Haematology in Under-Resourced Laboratories

Introduction: types of laboratories

In most countries, there are likely to be some laboratories with limited resources, but in under-resourced countries, the majority of laboratories face chronic shortages of trained staff, low morale, inadequate and poorly maintained equipment and erratic supplies of reagents and essential supplies. These factors have a major impact on the range and quality of services offered. Many laboratories lack the highly sophisticated equipment found in better resourced settings and some still operate using predominantly manual techniques. The most peripheral laboratories tend to be multifunctional, with staff performing a range of haematology, parasitology, clinical chemistry and microbiology tests. A blood transfusion service is usually available at larger facilities and, although nationally organised blood services are expanding, much blood for donation is still sourced and used at individual hospital level. In practice this means that laboratory staff may be responsible for donor selection, blood collection and issuing of blood. If there is no separate system of public health laboratories, clinical laboratories may also be required to provide reliable health surveillance data for epidemiological and public health monitoring and to investigate disease outbreaks and refer samples for confirmation.

In under-resourced countries, these difficulties are compounded by the high burden of infectious diseases such as malaria, human immunodeficiency virus infection/acquired immune deficiency syndrome (HIV/AIDS), tuberculosis and neglected tropical diseases such as schistosomiasis and helminthiasis. There are also additional pressures from external agencies such as donors, funders and research projects which may not align closely with local public health priorities. Parasitological diagnosis is now recommended for all suspected cases of malaria to prevent overdiagnosis and reduce inappropriate use of antimalarial drugs. World Health Organisation (WHO) guidelines state that malaria treatment based on clinical grounds should only be given if diagnostic testing is not immediately accessible within 2 h of patients presenting for treatment. In higher level or specialised treatment centres, the diagnosis of leishmaniasis may require aspiration of bone marrow or splenic pulp. The diagnosis of tuberculosis may require aspiration and culture of bone marrow and trephine biopsy examination, especially in patients who are HIV positive, in whom sputum tests for acid-fast organisms are frequently negative. The decision to initiate antiretroviral therapy, to switch to second-line drugs and the monitoring of therapy require regular haemoglobin concentration (Hb) measurements, CD4-positive lymphocyte counts (or percentages for paediatric care) and, ideally, plasma viral load determinations (HIV ribonucleic acid (RNA) monitoring), although provision of some of these tests is challenging for low-income countries. ^,

The purpose of this chapter is to provide guidance for an effective haematology service at the different levels of the healthcare system in resource-limited countries. In planning such services, it is necessary to determine what tests are needed at each level, to ensure that tests are reliable and accurate and to establish effective referral networks for patients and samples. In some cases this may involve regional and international partnerships if resources for quality diagnoses are not available in-country.

Organisation of clinical laboratory services

In under-resourced countries clinical laboratory services may be considered at four levels according to size, staffing and services offered. These levels are: primary facilities, including subdistrict hospitals and health centres (Level 1); intermediate facilities, including district and county hospitals (Level 2); regional and provincial hospitals (Level 3); and national referral and teaching hospitals (Level 4) ( Fig. 26-1 ).

Level 1: primary and subdistrict laboratories

Level 1 laboratories provide first-line diagnostic services to support patient management decisions, initial public health investigations and specimen referral. Laboratory staff may comprise one or two qualified laboratory technicians supported by assistants who often have little or no formal training but have learnt various techniques at the bench. In very peripheral settings, there may be no formal laboratory, and some point-of-care tests are carried out by nurses or assistants with limited training. There is increasing availability of point-of-care diagnostics for an expanding repertoire of conditions, which while enabling more patients to access diagnostic tests, requires adherence to standards to ensure test quality, satisfactory operator performance and correct use of results for patient treatment. This ‘task shifting’ may be an increased burden for already overworked staff and requires intensive supervision and quality monitoring. Maintenance of equipment in rural areas is often difficult, which can significantly compromise the quality of results or interrupt services altogether. Haematology laboratory tests at this level generally include a method for measuring Hb; microscopy for malaria and other blood parasites, blood cell morphology; and HIV and sickle cell screening.

