Investigations, Investigations, Investigations (Part 4)

Image courtesy of [anankkml] / FreeDigitalPhotos.net

The cornerstone of medicine remains the classic history and examination- let the patient tell their story, and the physician's hand of assessment can help pinpoint the diagnosis.

However, when diagnoses are unclear or can't be differentiated, that's where investigations come in. Sadly, today they're often over-used, but when used appropriately they offer a wealth of information that can help tailor all important management and get the patient on the path to recovery faster.

Following on from part one, where we looked at urine, part two which look at bloods, and part three which looked at imaging, this multi-part post will take a look at some of the common investigations performed, what they can tell us and the reasons why and when they should be used.

Our fourth and final part deals with some other tests that didn't fit into the above categories, but which are as important in assessing patients and helping to reach a diagnosis.

Part Four- Everything Else!

ECG/ 24hr tape/ exercise ECG

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An ECG (or EKG, electrocardiogram) looks at the electrical activity in the heart. While heart muscle beats on its own, it needs nerve activity to set things like rate (how fast it's beating) and contractility (how hard it beats). ECGs are actually extremely useful and can give a lot of information outside of just seeing the heart rhythm. We can do standard 12-lead ECGs, giving us an indication of what the heart is doing now, or 24hr tapes, where a holter is worn for 24hrs and the heart rate recorded continuously. This is often good to pick up abnormal heart rates associated with palpitations.

It's mostly used to detect arrhythmias (abnormal heart beats, such as atrial fibrillation (irregular pulse), supraventricular tachycardias (too fast), heart block and bradycardias (too slow), and 'missed' beats), but it can also look for cardiac disease (ischaemic heart disease or full blown myocardial infarction [heart attack], heart infections (pericarditis), heart enlargement, and in the case of heart failure it can even give us prognosis (how severe the heart failure is and the outcome of this). It can also pick up problems with the lungs, such as in pulmonary embolism, which can cause strain on the right chambers of the heart.

However, having a normal ECG doesn't rule out there's a problem with the heart, so it's not got a very good negative predictive value. Nevertheless it's an extremely useful tool in practice.

Further reading:

1. http://www.patient.co.uk/health/electrocardiogram-ecg

2. http://www.bhf.org.uk/heart-health/tests/ecg.aspx

24hr BP monitoring

Image courtesy of [photostock] / FreeDigitalPhotos.net

Whenever we visit the doctors for a blood pressure check, it's always high, right? But how can we tell it's because of 'whitecoat hypertension' (the BP goes up because you're stressed about seeing a doctor), or actual 'essential hypertension'? We measure BP over 24 hours, of course. This has become the standard for diagnosing true hypertension and helps to plan what treatments to start on.

The patient is given the machine to take home, and the monitor takes several readings through the day and night. If the overall average value and night values are above the limit, then we can start treatment. Not only is this test more accurate than measuring BP at single points on different days, it saves on the patient having to keep returning to have BP checks for diagnosis.

Some problems with this test though are that some patients can't tolerate it, and the fact that the machine needs to be loaned out. It also needs a patient to be aware of how to use it (so for example it could be difficult to perform in a frail elderly person requiring a lot of care).

1. http://www.bloodpressureuk.org/BloodPressureandyou/Medicaltests/24-hourtest

Pulse dopplers and ABPI

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A doppler machine works on a similar principle to ultrasound, except instead of projecting images, it projects sound. This can be very useful in looking at blood flow through arteries, as blood makes sound as it flows. We can measure this while changing blood flow as well via a blood pressure cuff, and hence we can give a ratio of how good the circulation is at the hands and feet. This is known as an 'ankle brachial pressure index', where we compare blood flow in the arm and leg at a given pressure. The lower this number is, the more likely it is you have severe circulation problems in the leg, which can lead to complications.

It's also used a lot in pregnancy, as we can detect the fetal heartbeat from around 14-16 weeks onwards, and is useful to check fetal wellbeing if the mother is experiencing problems.

However, the problem with this test are that it can give false readings (as patients with diabetes might have normal ABPIs but still have poor circulation), and it needs special training to be performed.

