Risk Factors of Lippert et al for Recurrence After a First Spontaneous Pneumothorax

 

General parameters:

(1) age

(2) height to weight ratio (see page 325)

(3) pulmonary fibrosis seen on chest X-ray (I could not find this discussed in the text, only in the footnote to Table 1 on page 326)

 

height to weight ratio in females =

= ((height in cm) / (body weight in kg))

 

height to weight ratio in males =

= ((height in cm) / (body weight in kg)) + 0.22

Parameter	Finding	Points
age of the patient	< 60 years	0
	>= 60 years	1
height to weight ratio	< 3.2	0
	>= 3.2	1
pulmonary fibrosis	absent	0
	present	1

 

number of risk factors =

= SUM(number of parameters present)

 

Number of Risk Factors	Percent Recurrence Free at 3 Years	Percent Recurrence Free at 10 Years
0	86%	83%
1	77%	53%
2	43%	< 43%
3	0%	0%

from Figure 3, page 328

 

For a patient without pre-existing lung disease, then being a nonsmoker is associated with an increased risk of recurrence.

 

prognostic index if no pre-existing lung disease =

= (2.28 * (points for pulmonary fibrosis)) + (1.57 * (points for age)) + (1.11 * (points for height-weight ratio)) + (0.82 if never smoked)

 

Interpretation:

• minimum prognostic index: 0

• maximum prognostic index: based on formula I get 5.78, according to Table 4 it is 7.15. This could be a typo; with a mean 3.48 +/- 0.84 the mean + 2SD would be 5.16.

• The text now gets to be a bit ambiguous. It states that 7 equidistant intervals were created, with the 4th, 5th, 6th and 7th intervals combined into 1 due to a small number of patients. The actual break points were not listed (at least I could not find them).

• If the highest value is 5.78, then the intervals would be 0 to 0.83 (includes nonsmoking), 0.831 to 1.66, 1.661 to 2.49, and > 2.49. This is what I will use in the implementation.

• If the highest value is 7, then the intervals would be 0 to 1 (includes nonsmoking), 1 to 2, 2 to 3, and > 3.

 

Prognostic Index Group	Percent Recurrence Free at 5 Years	Percent Recurrence Free at 10 Years
1	98%	98%
2	74%	69%
3	54%	40%
4	47%	31%

from Figure 4 page 329

 

where:

• Patients with Marfan's syndrome have a risk for spontaneous pneumothorax. The risk associated with the increased height to weight ratio may be associated with these patients.

• Pulmonary fibrosis is listed as a risk factor for patient without pre-existing lung disease in Table 4. Pre-existing lung disease was defined as COPD or asthma.

• A person who has had more than 1 episode of spontaneous pneumothorax would seem to be at higher risk for further episodes.

• Interestingly pulmonary blebs and bullae were only present in 5% of the patients with no pre-existing lung disease and 15% of those with pre-existing lung disease (see Table 1).