4 - EBM Prognosis

7/29/2019 4 - EBM Prognosis

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CLINICAL DECISIONSUSING AN ARTICLE

ABOUT PROGNOSIS

NOEL L. ESPALLARDO, MD, MSc

Department of Clinical Epidemiology

UP College of Medicine and Philippine General Hospital


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Natural History of Disease

No With disease With disease Death

disease no symptom with symptoms

Risk Diagnosis Prognosis


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Definition of Prognosis

Prediction of the course of disease following its onset

Prognostic factorsconditions associated with theoutcome of disease

Difference with risk factors

risk factors prognostic factors

well patients diseased patients

outcome is diagnosis outcome is complication/death

rates in 1,000 or 10,000 rates 100


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A Cohort Study of Patients

with Acute MI


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No heart With heart With AMI Death

disease disease

Risk

Age

Male

Smoking

HypertensionHypercholesterolemia

Diagnosis Prognosis

Age

Female

Smoking

HypotensionAnterior infarct


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Elements of Prognostic Studies

Start of study

Zero timepoint in time in the course of disease

Inception cohortgroup of patients assembled at the onset oinception of their disease

Follow-up of study

Long enough to observe the desired outcome

End of study Five Ds death, discomfort, disease, disability and

dissatisfaction


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No heart With heart With AMI Death

disease disease

Risk Diagnosis Prognosis


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Cohort Study

With AMI Death

Start of study

Zero point

Inception cohort

Follow-up

Long enough

End

Death

Disease

Disability

DiscomfortDissatisfaction


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False Cohort

Cohort is assembled based on their availability at thetime the outcome is observed

Also termed survival cohort or available patientcohort

Presented in literature as case-series


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False Cohort Study

(Case Control)

With AMI Death

Prognostic factors Start of study

Dropout


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Potential Biases

in Cohort Studies

Sampling bias

Groups being assembled are not at similar point in time of disease

Susceptibility bias

Groups assembled are not similarly susceptible to outcome of disease

Migration bias

Some members of the group dropout of the original group

Cross-over, dropouts

Measurement

One group have less chance of determining the exact outcome


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Cohort Study

With AMI Death

Sampling bias

No clear diagnosis

Some with repeat

MI


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Effect of Sampling Bias

No With disease With disease Death

disease no symptom with symptoms

Survival A

Survival B

Test A

Test B


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Cohort Study

With AMI Death

Sampling bias

No clear diagnosis

Some with repeat

MI


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Cohort Study

With AMI Death

Sampling bias

No clear diagnosis

Some with repeat

MI

Susceptibility bias Migration bias

More with repeat MI DropoutsCrossover


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Cohort Study

With AMI Death

Sampling bias

No clear diagnosis

Some with repeat

MI

Susceptibility bias Migration bias

More with repeat MI DropoutsCrossover

Measurem

Specific ca


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Controlling Bias in Cohort

Random selection

Randomly select patients or randomly assign them to groups

Restriction

Limit the range of patient characteristics i.e. age group,residence etc.

Matching

For each patient in one group select one or more patients witthe same characteristics (except for the factor under study) tothe other group


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Controlling Bias in Cohort

Stratification

Compare rates within subgroups

Simple adjustment

Adjust crude rate by assigning weight for one or fewcharacteristics

Multivariate

Adjust for difference in multiple factors using statisticalmodeling techniques

Sensitivity analysis

Best case/worst case


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In the end

Biased?

Perhaps. Does it matter?

Do you have better data?


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Survival Curve Analysis


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A 43 year old male with dyspnea consulted at PGH. Hewas initially diagnosed to have PTB and treated as suchwith no relief. He came to the ER in respiratory distress.Chest x-ray showed pulmonary mass with extrathoracicextension.

Impression: Bronchogenic carcinoma, T4, N3 with bonemetastasis highly considered

The patients wife asked Doctor, will my husband be ableto go home?

The Patient


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EBM practitioner

Among patients who have bronchogenic cancer who

have extensive involvement, nodal metastasis and

probable bone metastasis, what is the probability ofsurvival at 5 years?

The physician-in-charge

Until when will the physician strive for the utmost

welfare of a patient succumbing to his terminal illness?

The Clinical Question


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MEDLINE search

bronchogenic carcinoma

prognostic factors (extensive involvement,

nodal or bone metastasis)

5 year survival

The EBM Practitioner


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Lassen et al.

Long-term survival in lung cancer: Post-treatmentcharacteristics in patients surviving 5 to 18 years -

An analysis of 1,714 consecutive patients

Journal of Clinical Oncology, 1995; 13: 1215-1220.

The Article


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Was there a well defined sample of patients at a similarpoint in the course of the disease.

YES 1,714 consecutive patients who wereadmitted in a hospital for treatment andincluded in clinical trials were included. Allpatients underwent pre-treatment stagingprocedures.

Are the Results Valid


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Was follow-up sufficiently long and complete?

YES Follow-up was done for 5 years or more.



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Were objective and unbiased outcome criteria used?

YES Main outcome was survival or mortality.Outcome is measured as alive or dead.



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Was there adjustment for important prognostic factors?

YES Logistic regression analysis, adjustmentwas done for other prognostic factor.



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How large is the likelihood of the outcome event in a specified period of

time?

For extensive stage, bone metastasis is a significant prognostic factor

survival rate with bone metastasis = 2.2%

survival rate without bone metastasis = 4.5%

survival with chest irradiation = 3.2%

survival rate with no chest irradiation = 3.6%

presence of metastasis decreases probability of survival by 50%

What are the Results


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How precise are the estimates of the likelihood?

P value = 0.01 for bone metastasis

What are the Results


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Were the study patients similar to my own?

YES Subjects included in this study were patients

admitted to a hospital for treatment.

Will the Results Help Me

in Caring for My Patient


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Will the results lead directly to selecting or avoiding therapy?

YES Radiation treatment can be avoided.




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Are results useful for reassuring or counseling patients?

YES With extensive lesion and presence of metastasis

probability of survival is low. Radiation therapy is nothelpful.




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The clinical question

Among patients who have bronchogenic cancer who haveextensive involvement, nodal metastasis and probablebone metastasis, what is the probability of survival at 5years?

The EBM practitioners answer

The probability of the patient surviving in 5 years is verylow (2.2%). Radiation therapy does not offer anyadvantage. The money to be spent for radiationtreatment can be used for other purpose.

The EBM Practitioner


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The question of the physician-in-charge

Until when will the physician strive for the

utmost welfare of a patient succumbing to his

terminal illness?

The answer

Until the patient holds on to life.

The Decision in the Old Paradigm


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The patient was admitted to the wards for antibiotictreatment (clindamycin) for the pneumonia

Radiation therapy was done

On the 27th hospital day culture of tracheal aspiraterevealed Pseudomonas infection and antibiotic was shifted

to imipenem. Five days later the patient went home against medical

advice

THE FAMILY HAD NO MORE FUNDS TO SUSTAIN

TREATMENT !

The Rest of the Story


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Bronchogenic carcinoma, T4, N3 with bone metastasis

highly considered

P 100,000.00 Palliation

P 100,000.00 Start a sari-sari store

Two year computer scienceSend three overseas worker

What is the Price of a Life


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Keep on Asking

Keep on Searching

Keep on Learning

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4 - EBM Prognosis