Further reading:

1. http://www.webmd.com/dvt/doppler-ultrasound

2. http://www.westcoastvascular.com.au/services/doppler-test/

Nerve conduction studies

Image courtesy of [renjith krishnan] / FreeDigitalPhotos.net

We also have the means to measure how well nerves transmit sensation and information! These are called nerve conduction studies and are very specialised. We measure the current running through a specific nerve (such as the median nerve in the wrist), and the speed and amplitude tells us whether there is any nerve damage. We can also do this following trauma or fracture and the patient still complains of nerve symptoms (tingling/ pins and needles/ numbness) following resolution of the original injury.

This test is necessary for a confirmation of a diagnosis of carpal tunnel syndrome before any surgery is planned. This is to also have documentation of nerve function pre-surgery, so that we know if the damage was there before anything was done.

The drawbacks are that it can be an unpleasant procedure (as needles are used to look at nerve function in specific muscles when testing for motor problems), it's very time consuming, and it needs specially trained neurophysiologists to perform.

Further reading:

1. http://www.patient.co.uk/health/nerve-conduction-studies

2. http://drprafullkdavemd.com/ncs.php

Electroenecephalogram (EEG)

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Electroencephalograms are similar in principle to the ECG/EKG, except these look at the electrial activity in the brain. This is often done to look for epilepsy. They can also be co-ordinated with video to look at what the EEG does if the patient has a seizure. However, they can be very difficult to interpret, and like with ECGs, having a normal EEG doesn't mean there's nothing wrong. Yet as with most tests, it needs to be interpretted in the clinical context to be of diagnostic value.

Further reading:

1. http://www.nhs.uk/Conditions/EEG/Pages/Introduction.aspx

Spirometry

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This is a breathing test that looks at the capacity and function of the lungs. It can be used to diagnose a variety of lung diseases such as asthma, COPD, and fibrotic lung disease. It's also good as a monitoring test to see if there is improvement/ worsening of lung function over time and before/ after a course of treatment. The patient is told to breath into a tube which measures air flow. By taking big breaths and breathing out quickly, we can then get measurements of lung capacity and volume, normal breathing volume, and how fast the patient can expel air from their lungs.

However it's a very time consuming test and does rely on accurate patient performance. It's also difficult to do in young children, as they might not understand instructions.

Further reading:

1. http://www.patient.co.uk/health/spirometry-leaflet

Angiography/ colonscopy/ arthroscopy

These can be both diagnostic and therapeutic tests, meaning that it can diagnose a problem and treat it at the same time. We'll take them individually.

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Angiography looks at the blood vessels, typically of the heart, but they can look at any artery (the picture above shows the arteries of the brain). For the former, a catheter  is placed in an artery at the wrist or groin, and dye injected. X-ray images are then taken at the same time, giving us a live 'snapshot' of blood flow through the coronary arteries. If there is any obstruction, from a plaque for example, then a stent can also be placed to remove the obstruction and improve cardiac blood flow, lessening symptoms of chest pain/ angina etc. The same principle is used for other vessels, such as looking in the limbs, again for obstruction or aneurysms.

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Colonscopy is using a fibre-optic camera to have a direct look at the bowel. This is the same for any 'scopy' test- so arthroscopy is putting a camera into a joint such as the knee, nasendoscopy gives a direct look at the nasal airways/ throat, endoscopy looks at the oesophagus (food pipe) and stomach. If any abnormalities are seen, instruments can be inserted in the fibre-optic tube and biopsies (tissue samples) can be taken. In some cases treatment can be done as well, such as removing small polyps from the bowel, injecting stomach ulcers, or washing out/ trimming cartilage in joints.

The major drawback in these tests are that they are very invasive, and have small but significant complications and risks. They also need to be performed by specialists in hospital, and this might require overnight hospital stays. Also, anything needing extensive treatment, like joint replacement/ multiple blocked arteries/ multiple polyps in the bowel can't be treated.

