| Course | PA 502 Evidence Based Medicine |
|---|---|
| Week | 4 |
| Paper type | Surrogate outcome critique |
| Length | About 1,100 words, 5 pages |
| Format | APA 7 student paper |
| School | Chamberlain University |
| Program | Master of Physician Assistant Studies (MPAS) |
| Updated | October 2026 |
Free sample paper for PA 502 Week 4
Surrogate Outcome Critique: When a Lower Systolic Reading Stands In for Fewer Strokes, Heart Attacks and Deaths, and Where the Chain Held and Broke in Two Trials
Student Name
Chamberlain University
PA 502: Evidence Based Medicine
Instructor Name
Month Day, Year
Surrogate Outcome Critique: When a Lower Systolic Reading Stands In for Fewer Strokes, Heart Attacks and Deaths, and Where the Chain Held and Broke in Two Trials
The Pair, Written Down First
The surrogate here is the systolic blood pressure reading, the number a clinic records. The outcomes it stands in for are the events a person would notice: a stroke, a heart attack, heart failure and death. When a clinician says a patient's blood pressure should be lower, the claim is really that lowering the number will prevent those events. This critique examines whether that claim held in two trials that pushed the number to about 120 mm Hg, one in people without diabetes and one in people with it.
The Chain, Marked One Link at a Time
The chain from surrogate to outcome has three links. First, treatment lowers the systolic reading. Second, a lower reading reduces strain on the heart and damage to blood vessels in the brain, heart and kidneys. Third, less strain and damage means fewer strokes, heart attacks and deaths. Each link can hold or break. The first link held in both trials: in SPRINT, mean systolic pressure at one year was 121.4 mm Hg with the intensive target and 136.2 mm Hg with the standard target (SPRINT Research Group, 2015); in the ACCORD blood pressure trial, it was 119.3 mm Hg and 133.5 mm Hg (ACCORD Study Group, 2010). The question is whether the later links held.
Where the Chain Held: SPRINT
In SPRINT, among 9,361 people at increased cardiovascular risk without diabetes, the lower reading was followed by fewer events. The primary composite outcome occurred at 1.65% a year with the intensive target and 2.19% a year with the standard target, a hazard ratio of 0.75, and all-cause mortality was also lower, with a hazard ratio of 0.73 (SPRINT Research Group, 2015). Here, the surrogate pointed the right way: a lower number came with fewer of the events patients care about.
Where the Chain Broke: ACCORD
In ACCORD, among 4,733 people with type 2 diabetes at high cardiovascular risk, the same 14-point difference in systolic pressure did not significantly reduce the primary outcome of nonfatal heart attack, nonfatal stroke or cardiovascular death: 1.87% a year with the intensive target against 2.09% with the standard target, a hazard ratio of 0.88 with a 95% confidence interval of 0.73 to 1.06. Death from any cause was not lower, at 1.28% against 1.19% a year. Stroke, a secondary outcome, was lower, 0.32% against 0.53% a year. Serious adverse events attributed to treatment were more than twice as common with the intensive target, 3.3% against 1.3% (ACCORD Study Group, 2010).
So the chain held for stroke, the outcome most tightly tied to blood pressure in both physiology and in the earlier treatment trials, but did not deliver a clear reduction in the broader composite or in deaths, while harms rose.
Table 1
The Same Surrogate Change, Two Different Outcome Results
| Trial and population | Systolic at one year, intensive versus standard | Primary outcome | Deaths | Treatment-related harm |
|---|---|---|---|---|
| SPRINT, no diabetes | 121.4 versus 136.2 mm Hg | Fewer events, hazard ratio 0.75 | Fewer, hazard ratio 0.73 | More hypotension, syncope, kidney injury |
| ACCORD, type 2 diabetes | 119.3 versus 133.5 mm Hg | No significant reduction, hazard ratio 0.88 | Not reduced | Serious adverse events 3.3% versus 1.3% |
Note. Note. Figures from the SPRINT Research Group (2015) and the ACCORD Study Group (2010).
What Would License the Swap
A surrogate can stand in for an outcome only when trials show that changing the surrogate, by different means and in different populations, reliably changes the outcome by a predictable amount. Blood pressure is among the better-supported surrogates in medicine, especially for stroke. But the two trials show that the relationship is not the same in every population: in people with diabetes, a lower number did not reliably buy a lower rate of all major events. A target reached in one population cannot be assumed to bring the same benefit in another, and the lower the target, the less the general relationship can be trusted, because few trials have tested very low numbers.
How Big, Against What
Even where the surrogate held, the size of the benefit has to be judged against the patient's baseline risk. In SPRINT, the absolute difference in the primary outcome was about 1.6 percentage points over three years. A clinician who reports only that the patient's pressure fell by 15 points has reported a large change in the surrogate and said nothing about whether the patient's chance of a stroke changed by a lot or a little.
Benefit and Harm on Different Scales
Benefit and harm are also measured differently. The benefit is a reduction in events over years; the harms, such as fainting and kidney injury, arrive within weeks and are counted in the same patients. A patient deciding whether to aim lower needs both on the same scale, as events per 100 people over the same period, not a blood pressure number on one side and a list of side effects on the other.
What This Means for My Patient
My 76-year-old patient does not have diabetes, so the trial in which the chain held, SPRINT, is the closer match. The ACCORD result is a warning not to assume that a lower reading always helps, and a reason to measure outcomes the patient would notice, such as dizziness on standing, rather than the reading alone, if the target is lowered.