Level 2: intermediate (district) level laboratories

Intermediate level laboratories are usually multipurpose, and perform microbiological and biochemical as well as haematological tests. Laboratory staff may comprise a limited number of qualified laboratory technicians or biomedical scientists. Equipment available for haematology may include a microscope, centrifuge and basic colorimeter for measurement of Hb. In some intermediate laboratories more sophisticated equipment such as automated haematology and clinical chemistry analysers are available, but long-term sustainability requires funding for regular servicing and maintenance at the time of procurement and installation and purchase of appropriate reagents. In the absence of access to a national blood service, intermediate hospital laboratories are responsible for blood transfusion services with the laboratory expected to perform blood grouping and crossmatching as well as screening for HIV, hepatitis B virus (HBV), hepatitis C virus (HCV) and syphilis.

Level 3: regional and provincial hospitals

At this level, laboratory staff have usually received multidisciplinary training and specialist laboratory staff are available. Level 3 laboratories are usually multipurpose, performing microbiological, biochemical and haematological tests, as well as some more specialised tests. Automated haematology and chemistry equipment, and tests such as CD4-positive lymphocyte counting and coagulation tests are available.

Level 4: national referral and teaching hospitals

At this level, laboratory staff have usually received multidisciplinary training and some of the senior staff have received postgraduate training in a specialist laboratory discipline. Each laboratory usually has a specialist technical head who works closely with the clinician responsible for laboratory services. Equipment generally available includes centrifuges, colorimeters, microscopes, haemoglobin electrophoresis equipment, automated haematology and clinical chemistry and blood grouping and crossmatching analysers, and possibly high performance liquid chromatography and blood bank centrifuges for the separation of blood components.

Availability of haematology tests at each level

In under-resourced countries, haematology tests available at the different levels of healthcare vary widely and depend on local clinical and public health needs as well as availability of equipment and qualified technical laboratory personnel. The following is a general description of the haematology-related tests that are likely to be required at each level.

Level 1

Hb measurement by a manual method (see p. 22)
Malaria and other blood parasite testing on thick and thin peripheral blood films (see p. 101) or rapid malaria diagnostic test (see p. 102)
Peripheral blood cell morphology, especially to identify the cause of anaemia
Sickle cell screening
Testing for HIV for blood transfusion screening

Level 2

Hb measurement (see p. 19)
Peripheral blood cell morphology
Total white blood cell counts (see p. 36)
Differential white cell count (see p. 25)
Platelet estimates (usually from blood film)
CD4-positive lymphocyte count (see p. 557)
Malaria and other blood parasite testing by thick and thin peripheral blood films (see p. 101) or rapid diagnostic test for Plasmodium falciparum and other species (see p. 102)
Screening test for sickle haemoglobin in areas where this is relevant (see p. 297)
Blood grouping and compatibility testing ( Chapter 21 )
Testing for HIV, HBV, HCV and syphilis infection for blood transfusion screening
Some larger laboratories may be able to provide automated measurements of Hb, mean cell volume (MCV), mean cell haemoglobin (MCH), mean cell haemoglobin concentration (MCHC), white blood cell total count (WBC), differential count and platelet count (see p. 30).