Further reading:

1. http://www.nhs.uk/conditions/angiography/Pages/Introduction.aspx

2. http://www.patient.co.uk/health/colonoscopy

3. http://www.nhs.uk/conditions/arthroscopy/pages/introduction.aspx

Sleep studies

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This is where patients are checked for problems with oxygen levels in the blood at night during sleep. The most common reason for this is obstructive sleep apnoea, where breathing can pause for a number of seconds during sleep, leading to a decline in blood oxygen levels. This leads to daytime sleepiness and poor concentration. In this test, the patient wears an oxygen monitor, and any 'dips' are recorded. Other parameters can be measured such as heart rate, blood pressure and body movement. If the pattern meets the diagnostic criteria, then a formal diagnosis can be made and suitable treatments tried, such as a positive air pressure machine.

Further reading:


1. http://www.nhs.uk/Conditions/Sleep-apnoea/Pages/diagnosis.aspx

2. http://www.ucmc150.uchicago.edu/sleep/studies.html

So that's my whistle stop tour of the major investigations available to use today! I hope you found it informative.

Investigations, Investigations, Investigations (Part 3)

Image courtesy of [anankkml] / FreeDigitalPhotos.net

The cornerstone of medicine remains the classic history and examination- let the patient tell their story, and the physician's hand of assessment can help pinpoint the diagnosis.

However, when diagnoses are unclear or can't be differentiated, that's where investigations come in. Sadly, today they're often over-used, but when used appropriately they offer a wealth of information that can help tailor all important management and get the patient on the path to recovery faster.

Following on from part one, where we looked at urine, and part two which look at bloods, this multi-part post will take a look at some of the common investigations performed, what they can tell us and the reasons why and when they should be used.

Part three deals with one of the more extravagant tests doctors can use- the various imaging that can visualise our internal anatomy.

Part Three- Imaging

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A picture paints a thousand words, yes? Or a scan can reveal things that other tests can't. Scans are a double-edged sword, however, in that they required skilled interpretation, and some things seen on a scan may have nothing to do with the symptoms the patient is experiencing. This is why scans are often rationed, and radiologists need a good clinical history to correlate what they see to what the patient feels.

It can be frustrating for patients who often feel the doctor they see should review their scans in front of them, but while we're competent to look at simple X-rays, we're only taught at a basic level to recognise barn-door obvious things in the more complex scans such as CT/ CAT, MRI and ultrasound. This is why the specialty of radiology exists, as they see hundreds of thousands of these scans and thus are much better to analyse more subtle changes.

So let's delve into the types of imaging available to us today:

-X rays

The humble X-ray still has plenty of uses today, from finding bone fractures to looking for chest infections or heart failure. Every doctor, radiologist or not, usually knows how to interpret an X-ray. Of course, the drawback is the radiation risk, which while it's extremely low and is generally very very safe, it can't be used in some situations like pregnancy. Still, it remains a very useful test.

The other drawback to X-rays is that they are a 2D image of a 3D structure, so you can miss things (like lung cancers that are behind the heart shadow), and it can be difficult to visualise structures. This is where CT comes in...

-CT scan

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Computed tomography, or computed axial tomography (CAT), is a step up from X-rays in that we can use it to picture the body in three dimensions and not two. The radiation dose is quite a step up, too, so again this imaging can't be used for everything, and certainly not in certain situations. It is excellent at assessing fractures, head injuries or brain pathology like stroke, looking at intra-abdominal organs (like liver, bowel, spleen, kidneys etc) and assessing spread of cancers. When used with contrast, it can also pick up blood clots in the lung or arterial dissections.

CT scans have become much more widely used, particularly by surgeons, as it allows them to visualise the organs in the abdomen without having to lay a scalpel on the patient and all the risks of laparotomy (open abdominal surgery), and hence they can plan surgery and hopefully account for otherwise unseen risks.

However, as it's based on X-rays, CTs are not so good for looking at soft tissues and can't see subtle changes. This is where the next imagine modality steps in...

-Magnetic Resonance Imaging (MRI)

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This, as the name suggests, is based on magnets, and the alignment of water molecules. This allows for very detailed imaging of soft tissues, and hence MRI is the best for brain scans (showing subtle changes, such as old strokes or demyelination, which can be a sign of multiple sclerosis), scans to look at spread of tumours in the pelvis/ neck, and spinal scans to look for spinal cord compression. There's also no radiation risk, either.

However, MRIs are complex, and not a pleasant experience. Patients need to be still for a long period of time (making it harder to scan children without sedating them), MRIs are slow, and also they can pick up totally insignificant things that may not correlate to symptoms, but we can't tell that.

