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The NU 611 Unit 7 diagnostic error analysis, in full
Anchoring on Muscle Strain: A Diagnostic Error Analysis of Delayed Recognition of Spinal Epidural Abscess
Student Name
Department of Nursing, Herzing University
NU 611: Clinical Decision-Making
Instructor Name
March 10, 2026
Anchoring on Muscle Strain: A Diagnostic Error Analysis of Delayed Recognition of Spinal Epidural Abscess
The Case as It Happened
This analysis uses a composite case built for teaching. Mr. P., a 49-year-old warehouse worker with type 2 diabetes, came to an urgent care clinic on a Monday reporting low back pain for four days. He said the pain started after a weekend spent moving furniture. The pain was in the midline of the lower back, constant, 7 out of 10, and worse at night. He had taken ibuprofen with little effect. The note records no fever at the visit, with a temperature of 99.5 F, and a normal neurologic examination of the legs. He was diagnosed with lumbar strain, given a muscle relaxant, and told to return if not better in one to two weeks.
Nine days later he returned to the same clinic, seen by a different clinician. The pain was now severe and he reported feeling "feverish on and off." His temperature was 100.6 F. The note records point tenderness over the L3 spinous process. Because his previous visit carried a diagnosis of strain, the triage note read "f/u back strain, not improving," and the visit was booked as a routine follow-up. He was given a stronger analgesic and referred to physical therapy.
Three days later he arrived at an emergency department with weakness in both legs and difficulty passing urine. Magnetic resonance imaging showed a lumbar spinal epidural abscess. He underwent urgent surgical decompression. At discharge he had partial recovery of leg strength, with persistent weakness in the left leg.
Outcome to Be Explained
The outcome to be explained is a delay of roughly twelve days between the first visit and diagnosis, during which the abscess progressed to neurologic deficit. Spinal epidural abscess is uncommon, and its classic triad of back pain, fever, and neurologic deficit is present in only a minority of patients at first presentation. Diagnostic delays are common: in one emergency department series, a large majority of patients with spinal epidural abscess were not diagnosed at their first visit, and patients with delays were more likely to have residual weakness (Davis et al., 2004). This background matters because it shows the first visit was a hard diagnostic problem, not an obvious miss.
What Was Knowable at Each Point
At the first visit, the knowable facts were: a plausible mechanical trigger, midline pain, pain worse at night, a temperature of 99.5 F, diabetes, and a normal neurologic examination. A reasonable clinician could have diagnosed strain. However, two features on the record did not fit strain: pain worse at night and pain not relieved by ibuprofen. Diabetes is a recognized risk factor for spinal infection. None of these made the abscess likely at that visit, but together they were grounds for a lower threshold to recheck, such as a return in 48 to 72 hours rather than one to two weeks, with specific instructions about fever.
At the second visit, the knowable facts had changed. The patient now had a recorded fever, a report of feeling feverish, point tenderness over a spinous process, and worsening pain despite treatment. Each of these is a red flag for spinal infection. This is the decision point this analysis isolates. A reasonable alternative was available: to consider infection, measure an inflammatory marker such as the erythrocyte sedimentation rate or C-reactive protein, and arrange urgent imaging. The alternative did not require hindsight; it required treating the second visit as a new presentation rather than as a follow-up.
The Reasoning Failure
The cognitive failure at the second visit was anchoring, reinforced by what Croskerry (2003) calls diagnosis momentum: a diagnostic label, once attached, gathers weight as it passes between clinicians and becomes harder to question. The evidence is in the timeline. The triage note framed the visit as a follow-up of a known diagnosis. The second clinician recorded a fever and point tenderness, which shows the data were gathered, but the plan escalated the treatment of strain rather than reopening the question. New information was read as evidence that the strain was severe rather than as evidence that it might not be strain.
Premature closure also played a part. Graber et al. (2005) found it to be the most frequent cognitive contributor to diagnostic error: the search for alternatives stops once a plausible explanation is found. At the second visit, the explanation had been found nine days earlier by someone else, and closing on it required no effort at all. This paper does not list further biases, because the timeline supports these two and no others.
System Contributors
Several system factors made the failure more likely. The triage template carried forward the previous diagnosis into the reason for visit, which framed the encounter before any clinician saw the patient. The second visit was scheduled as a short follow-up slot, which gave the clinician less time than a new-problem visit. The first visit's instructions said to return in one to two weeks without naming fever or new symptoms as reasons to return sooner, so the patient waited. No mechanism prompted a red flag review when a patient returned with the same complaint. A national report on improving diagnosis describes exactly these conditions, in which capable clinicians working inside poorly designed processes make diagnostic errors (National Academies of Sciences, Engineering, and Medicine, 2015).
A Proposed Interruption
The proposed interruption is specific and checkable: when a patient returns within 30 days with the same complaint, the visit is scheduled as a new-problem visit, and the clinician completes a three-item prompt before writing a plan. The prompt asks what the diagnosis would have to be if the original diagnosis were wrong, what has changed since the last visit, and whether any red flag for the complaint is now present, with the red flags for back pain listed on the template. The intervention can be audited by reviewing return visits for completion of the prompt and for time to imaging in patients with red flags. Singh et al. (2014) estimated that diagnostic errors affect about 1 in 20 adults in outpatient care in the United States, which makes return visits a practical place to look for them.
A second change is to the first visit's discharge instructions. Instead of a return window alone, the instructions name the findings that should bring the patient back immediately, including fever, night pain that is worsening, and weakness or numbness. This would not have prevented the first diagnosis, which was reasonable, but it would likely have shortened the interval to the second visit.