Levels 3 and 4

In addition to tests carried out at level 2, the haematology services offered by level 3 and 4 laboratories may include the following:

Automated Hb, MCV, MCH, MCHC, WBC and differential counts, platelet counts (see p. 30)
Haemoglobin electrophoresis or high performance liquid chromatography ( Chapter 14 )
Haemoglobin A ₂ and haemoglobin F measurements (see pp. 302 and 306)
Glucose-6-phosphate dehydrogenase screen (by fluorescent spot or methaemoglobin reduction method) or molecular methods (see p. 238)
Flow cytometric immunophenotyping (see Chapter 16 )
Polymerase chain reaction (PCR) or other method for diagnosis of mutations associated with haematological malignancies (see Chapter 23 )
HIV plasma viral load estimations
Staining of bone marrow films for morphological assessment (see p. 52) and estimation of iron status (see p. 120)
Bone marrow trephine biopsy examination (see p. 120)
Identification of blood group antibodies (see Chapter 21 )
Basic clotting screen (prothrombin time (PT), thrombin time (TT) and activated partial thromboplastin time (APTT)) and possibly thrombophilia tests (see p. 410)
Oral anticoagulant control (see p. 426)
Separation of whole blood into packed cells, plasma and, occasionally, platelets and cryoprecipitate.

Microscopes

The microscope is the most important piece of laboratory equipment in under-resourced countries and is essential for the diagnosis of anaemia, malaria and other blood parasitic infections and for performing differential white blood cell counts and sickle cell screening tests. Reliable assessment of morphological features requires a microscope that is clean and correctly set up with aligned lenses and an electric light source (either inbuilt or reflected light) to ensure clear images, especially at high magnification. Failure to maintain microscopes to a high standard through routine user maintenance or, ideally, with regular professional servicing, can lead to inaccurate diagnoses and inefficient use of technician time. ^, Routine maintenance of the microscope is described on p. 46.

Care of the microscope

In hot, humid climates, if no precautions are taken, fungus may grow on the surface of the lenses, in the grooves of the screws and under the paint. This can be prevented by placing the microscope every evening in an airtight dust cover together with silica gel. Dry the silica as necessary and reuse it. An alternative method is to place the microscope in a warm cupboard with a tight-fitting door, heated by a 40-watt light bulb. Check that the temperature inside the cupboard is at least 5 °C warmer than that of the laboratory, but take care that it does not overheat.

In hot, dry climates, the main problem is dust. Fine particles work their way into the threads of the screws and under the lenses. This can be avoided as follows:

1.
Always keep the microscope under a dustproof plastic cover when not in use.
2.
At the end of the day’s work, clean the microscope thoroughly by blowing air onto the lenses and moving parts.
3.
Finish cleaning the lenses with a lens brush or fine paintbrush. If dust particles remain on the surface of the objectives, remove with a clean lens tissue.

Essential haematology tests

Despite the relatively high cost of running a laboratory service and the low per capita healthcare budget in under-resourced countries, there is little guidance available on how to make rational decisions on the choice of ‘essential’ laboratory tests. ^, Decisions about which tests to provide must be made in consultation with laboratory professionals and clinical staff. The selection of ‘essential’ tests at each level should be based on the clinical and public health needs of the local community and the availability of qualified clinical and laboratory staff, as well as the availability of funds. Essential test packages are usually defined as part of national policy and standards, taking into consideration medium- and long-term trends and the requirements of disease control programmes.

To ensure cost-effectiveness of the laboratory service, tests with no proven value should be eliminated and new tests for which there is independent evidence of clinical usefulness should be introduced, as described in Chapter 24 . Tests that provide objective qualitative or quantitative information are preferred. Although it is not possible to draw up a list of essential tests applicable to all countries, or even to different regions within a country, the following aspects should be considered.

Cost per test

Often the cost of a test is calculated from the price of reagents divided by the number of tests performed. However, this oversimplifies the situation and is not accurate enough to form the basis for national policy decisions and budget allocation. The factors that need to be taken into account when calculating the total annual costs for a laboratory are given in Chapter 24 .

Diagnostic reliability

It is important to know the sensitivity and specificity of a test and its predictive values (as calculated on p. 568) when selecting a laboratory test for clinical use. This information may be provided by manufacturers but may not be locally applicable, and local test evaluation data are usually not available in under-resourced countries. In some countries, the ‘gold standard’ diagnostic services needed to determine ‘true positive’ and ‘true negative’ data in the local context are also lacking.