Spin-offs of MRI include MRAs (magnetic resonance arteriograms, which look at the arteries specifically).

-Ultrasound

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Perhaps one of the safest imaging modalities, ultrasound has many uses, not just in pregnancy (as pictured above). It can assess abdominal and pelvic organs, look at complex joints such as the shoulder, help guide doctors to insert drains or central lines, it can assess lumps and bumps, and can help guide radiologist to take samples of said lumps (ultrasound guided biopsies or fine needle aspirations). It can even assess the heart, including the valves, the muscle wall, and how effective it's pumping blood. Best of all, there is no radiation risk. Sounds like the best of the lot, right?

However, as with all these imaging modalities, it does have its limits. The major one is that it can be very operator specific- that is, different ultrasonographers can interpret their findings differently. Also, things can get in the way, such as bowel gas, which can obscure the image, and with patients with a high BMI, it can be difficult to see, too.

Whew, so that's imaging! Oddly enough, there hasn't really been much change in the last few years, but who knows what the future will bring us...

The next and final part of this series will look at the leftovers, such as ECGs, 24hr tapes and the like.

Part 1- Urine

Part 2- Bloods

Lisa's Summer Reads Blog Tour 2014- A.F.E. Smith

Summer Reads Blog Tour - Week Ten A.F.E. Smith

Reblogged from lisawiedmeier.com. This summer she's hosting a fantastic summer reads blog tour, where authors get to share their favourite reads! So you might just find your next favourite book. She's also hosting a fab giveaway with some awesome prizes, so enter to win (link at the bottom of the post).

Drum roll please as we're already into week ten of our Summer Reads Blog Tour, and welcome A.F.E. Smith!

My name is A.F.E. Smith and I can usually be found online in the form of a robin. But I've been categorically told that I have to include a picture of my real face for this blog tour, so here it is ...

In human form, I work as an editor and also as a parent, and squeeze writing in around the edges. (My son is two and I have a daughter on the way, so the edges are pretty squeezed.) Things I like include snacks, books, complex maths problems, snacks, animated films and snacks. My debut novel, DARKHAVEN, is coming soon as an ebook from Harper Voyager.

It's a fast-paced fantasy whodunnit featuring love, murder and obsession, carriage chases, duels to the death and a very angry Wyvern, set in a unique city in the throes of industrial revolution. Here's a little bit more about it: Myrren Nightshade has been overlord of Darkhaven for less than a day, and already he has a brutal murder to deal with. Not just any murder, either. His father is the victim – and his sister Ayla is the only suspect. Born without the shapeshifting abilities specific to his bloodline, Myrren has always considered himself inadequate. But now it's up to him to prove his sister innocent before the law finds her guilty. Aided by a reluctant priestess, and hampered by a Captain of the Helm determined to block him at every turn, Myrren must navigate his way through a maze of secrets and lies to the truth at the centre – even if it could destroy him. Meanwhile, Ayla Nightshade has problems of her own. Fleeing from the threat of incarceration for a crime she didn't commit, unable to take refuge in her other form, she is alone and friendless. The only person willing to offer her aid is the man she despises above all others: the man she holds responsible for her mother's death.

If you'd like to know more about me or my work, here are a few links:

Website

Facebook

Twitter

Goodreads

And now for the most important part – my book recommendations! As a fantasy reader/writer, I've gone for books that have at least an element of fantasy to them. You may not have come across these books before, but they all deserve more readers. I keep my five-star ratings for books I've loved enough to read more than once, but I'm pretty sure all five of the following books will join that number someday ...

A.F.E.'s bookshelf: summer-reads-blog-2014

The Traitor Game

by B.R. Collins

This is a super-intense YA novel that explores a serious theme (bullying) in the real world as well as creating a fascinating parallel fantasy world. The two strands are well constructed and cleverly interwoven. Recommended for teens and...

Zero Sum Game

by SL Huang

I kind of wish I had written this book myself, given that it features a female protagonist whose superpower is being really good at maths. It's also full of action, well written and just plain awesome. Looking forward to the next in the ...

