No formalin please, it could be TB!
Historically, tuberculosis (TB) in the UK was primarily associated
with pulmonary infection. However, as the rates of TB in the UK have
risen, so has the proportion of extra pulmonary disease. In 1987, the
total number of new TB cases was 5,085 and 21% of these were extra
pulmonary. By 2009, the annual number of TB cases had risen to 9,040
with 46% being extra pulmonary (HPA 2010).
KEYWORDS Tuberculosis / TB diagnosis / Formalin / Surgical samples / TB microbiology
Tuberculosis (Care and treatment)
Drug resistance (Research)
|Publication:||Name: Journal of Perioperative Practice Publisher: Association for Perioperative Practice Audience: Academic Format: Magazine/Journal Subject: Health; Health care industry Copyright: COPYRIGHT 2011 Association for Perioperative Practice ISSN: 1750-4589|
|Issue:||Date: July, 2011 Source Volume: 21 Source Issue: 7|
|Topic:||Event Code: 310 Science & research|
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|Geographic:||Geographic Scope: United Kingdom Geographic Code: 4EUUK United Kingdom|
Extra pulmonary TB can affect any part of the body including the
lymph nodes, GI and genitourinary systems, bones and joints, central
nervous system, skin, pericardium and disseminated infection (Ormerod
In 2004, the Department of Health set a national target to confirm 65% of TB diagnoses through microbiological culture (DH 2004). To achieve this, NICE (2006) recommended that, if TB is suspected (see Box 1 for signs and symptoms of TB) or if the patient falls into a high risk group (see Box 2), part of their surgical sample should be placed into a dry pot (not in formalin) and sent to microbiology for TB culture.
Why is TB culture so important?
Without microbiological confirmation of TB, it is impossible to differentiate between Mycobacterium tuberculosis and the nontuberculous mycobacteria species (BTS 1999). All species of mycobacteria can cause disease in humans, but they require different treatment regimens. Only Mycobacterium tuberculosis complex is notifiable under public health law and no contact tracing is required when a patient is diagnosed with a non-tuberculous mycobacteria infection (BTS 1999).
This is of particular relevance to those involved in perioperative practice especially those requesting, obtaining and sending specimens for histology and microbiology investigations.
When and how should a sample be sent for TB culture?
NICE (2006) guidelines state that if extra-pulmonary TB is a possibility, part or all of any of the following samples should be placed in a dry pot (and not in formalin) and sent for TB culture (see Box 3).
The microbiology tests required are acid fast bacilli (AFB) smear and culture. TB microscopy (smear) will identify whether TB bacilli are visible under the microscope, but the species and drug sensitivities can only be identified through culture growth of the mycobacteria.
NICE (2006) also recommended that microbiology staff should routinely perform a TB culture on the above samples even if it was not requested. Locally, to prevent this extra work overwhelming the microbiology services, when TB is unlikely, it is recommended that samples should still be submitted for holding. The sample will not be processed unless the clinical picture or histology later raises the suspicion of TB.
It is vital that histology pots containing formalin are not used for samples sent to microbiology, as this will sterilise any bacteria present thereby preventing culture growth and a definitive diagnosis. The clinician therefore may need to acquire a sufficiently sized sample that can be split, with half submitted to histology and half to microbiology.
Local practice and raising awareness
To investigate local compliance with the Department of Health target, a retrospective case-note analysis of 59 patients treated for all forms of TB over a five-year period (2001-2005) was carried out. The results demonstrated that, despite the presence of at least one major TB risk factor, a high proportion (44.7% n=26) of surgical samples were not sent for TB culture. TB risk factors would include TB signs and symptoms, or the patient's origins being from a high risk group.
A targeted awareness letter promoting NICE TB guidance was designed and sent to key clinical teams across two acute hospital trusts, and the effect of this was measured by a second case-note analysis of a further 61 patients over the subsequent 3-year period 2006-2009 (Thomas et al 2009).
Prior to the distribution of the awareness letter, 55.3 % (n=26) of patients had samples correctly sent for TB culture. After the awareness campaign, the percentage significantly increased to 73.4% (n=36, p=0.002). Clinicians not requesting TB culture (41%, n=34) and/or the use of formalin to fix samples (62%, n=22) were the two main reasons preventing TB culture. Clinical teams not targeted with the letter did not demonstrate any improvement (p=1.0)
The numbers and proportion of extra pulmonary TB cases continue to rise in the UK. This means that a greater number of clinical specialities are being involved in the initial collection of samples for diagnosis.
