroscopically recognizable marrow fragments at the tail. The degree of absolute cellularity is assessed chiefly from these. Very roughly, a normocellular fragment contains from about 25";.-5°°0 fat cells which are the unstained areas in the fragment. The percentage depends partly on age, becoming greatest in old age. Cellularity can sometimes be assessed from cell trails but they are less reliable: an intensely cellular fragment may leave almost no cell trail. Cellularity can be quickly assessed using the low power objectives (x 3 and x 10) as normal, increased, or reduced. Anaemias due to deficiencies of iron, folic acid, and vitamin B u, and
!;~~~:'i=~ 16~ , t· .. ~.
,.
~/ .~:it~ Fig.
x.
Megaloblastic marrow.
118
I BONE-MARROW ASPIRATION
Tropical Doctor, July I978
• Fig. 9. Leishmania donovani in the cytoplasm of a phagocyte, in an aspirate from bone-marrow. is more difficult. The best way of doing this is to have microphotographs and good drawings with which to compare the slide. Haematological atlases are helpful but expensive. Good photographs and drawings are to be found in the books quoted under References: It is important to relate clinical data to interpretation. For example, pregnancy usually causes an
increase in cellularity and may lead to megaloblastosis; blood transfusion or antimitotic therapy may suppress haemopoiesis; treatment with vitamin B12 or folic acid may convert a megaloblastic marrow into a normoblastic one within hours. A dry tap or an aspirate containing only peripheral blood poses problems both in technique and interpretation. It is reasonable to attempt a second aspiration at a second site if the first fails. If the second fails, it is better to send the patient to the pathologist. It is unreasonable to make a definite interpretation of a dry tap. It may occur when the marrow is packed full of cells as in leukaemia while paradoxically an aplastic marrow may yield a large number of empty marrow fragments. REFERENCES
Cheesbrough, M., and McArthur, J. (1976). A Laboratory Manual for Rural Tropical Hospitals. London and Edinburgh: Churchill Livingstone. Hayhoe, F. G. H., and Flemans, R. J. (1969). A Colour Atlas of Haematological Cytology. London: Wolfe. Jeffrey, H. C., and Leach, R. M. (1975). Atlas of Medical Helminthology and Protozoology. London and Edinburgh: Livingstone. King, M. (1974). A Medical Laboratory for Developing Countries. London: Oxford University Press.
Any Questions? What is the best method of sterilizing rubber gloves in a small hospital which has no mains electricity? We are thinking of buying a kerosene-heated autoclave. Will this be suitable and will it produce dry, sterile gloves?
Autoclaving is the best method of sterilizing rubber gloves in your circumstances. They should be placed high in the autoclave chamber and be dealt with as a separate load by themselves. A suitable exposure to steam is 15 minutes at 121°C. The pre- and poststerilizing phases of the autoclave cycle should be kept as short as possible to protect the rubber. Autoclaves designed to run off a kerosene or gas burner are usually of the "downward displacement'.' type in which saturated steam is produced in a container beneath and admitted to the top of the sterilizing chamber, so displacing air downwards. Replacement of air by steam in this way is rather slow. After the sterilizing phase, heat is shut off and the steam vented away. The chamber is then left closed for long enough to allow the contents to dry. In the absence of an induced vacuum, this stage also is prolonged, and
it is at this time that the rubber goods are damaged. The instructions given above are meant to minimize this damage. Other desirable features in an autoclave are a horizontal, circular drum; a single, circular door; and a small chamber capacity. The smaller the capacity, the shorter the whole process and the less the damage to rubber and other soft goods. It is more efficient and in the long run more economical to use a small autoclave several times a day than to use too large a machine once. The alternatives to autoclaving are all distinctly unsatisfactory but there are two methods which can be used in emergency: (a) gloves can be boiled for 20 minutes at atmospheric pressure, cooledby dipping in cold, boiled water, and put on wet; (b) the hands are washed in the usual way, dried and inserted in a fresh dry pair of gloves, and the ritual wash of the gloved hands repeated for five minutes using betadine or similar antiseptic soap or a terminal rinse in chlorhexidine in 70"" spirit. JOHN COOK, CHM, FRCS(EDIN), FRSE
Royal College of Surgeons, Edinburgh, Scotland