Few Are Chosen

by M.T. McGuire

This is comic fantasy, but like all the best comedy, it has a heart. By the end of the book, I defy you not to want to read the other three books in the trilogy (yes, in true Douglas Adams style this is a trilogy of four) to find out wha...

The City's Son

by Tom Pollock

Urban fantasy in the truest sense of the phrase. The author's alternate London is consistently imaginative and inventive. Aimed at a YA audience but great for adults too, this book is for anyone who likes to be immersed in the familiar-y...

The Golem and the Jinni

by Helene Wecker

A wonderful and atmospheric book, drawing on the mythology of two different cultures to create something new. It's a romance and a fantasy and a fairytale, yet at the same time it vividly brings to life the experiences of immigrants in t...

a Rafflecopter giveaway

Investigations, Investigations, Investigations (Part 2)

Image courtesy of [anankkml] / FreeDigitalPhotos.net

The cornerstone of medicine remains the classic history and examination- let the patient tell their story, and the physician's hand of assessment can help pinpoint the diagnosis.

However, when diagnoses are unclear or can't be differentiated, that's where investigations come in. Sadly, today they're often over-used, but when used appropriately they offer a wealth of information that can help tailor all important management and get the patient on the path to recovery faster.

Following on from part one, where we looked at urine, this multi-part post will take a look at some of the common investigations performed, what they can tell us and the reasons why and when they should be used. Part two deals with perhaps one of the most important investigations available to modern medicine- blood!

Perhaps one of the most loathed tests for patients, as it involves needles, blood is an amazingly versatile substance, and it can tell us a lot about a patient.

PART 2- blood

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Today we have thousands of blood tests that can check for almost anything in terms of pathology, from inflammatory markers to vitamin and drug levels, to autoimmune conditions, kidney and liver function, and even whether you've had a heart attack or not.

It would be impossible for me to go through every single one, so I'm going to stick to the routine tests performed.

Note that I've not included reference ranges here, as many hospital use different machines which have different units, and it can be confusing.

Depending on what it's used for, blood needs to be taken in various different coloured bottles, as different reagents are needed to identify the compounds.

Full Blood Count (Complete Blood Count)

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This test assesses various blood components that come from the bone marrow. This includes haemoglobin (Hb), the molecule that carries oxygen in the blood; white cells (WCC, white cell count), the fighting force that give immunity to infection; platelets, the tiny fragments that stop bleeding, and lots of other smaller parameters that can all be useful.

Hb checks for anaemia (too little) or polycythaemia (too much), and in conjunction with other parameters (like red cell volume, mean cell volume) can also point to the cause (e.g. microcytic anaemia could be due to iron deficiency).

The WCC, if low, can indicate immunosuppression or bone marrow failure, or if high, acute infection or inflammation, or if very very high, leukaemia.

Finally, the platelets can give an indication of clotting ability and bleeding or thrombotic risk (e.g. low platelets, thrombocytopenia, can increase risk of bleeding, but too high platelets, thrombocythaemia, increase risk of clots in the body, including the coronary vessels of the heart, leading to a heart attck)

All in all, the FBC/CBC an extremely useful test for many different pathologies, and hence why it's included in the routine blood tests.

Biochemistry

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This is a broad term that includes:

- Urea and Electrolytes, looking at how the kidneys function, the concentration of important blood salts such as sodium and potassium, and how much kidney reserve you have.

- Liver function, looking at various liver enzymes, and how the liver functions. Specific liver enzyme increases can even tell us what's causing the problem, such as gallstones, alcoholic liver disease, or hepatitis. And even if the diagnosis is unclear, we can then use other tests like ultrasound to guide us.

- CRP (C-reactive protein). This is a non-specific marker of infection or inflammation. As such, when it's raised, it's not that helpful at all as any number of things can cause this, but when it's normal, it can help rule out serious infections, and if you repeat the test, we can also see if treatment is working (it should decrease). Some hospitals don't bother with it though, as it's so unspecific.

-Albumin and protein. Again these also act as markers of liver and renal function (if low, it means the liver's manufacturing capability is poor due to damage, or it could mean the kidneys have lost their filtering ability and all the protein is being excreted into the urine). We can also identify if there are any nutrition or absorption problems from the gut. If abnormally high, this can also be a sign of multiple myeloma. However, like with CRP, it's not a very specific test and so it needs to be read in the context of other results and the patient's symptoms.