The quality of all tests carried out by a laboratory should be regularly monitored. Systems for achieving this are well established (see Chapter 24 ) but are not easily implemented in under-resourced settings. The quality of a test influences its usefulness as well as its utilisation by clinicians and community members. For example, if the result of a test in routine practice is correct only 80% of the time, then one in five tests will be wasted, reducing the effectiveness of the test by 20%. Furthermore, an inaccurate test may result in a patient receiving inappropriate treatment. Clinicians and the general public are increasingly aware of the need for reliable services. Clinicians may not order tests or use the results in patient management decisions if they do not trust the quality of the laboratory results, and poor quality healthcare may deter patients from using health facilities.

Clinical usefulness

An assessment of the clinical usefulness of a test should be carried out by an independent clinician who is familiar with local diseases and the diagnostic support services available. This assessor needs to compare actual clinical practice with locally agreed ‘best practice’ or, if available, local guidelines. From observation of a range of clinical interactions, the percentage of times that ideal practice is followed can be calculated. For example, transfusion guidelines may recommend that, apart from specified clinical conditions, transfusions should be given only to children with an Hb of < 50 g/l. The assessor can record how many children with Hb below this level failed to receive a transfusion and how many transfusions were given without waiting for the Hb result or at an inappropriate Hb level. For each test, the assessor needs to judge whether the test has been appropriately requested and has been used to influence patient management or public health decisions. The percentage of tests that are not used to guide clinical decisions will provide a figure for ‘clinical wastage’ of the test that can be entered into a simple formula ( Chapter 24 ).

Maintaining quality and reliability of tests

Paradoxically, it is in under-resourced laboratories, where equipment and supplies are limited and training and supervision may be minimal, that the level of skills and motivation required to maintain a good-quality service need to be highest. Even the most basic of laboratories should ensure that procedures are in place to monitor quality (see Chapter 25 ). In addition to monitoring the technical quality of each test, quality management and improvement processes should be in place throughout the laboratory. The Centers for Disease Control and Prevention/World Health Organisation (CDC/WHO) WHO Guide for the Stepwise Laboratory Improvement Process Towards Accreditation (SLIPTA) in the African Region , being rolled out in developing countries provides a structured quality improvement process comprising workshop-based teaching, laboratory quality improvement projects, on-site mentoring and regular assessments over a period of time (up to 2 years). Standard operating procedures (SOPs) (see p. 523) should be available for every procedure performed in the laboratory; these can be adapted from existing SOP ‘models’. In addition to providing standardised techniques, SOPs are excellent teaching resources, and adherence to these procedures will minimise errors. SOPs need to be regularly reviewed and updated to keep pace with technical developments and changes in local circumstances (e.g. changes in availability of reagents or equipment).

Quality control of a test method (technical quality)

Methods for the control of various haematology tests are described in Chapter 25 but some may need to be adapted to specific local circumstances in resource-poor settings. For example, if commercial controls for sickle cell tests are not affordable, each batch of tests should include known positive and negative samples from a previous batch of tests; for monitoring constancy of Hb measurements, a high and a low value sample can be retested several times during the day.

Internal quality control

Internal quality control is a system within an individual laboratory for ensuring that the technical elements of the test are of acceptable quality. Monitoring of quality by processing control samples and plotting a control chart (see p. 539) will highlight problems within the system which need to be investigated and corrected. For example, an inaccurate differential white cell count may be due to problems with sample collection and handling, slide preparation, fixing and staining, morphological interpretation and microscope quality as well as inadequate microscopy technique. Measures such as the introduction of SOPs, in-service training and equipment maintenance schedules can help to improve performance and reduce inaccuracies.

You're Reading a Preview

Become a Clinical Tree membership for Full access and enjoy Unlimited articles

Become membership

If you are a member. Log in here