Why Stroke Held When the Composite Did Not
The pattern in ACCORD, fewer strokes but no clear reduction in the broader outcome, makes sense given what blood pressure does. Stroke is more closely tied to blood pressure than heart attack is, so lowering the number moves stroke risk more directly. Heart attacks depend on many other factors, such as cholesterol, smoking and, in people with diabetes, blood sugar and small-vessel disease, so a lower blood pressure alone may change them less. A surrogate is therefore strongest for the outcome it is most directly linked to. A clinician who tells a patient that lowering blood pressure prevents "heart problems" is relying on the weakest link in the chain; one who says it prevents strokes is relying on the strongest, and is giving the patient a more accurate picture. That distinction should shape how the benefit is explained.
References
ACCORD Study Group. (2010). Effects of intensive blood-pressure control in type 2 diabetes mellitus. New England Journal of Medicine, 362(17), 1575-1585. https://doi.org/10.1056/NEJMoa1001286
SPRINT Research Group. (2015). A randomized trial of intensive versus standard blood-pressure control. New England Journal of Medicine, 373(22), 2103-2116. https://doi.org/10.1056/NEJMoa1511939
The Chamberlain PA 502 Week 4 instructions
Week four asks you to critique a surrogate outcome used in clinical practice or research. Start by writing down the pair: the measure that was changed and the outcome a patient would notice. Lay out the chain of links between them and examine each one separately. Use trial evidence to show where the chain held and where it broke. Explain what kind of evidence would justify treating the surrogate as a stand-in. Compare the size of the surrogate change with the size of any change in outcomes. Put benefits and harms on the same scale. Avoid rejecting every surrogate on principle, and explain why some surrogates are better supported than others.
How this PA 502 Week 4 example is built
The critique names the systolic reading as the surrogate and strokes, heart attacks, heart failure and death as the outcomes. Three links are marked. In SPRINT, readings of 121.4 versus 136.2 came with fewer primary events, hazard ratio 0.75, and fewer deaths. In ACCORD, readings of 119.3 versus 133.5 in people with diabetes brought no significant reduction in the primary outcome, hazard ratio 0.88, no fall in deaths and more than twice the serious adverse events, though stroke fell. A table sets the two trials side by side. Sections explain why stroke held, what would license the swap and how to express benefit and harm together.
Reading the PA 502 Week 4 grading rubric
The version that loses most calls the measure a substitute and never writes down what it replaced, so the critique floats above a comparison it never makes. Next in weight is the blanket position, where every stand-in measure is refused on principle and no line explains why some are better supported. Critiques that ignore the size of the outcome change, or that present benefits as events and harms as a list, also lose points. Strong critiques write the pair first, mark each link, use trials to show where the chain held and broke, say what would justify the swap and put benefit and harm on one scale. Tying the critique back to a real patient decision shows the reader why the distinction matters at the bedside.
PA 502 Week 4 help from the desk
Surrogate outcomes are easy to criticize in general and harder to analyze link by link. If you share the surrogate your instructor assigned or one from your practice, we can help you write down the pair, lay out the chain and find trials where it held or broke. We can also help you explain why some surrogates deserve more trust than others. Your critique and conclusions remain your own. If the surrogate is a laboratory value rather than a vital sign, such as a cholesterol or glucose level, we can help you find the trials that tested whether changing it changed outcomes.
Get a PA-502 Week 4 example written to your instructions
Send the trial your section assigned together with the assignment instructions, because the chain being argued is specific to that pair of outcomes and a critique built on a different paper will not line up with what you have to submit. A custom PA-502 Week 4 critique arrives inside 24-48h and the first one is free.
More PA 502 papers and MPAS samples
- PA 502 Week 1: Clinical Question Post
- PA 502 Week 2: Bedside Question Brief
- PA 502 Week 3: NNT Calculation
- PA 502 Week 5: Applicability Write-up
- PA 502 Week 6: Guideline Comparison
- PA 502 Week 7: Decision Aid Draft
- PA 502 Week 8: Journal Club Brief
- PA 501 Week 4: Role Delineation Memo
PA 502 Week 4 questions, answered
Is a stand-in measure always a weakness?
Not always, and a flat refusal is the commonest route to a thin critique. Some measures are accepted because a body of work has shown that moving them moves the event, and a study on the event itself would take a decade and tens of thousands of people. The question is whether this particular pair has that record behind it, not whether substitution happens at all.
What if the trial reports both the measure and the real event?
Then the critique gets easier and more interesting, because both figures came out of one study and can be read against one another. Say which the paper leads with, which the study was actually sized to detect, and whether the conclusion rests on the one adequately measured. Trials sometimes move a number convincingly while the event they also counted barely shifts, and that gap is the finding.
Does the critique need sources besides the trial?
Usually two or three. One establishes what the real outcome is and why it matters to people, one covers whether the substitution has ever been validated, and one supplies a figure for the smallest change anybody would notice. Check what your section requires. A critique resting only on the trial itself has no independent ground to stand on and reads as an opinion about a paper.
Where can I find a free PA 502 Week 4 sample paper?
You can read the complete PA 502 Week 4 critique of systolic blood pressure as a surrogate, comparing SPRINT and ACCORD, on this page.
Where did the surrogate break in the PA 502 Week 4 sample?
In ACCORD, where the same drop in systolic pressure in people with diabetes did not significantly reduce the primary outcome or deaths, though strokes fell.