By Leya Luhar
Diagnostic reasoning has become one of the most important skills in modern pharmacy education. With prescribing reform, pharmacists are increasingly expected to interpret symptoms, assess risk, and make decisions independently.
And yet, in a UK-wide survey of over 200 pharmacy students, diagnostic reasoning was one ofthe lowest-rated prescribing-related skills in terms of student confidence. That finding does notsurprise me at all.
Diagnostic reasoning is not something you can memorise from a lecture slide or perfect through revision alone. It is a way of thinking, and like most ways of thinking in healthcare, it develops slowly and often uncomfortably.
As a medical student graduating in six months, I have spent years observing clinicians across a range of settings, from GP surgeries and community clinics to surgical wards and acute medical units. What has struck me most is not how much more they know compared to students, but how differently the same symptoms land in a clinician’s mind than they do in a student’s.
Most students rely heavily on pattern recognition. You hear a few key features in a history and instinctively try to map them onto a condition you have studied. Chest pain with sweating becomes a myocardial infarction. Dysuria and frequency become a urinary tract infection.
Lower back pain after lifting becomes mechanical back pain.
This way of thinking makes sense when you consider how we are assessed. Exam questions often push students to reach a diagnosis very early, long before a real clinician would commit toone, and they reward speed and decisiveness. Over years of exam questions, this trains students to jump quickly from symptom to label.
The problem is that real patients rarely present in neat, exam-friendly ways. Pattern recognition without depth can lead to premature closure, where you decide too early what is going on and then subconsciously ignore information that does not fit your initial impression. In real clinicalpractice, that is where mistakes happen.
What clinicians use instead are illness scripts. An illness script is not just a mental checklist ofsymptoms, but an organised package of knowledge built up through repeated exposure. It includes the type of patient who usually presents with the condition, which features make itmore or less likely, what would worry you, and what would make you rethink the diagnosis entirely.
Pattern recognition still plays a role, but it sits on top of this richer framework. When a clinician hears a symptom, they are not simply asking “what condition matches this?” They are asking whether this story fits what they expect for that illness, or whether something about it feels off.
A crucial part of clinical reasoning is knowing which features genuinely discriminate between diagnoses and which ones can be misleading. For example, if a 45-year-old woman presents with severe epigastric pain, nausea, and vomiting, your instinct may be to think of gastroenteritis, dyspepsia, or a biliary cause. But did myocardial infarction (MI) even cross your mind? MI often presents atypically in certain demographics, including women, who make up half the population. If your illness script for MI does not include this variability, you are far more likely to miss it.
I was reminded of this gap in thinking during a GP placement when a woman presented withgroin pain. My student instinct immediately went to ureteric colic or a femoral hernia. The GP, however, diagnosed osteoarthritis. I had failed to recognise the pain as joint-related because it did not match the way I had learned osteoarthritis was ‘supposed’ to present. The GP had seen this presentation many times before, and their illness script was broad enough to accommodate it.
This kind of understanding cannot be built from textbooks alone. Illness scripts are formed through clinical exposure, by taking real histories and actively trying to make sense of them rather than passively collecting information. A useful habit is to form a provisional diagnosis after a history, then check the notes and see where your reasoning aligned or diverged from that of the clinician. Over time, this sharpens your ability to recognise what matters and what does not.
One of the biggest shifts from student to clinician thinking is learning to tolerate uncertainty. In real practice, you rarely have enough information to be certain straight away, and forcing a conclusion too early is often more dangerous than sitting with ambiguity. This is directly relevant to pharmacy practice. Even when a presentation seems straightforward, your role is not just to identify the most likely explanation, but to actively consider and exclude serious alternatives that must not be missed.
Thinking like a clinician is less about confidence and more about discipline: slowing down, resisting premature labels, and asking yourself what does not quite fit. Most clinical errors begin with certainty.
(Leya Luhar is the founder of OSCE Toolbox)