- Lactate. This is a marker of anaerobic respiration in the body. Why is this important? Well, our cells need oxygen to survive, and normally use oxygen in aerobic respiration to create energy. But in oxygen starved states (such as running a marathon, or if you've got a severe chest infection), the body is so low in oxygen it needs to convert to a non-oxygen means of making energy. It's not good to have lactate in high concentrations for a prolonged period, and it's a good marker to look at the severity of an acute illness where the body is severely starved of oxygen (such as chest infections, sepsis, major heart attack etc).

- Hormone profiles include the thyroid hormones (thyroid stimulating hormone, TSH, T4 and T3), the female and male sex hormones such as oestrogen, progesterone, testosterone, FSH [follicle stimulating hormone] and LH (luteinising horming], prolactin [important in breast feeding and benign tumours of the pituitary], cortisol [natural steroid]). These are important for endocrine problems.

-Glucose and HbA1c are useful for diagnosing and monitoring diabetes. HbA1c is 'glycosylated haemoglobin'. The premise of this test is to look at long term diabetic control. It works because it's measuring the amount of glucose that has stuck to part of the haemaglobin we talked about earlier. As the life span of a red cell (where the haemaglobin is) is about 90 days, we can therefore see that the higher the amount of glucose stuck to the cell, the higher the blood sugar has been over those 90 days. Targeting the HbA1c can be useful to prevent or reduce the risk of diabetic complications.

-Drug levels. Digoxin, lithium, sodium valproate, pheyntoin, aspirin, paracetamol (acitomenophen) and many other drugs can also be measured, either in terms of acute poisoning or overdose, or to monitor safe dosing and compliance to treatment.

- Cardiac Troponins. These tiny protein molecules are release when the heart muscle (myocardium) is damaged, and can be a great indicator if there has been heart muscle damage, either from a heart attack, atrial fibrillation or infection. While they are pretty specific for this, note that some conditions like chronic renal failure, pulmonary embolism and others can cause a 'false' high level, so interpret with caution.

Clotting

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This looks at the clotting factors produced by the liver (which work in conjunction with platelets to stop bleeding). If these are abnormal, it can be an indicator of liver disease or severe infection.

The INR (international normalised ratio) is also used as a standardized marker for warfarin therapy, which is used in the treatment of blood clots (thromboembolism) and in prevention of formation of clots.

The APTT (activated partial thromboplastin time) is used to monitor heparin therapy.

Like with liver function, patterns of clotting abnormality can pinpoint the diagnosis. We can also test for some specific clotting factors (like factor 8, which is affected in haemophilia), which can help exclude or confirm diagnosis.

Group and Save/ Cross Match

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This is used for patients requiring or who may require a blood transfusion, either as an emergency (cross match, the sample is processed very quickly but it's only basic type specific blood) or after an elective operation (group and save, processed more slowly but more type specific blood is issued). This test must be repeated after a transfusion is given, as a patient may develop antibodies and so different blood needs to be matched to prevent an immune reaction.

Immunology Testing

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These highly expensive and non-routine tests look for antibodies, typically those causing autoimmune conditions like rhematoid arthritis These tend to be quite specialised and need to be interpreted in a clinical context. Alone they are quite useless, as the results are given in titres, not absolutes, and have a wide interpretation.

Examples include rheumatoid factor (RF), although you CAN have RA with a negative RF), anti-neutrophil antibody (ANA), anti-double strand DNA (specific for systemic lupus erythematosis, SLE) anti-Ro, anti-La (it's like a piano song isn't it?), and many more.

- Serology. This looks at antibodies against infection, such as rubella, chicken pox, and others. More complex testing is done for things like HIV and Hepatitis B. This helps us to see if a patient has had a previous infection to this disease, is having a current infection, and if they have immunity. This is also used for to check that a vaccine (typically Hepatitis B) has worked.

Whew, that was a lot of blood tests, and there's still so many more I haven't covered!

Part 3 will move onto another very common set of testing- images.


Further reading:

1. http://www.nhs.uk/conditions/blood-tests/pages/introduction.aspx