A GUIDE TO LABORATORY INVESTIGATIONS A GUIDE TO LABORATORY INVESTIGATIONS 7th edition Michael F. McGhee, Caroline A. Saxelby, and Niall McKay Seventh edition published 2022 by CRC Press 6000 Broken Sound Parkway NW, Suite 300, Boca Raton, FL 33487-2742 and by CRC Press 2 Park Square, Milton Park, Abingdon, Oxon, OX14 4RN © 2022 Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, LLC This book contains information obtained from authentic and highly regarded sources. While all reasonable efforts have been made to publish reliable data and information, neither the author[s] nor the publisher can accept any legal responsibility or liability for any errors or omis- sions that may be made. The publishers wish to make clear that any views or opinions expressed in this book by individual editors, authors or contributors are personal to them and do not nec- essarily reflect the views/opinions of the publishers. 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CONTENTS Preface vi Author Biographies viii Glossary ix Introduction xiv 1 Haematology 1 2 Microbiology 33 3 Fertility and women’s health 51 4 Rheumatology and immunology 59 5 Biochemistry 68 6 Miscellaneous 106 7 Quick reference guide for clinical scenarios 116 8 Actions following ECG automatic read-outs 127 Index 134 PREFACE TO THE SEVENTH EDITION When I entered NHS General Practice in 1981, I soon realised the benefit of a handbook to aid interpretation of the huge number of laboratory tests, often, but not always, initiated in Primary Care but being the responsibility of the GP to take appropriate follow-up actions. Many of the tests such as haematological investiga- tions remain the same after many years whilst other tests are constantly emerging. 32 years after the first edition, this useful aide memoire reference book remains as relevant as ever, not only for GP’s and practice nurses but also for any clinician needing to interpret test results. Newer investigations such as FIB-4 testing in sus- pected non-alcoholic fatty liver disease and proBNP commonly used in assessment of heart failure and transglutaminase testing for coeliac disease are now included in this revised seventh edition as well as updated guidelines for the use of HbA1c in the diagnosis and monitoring of diabetes and the FIT test (Faecal Immunochemical Test) instead of FOB testing.  After 33 years in NHS General Practice, I retired from the NHS but continue to work in Occupational Health, specifically Aviation Medicine, having served a 9-year short service commission in the Royal Air Force before entering General Practice. Whilst still dealing with clinical matters almost daily including referrals and reports from other clinicians, I still have the same need to understand the rele- vance of specific investigations, but I do not have the same access to laboratories and clinicians whom I used to rely on for advice regarding test results. I, therefore, enlisted the help of two current GP principals in practice to assist me in re-writing this edition. Dr Caroline Saxelby and Dr Niall McKay are both GPs involved in clinical practice and the teaching and training of new entrants to GP and are aware of good education in choosing and interpreting laboratory tests. Their help has been invaluable, and the book would not have continued without their help, particularly during the extremely challenging past 12 months due to Coronavi- rus. I am grateful to all clinical and non-clinical persons who have kept our health care system going during the Coronavirus epidemic and I hope that soon there is a return to the values of our NHS enjoyed and benefitted by all before Coronavirus. vii PREFACE TO THE SEVENTH EDITION Within my current field of specialism, I am now more commonly involved with abnormalities of ECGs in asymptomatic aircrew. I use well-researched and carefully considered algorithms to follow up specific abnormalities and I have chosen to share them in this edition. The section on ECG automated read-outs is not intended as a clinical interpretation for a patient presenting in General Practice with a spe- cific symptom but is a guide for what to do about common automated print-out results in asymptomatic patients with reports such as bundle branch block or con- duction disturbances. I am most grateful for the help and guidance from Dr Julia Baron BM BS MD FRCP FESC. I hope that you find the current edition useful in your daily practice. Dr Michael McGhee 21st February 2021 AUTHOR BIOGRAPHIES Dr Michael F McGhee LRCP (Lond) MRCS (Eng) MB BS (Lond) DRCOG FRCGP Cert GAM DOcc Med Mike qualified at St Mary’s Hospital London in 1975. He joined the RAF in 1972 and gained his MRCGP in 1979 and became a trainer with the RAF and spent time at The Royal Army Medical College Millbank, London with the late Professor Tommy Bouchier-Hayes RAMC. Together they organised education for military GPs in training and often engaged the help of one of the Fathers of General Practice the late John Fry CBE. Mike, after a short service commission, left the RAF to enter General Practice in Castle Donington in 1981 where he became a trainer with the Nottingham Vocational Training Scheme and an NHS appraiser. He has co-authored A Guide to General Practice, Blackwell Scientific Publications, A Guide to Infectious Diseases, Radcliffe Medical Press and Gynaecological Symptoms in Primary Care, Blackwell Science Ltd. He retired from the NHS in 2014. During his time in General Practice Mike also practised as an Aero-Medical Examiner for the UK Civil Aviation Authority. He currently works part-time at East Midlands Airport examining and certifying the fitness of Flight Crew and Air Traffic Controllers. Dr Caroline Anne Saxelby BSc (Hons) MB ChB MRCGP PGCME Caroline qualified at the University of Leeds Medical School, having previously completed a BSc in medical microbiology. She is a part-time GP in a suburban practice in Derby with a large elderly population. Her special interests are con- traception and end of life care and she currently leads on both of these areas in the practice. Since qualifying as a GP in 2008, she completed her Vocational Training in Nottingham. She has also worked as a Contraception and Sexual Health Staff doctor and was the Macmillan end of life lead for the Southern Derbyshire CCG for a number of years until 2018. She is a GP Trainer having completed her PGCME at De Montfort University, Leicester in 2010. Dr Niall McKay MB ChB (Glasgow) MRCGP (Edinburgh) Niall qualified in Glasgow in 1989. He is an experienced GP in Derby, having worked in Primary Care in Scotland, England and Australia. He is a GP trainer and Appraiser, and more recently PCN Clinical Director. GLOSSARY aCL anticardiolipin antibody ACE angiotensin-converting enzyme ACR albumin/creatinine ratio AF atrial fibrillation AFP alpha-fetoprotein AIDS acquired immune deficiency syndrome AL amyloid light-chain ALOs Actinomyces-like organisms ALP alkaline phosphatase ALT alanine transferase AKI acute kidney injury AMA antimitochondrial antibody Amp-C Amp C beta-lactamase producers ANA antinuclear antibody ANCA antineutrophil cytoplasmic antibody Anti-CCP anti-cyclic citrullinated peptide APC-R activated protein C resistance APTT activated partial thromboplastin time AS aortic stenosis ASD atrial septal defect ASO antistreptolysin-O AST aspartate transferase BMI body mass index BNP B-type natriuretic peptide BP blood pressure CAA Civil Aviation Authority CAD coronary artery disease CGIN cervical glandular intraepithelial neoplasia CHD coronary heart disease CIN cervical intra-epithelial neoplasia CK creatine kinase