This small scale study demonstrated that national standards for TB diagnosis can be met by increasing awareness that samples should be submitted to microbiology. Raising awareness of TB symptoms and high risk groups is the first step, but this must be complemented by an increase in the number of samples being submitted for TB culture and the knowledge that samples must never be placed into pots containing formalin.
We would urge all those involved in sample collection to consider TB as a potential diagnosis and to ensure that samples are correctly submitted to microbiology. Theatre managers or department heads could consider amending standard operating procedures to reflect this.
No competing interests declared
Provenance and Peer review: Commissioned by the Editor; Peer reviewed; Accepted for publication April 2011.
Breen R, Leonard O, Perrin F et al 2008 How good are systemic symptoms and blood inflammatory markers at detecting individuals with tuberculosis? The International Journal of Tuberculosis and Lung Disease 12 (1) 44-49
British Thoracic Society (Joint Tuberculosis Committee) 1999 Management of opportunist mycobacterial infections Thorax 55 210-218
Davies P 2003 Clinical tuberculosis 3rd edition London, Hodder Arnold
Department of Health 2004 Stopping tuberculosis in England. An action plan from the chief medical officer London, DH
Health Protection Agency 2010 Tuberculosis in the UK: Annual report on tuberculosis surveillance in the UK 2010 London, HPA Centre for Infections
National Institute for Health and Clinical Excellence 2006 Tuberculosis: clinical diagnosis and management of tuberculosis, and measures for its prevention and control London, NICE
Ormerod P 2008 Non Respiratory Tuberculosis In: Davies P, Barnes P, Gordon S (Eds) Clinical Tuberculosis 4th edition London, Hodder Arnold
Pratt R, Grange J, Williams V 2005 Tuberculosis: A Foundation for Nursing and Health Care Practice London, Hodder Education
Thomas D, Jarvis M, Williams A 2009 Challenging traditional practice can increase the microbiological diagnosis of tuberculosis from surgically acquired samples. Presented at the British Thoracic Society Winter meeting Thorax Suppl IV 64 A125
Provenance and Peer review: Commissioned by the editor;
Correspondence address: David Thomas, East Dorset TB Service, Department of Thoracic Medicine, Royal Bournemouth Hospital, Castle Lane East, Bournemouth, BH7 7DW.
About the authors
David Thomas BSc, Dip Nursing Sci, Trop Nurse, RN
Lead TB Specialist Nurse, East Dorset TB Service, Department of Thoracic Medicine, Royal Bournemouth Hospital, Bournemouth
Miles Jarvis MA, BSc (Hons), Dip HE, Dip Trop Nurse, RN
TB Specialist Nurse, East Dorset TB Service, Department of Thoracic Medicine, Royal Bournemouth Hospital, Bournemouth
Alan Williams MD, FRCP
Consultant Physician, Department of Thoracic Medicine, Royal Bournemouth Hospital, Bournemouth
Box 1 Common signs and symptoms of tuberculosis (Davies 2003) The following are signs and symptoms that would be suggestive of an active TB infection: * Cough for more than three weeks, with or without sputum production * Loss of appetite * Weight loss * Night sweats * Lethargy * Lymphadenopathy * Pyrexia of unknown origin * Haemoptysis * Other focal signs and symptoms dependant on the site of disease It is important to note that not all patients will present with the above symptoms. Breen et al (2008) found that 25% of patients were not complaining of three of the most important symptoms, yet had an active TB infection. TB patients may present with localised lymphadenopathy being the only symptom. Box 2 High risk groups for tuberculosis (Pratt et al 2005) * New immigrants from countries with high rates of TB * Those with HIV infection * Those with a history of IV or heavy drug/alcohol abuse * Prison populations * Homeless * Patients who are immunosuppressed * Refugees/displaced populations * Ethnic minorities/marginalised groups * Those with occupational exposure
Box 3 Samples for microbiological TB culture (NICE 2006) * Lymph node biopsy * Pus aspirated from lymph nodes * Pleural biopsy * Any surgical sample sent for routine culture * Any radiological sample sent for routine culture * Histology samples * Aspiration samples * Autopsy samples
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