What I Change in My Own Practice
I will treat every return visit for an unimproved complaint as a new presentation and write my own differential before reading the previous diagnosis. For back pain specifically, I will document the presence or absence of fever, night pain, and immunocompromising conditions at every visit, so that a change is visible in the record. The failure in this case was reasonable at the time and still preventable, which is the reason to analyze it at all.
References
Croskerry, P. (2003). The importance of cognitive errors in diagnosis and strategies to minimize them. Academic Medicine, 78(8), 775-780. https://doi.org/10.1097/00001888-200308000-00003
Davis, D. P., Wold, R. M., Patel, R. J., Tran, A. J., Tokhi, R. N., Chan, T. C., & Vilke, G. M. (2004). The clinical presentation and impact of diagnostic delays on emergency department patients with spinal epidural abscess. Journal of Emergency Medicine, 26(3), 285-291. https://doi.org/10.1016/j.jemermed.2003.11.013
Graber, M. L., Franklin, N., & Gordon, R. (2005). Diagnostic error in internal medicine. Archives of Internal Medicine, 165(13), 1493-1499. https://doi.org/10.1001/archinte.165.13.1493
National Academies of Sciences, Engineering, and Medicine. (2015). Improving diagnosis in health care. The National Academies Press. https://doi.org/10.17226/21794
Singh, H., Meyer, A. N. D., & Thomas, E. J. (2014). The frequency of diagnostic errors in outpatient care: Estimations from three large observational studies involving US adult populations. BMJ Quality & Safety, 23(9), 727-731. https://doi.org/10.1136/bmjqs-2013-002627
What a finished NU 611 Unit 7 diagnostic error analysis looks like
The finished example is disciplined about hindsight. The case is presented as a timeline, and at each point the analysis states what was known then rather than what is known now, which is the mechanism that keeps the critique fair. The failure point is isolated to one moment where a possibility stopped being considered. The cognitive contribution is then named specifically, whether anchoring on the first impression, closing early, reaching for a recently seen diagnosis or reading later findings to confirm rather than test, and it is supported with the literature on reasoning failure. System contributors get their own treatment: handover, workload, missing prior records, interruption. The proposed interruption is concrete and checkable, and the analysis never resolves into blaming an individual.
How a NU 611 Unit 7 example is structured
The example works forward, not backward. It opens with the case laid out in sequence, with information released at the point it became available and nothing borrowed from the ending. A short section then states the outcome, so the reader knows what is being explained. The analysis isolates a single decision point and argues, from the timeline alone, that a reasonable alternative was available there. Only then is the reasoning failure named, and it is evidenced from the timeline rather than asserted from a list of biases. System factors follow with the same evidential standard, because most reasoning failures have conditions around them. The proposed interruption comes next, specific enough to be tested, and the closing section states what the writer changes in their own practice, in operational terms rather than as an intention to be careful.
The case told in real time
Information is released at the moment it became available, which is the only way to judge a decision by what the clinician could actually see.
One decision point isolated
The analysis identifies the single moment a possibility stopped being considered, rather than treating the whole encounter as uniformly flawed.
The reasoning failure evidenced
A named thinking failure is supported with lines from the timeline, since naming a bias without evidence is itself an unexamined conclusion.
System factors given their share
Handover, workload, missing records and interruption are analyzed alongside the thinking, because reasoning happens inside conditions rather than in isolation.
An interruption that could be tested
The proposed safeguard is specific enough that someone could check whether it happened, rather than an intention to think more carefully.
Where marks go in NU 611 Unit 7
This analysis loses marks whenever hindsight leaks in. Writing as though the answer was visible from the start produces a critique nobody can learn from, and faculty spot it in the first paragraph. Naming a bias without evidence from the timeline is the second failure, and listing several biases at once is a version of the same problem, since the analysis then explains nothing in particular. Blaming an individual, including yourself, replaces analysis with judgment and usually costs the professionalism criterion as well. Analyses that skip system factors miss most of what makes reasoning failures repeat. A safeguard offered as increased vigilance is the fourth leak. The strongest versions show why the failure was reasonable at the time and still preventable.
Get a NU 611 Unit 7 example written to your instructions
Send the Unit 7 instructions and the rubric from your NU 611 classroom, along with the case your section supplied or the scenario you have been asked to analyze. We write a custom example with the timeline controlled for hindsight, the failure evidenced and a testable safeguard attached, returned in 24 to 48 hours. The first custom sample is free.
NU 611 Unit 7 questions, answered
Can I write about a mistake I made myself?
Where your instructions allow it, a firsthand account often produces the strongest analysis, because you know what was actually in your head. Remove identifiers for the patient, the site and any colleague involved, and check whether your section restricts the use of real encounters. Write it as analysis rather than confession, since the criterion rewards explanation of the reasoning and not the strength of the regret.
How do I keep hindsight out of the analysis?
Build the timeline first and mark what was knowable at each point before you write a word of critique. Then argue only from what sits above the decision point. A useful test is whether a reasonable clinician with exactly that information could have made the same choice. If the answer is yes, you have located a genuine reasoning problem rather than an obvious oversight.
Does this deliverable need a real case?
Check your instructions. Many sections supply a published case or a constructed scenario, and both work, because the analysis is what is being scored rather than the source. Published safety cases have the advantage of documented timelines, which makes the real time discipline easier to hold. Whatever the source, keep clinical hours and preceptor documentation out of it, since those are your own record.