Gender differences in cystic fibrosis: Pseudomonas aeruginosa infection

08954356(94)00230-4

Pergamon

J Clin Epidemiol Vol. 48. No. 8, pp. 1041-1049. 1995 Copyright 0 1995 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0895-4356195 $9.50 + 0.00

GENDER DIFFERENCES IN CYSTIC FIBROSIS: PSEUDOMONAS AERUGINOSA INFECTION CATHERINE

A. DEMKO,*

PAMELA J. BYARD and PAMELA B. DAVIS

Department of Pediatrics, Case Western Reserve University, 2101 Adelbert Road, Rainbow Babies and Children’s Hospital, Cleveland, OH 44106, U.S.A. (Received in revised form

16 November 1994)

median survival age for females with cystic fibrosis (CF) is approximately 3 years younger than for males. We tested whether earlier acquisition of Pseudomonas aeruginosa (PA) by female CF patients or the greater impact of this organism on their lung disease,or both, contribute to their poorer survival. PA infection status, survival, pulmonary function tests, and chest X-ray scores from patients who were followed at our center for at least 2 years with a minimum of three respiratory cultures per year were analyzed (n = 848). The median age of chronic infection with mucoid PA was 1.7 years earlier in females than in males. Patients infected with mucoid PA had poorer survival, chest X-ray scores,and pulmonary function tests than patients who had either no Pseudomonas speciesor only the nonmucoid phenotype. Acquisition of mucoid PA was associated with an accelerated rate of decline in pulmonary function. However, the rate of change of pulmonary function after mucoid PA infection was similar for males and females. Moreover, even among patients who had only the mucoid form or only the nonmucoid form, males had better percent predicted forced expiratory volume in 1 set and better survival. Therefore, factors in addition to earlier acquisition of mucoid PA may contribute to the poorer survival of female CF patients.

Abstract-The

Cystic fibrosis

Pseudomonas

Gender differences

aeruginosa

INTRODUCTION

Female patients with cystic fibrosis (CF) have a significantly poorer prognosis and lower survival rates than same-age male counterparts. The median survival age for females is 3 years less than for males [l]. The gender gap in survival is evident well before puberty and persists throughout life, and is thus difficult to attribute to pubertal hormonal influences. In addition, girls at our CF center have more normal growth and higher height and weight percentiles than boys [2,3], so poor nutritional status does not account for the females’ poorer survival. *Author

for correspondence.

The major cause of morbidity and mortality in CF is the lung disease, and a striking feature of CF lung disease is the high propensity for chronic bacterial infection of the lower airways, particularly with Pseudomonas aeruginosa (PA). Once this organism is consistently recovered from lower respiratory secretions of CF patients, it is seldom eradicated by host defense mechanisms or antimicrobial therapy [4]. The excessive PA strains eventually produce amounts of extracellular polysaccharide alginate, giving rise to the mucoid phenotype typically associated with CF [5]. The presence of the mucoid variant in the lung has been associated with increased humoral response [6,7], poorer clinical state [8, 91, and poorer survival [lo, 111, relative to uninfected patients.

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Catherine

A. Demkoet al.

In order to determine whether differences in the acquisition of PA, and particularly the mucoid phenotype, contribute to the gender gap in survival in CF, we undertook a retrospective analysis of 848 patients seen in the Cleveland CF Center. We investigated whether female patients acquire PA or its mucoid variant at an earlier age than males, or whether its chronic presencein the lung has a more severeeffect on the clinical course of female patients. Either result may contribute to poorer pulmonary function at an earlier age in female patients and to their poorer survival. METHODS Patient data CF was diagnosed by a sweat chloride value of at least 60 mEq/l and either typical CF pulmonary or digestive symptoms, positive family history, or two known cystic fibrosis transmembrane conductance regulator (CFTR) mutations. There is no significant difference in the mean age of diagnosis for males and females (2.5 years for males vs 2.9 years for females, p = 0.26). Of the 554 patients tested for CFTR mutations, no gender differences in genotype frequencies have been found. Sputum samples or deep throat swabs taken after coughing from nonexpectorating patients were obtained at outpatient clinic visits and during hospital stays and processedby standard clinical laboratory methods for the isolation and identification of PA [12]. The usefulness of sputum [13] and throat swabs [14,15] as predictive measuresof lower respiratory bacteria have been reported. Morphological distinction between mucoid and nonmucoid strains was made as described previously [ 161.The respiratory culture results were entered into the relational computer database at the Cleveland CF Center, which also contains demographic information and longitudinal chest X-ray clinical scores and pulmonary function tests (PFTs). Chest X-ray scores were assigned based on a modification of the Shwachman scoring system with a maximum of 25 points for normal appearing lungs [17, 181.The percent predicted forced expiratory volume in 1 set (FEV, ) for age and gender was used for analysis of pulmonary function. PFTs were performed through 1986 on a water-sealed spirometer (Warren E. Collins, Braintree, MA) automated using a Digital Equipment Corporation PDP-8/E computer. After 1986, tests were done on a Medical

Graphics CAD/Net Pulmonary Function System (Model 1070-85).Careful testing at the time of transition between these two systemsshowed comparability of measurements between them. All tests were performed on equipment which met the current American Thoracic Society (ATS) standards and tests were selected for recording based on ATS criteria [19]. Age of PA infection For this analysis, patients were selected who were actively followed at our center for at least 2 years, with a minimum of three respiratory cultures per year. Cultures were obtained between 1954 and 1990. According to these criteria, 848 patients (443 males and 405 females) had sufficient data to determine whether they (1) arrived with PA, (2) became infected with PA while under our care, or (3) left our center without PA infection. While the age of PA infection can be determined directly for patients in group 2, group 1 data are considered left censored and group 3 data are right censored. Although the age of infection for patients with censored data cannot be determined directly, these patients do provide some information. For patients with left censored data, the age at which they arrive at our center with PA provides an upper limit on the age of infection, while data from patients who leave without becoming infected provide lower limits. Estimates of median infection agesfor events which occur at an early age will tend to be inflated if based only upon group 2 patients because the data for patients with the youngest ages of infection will tend to be left censored. Conversely, ages for events which occur at later ages will tend to be underestimated if they are based solely on patients with uncensored data because there will be a higher proportion of right censoring for such events. Using a survival analysis program that handles both left and right censored data [20], we estimated the median age of four different stagesin the progression of PA infection in CF patients: the first age of (1) any positive PA culture, (2) any chronic PA infection, (3) a positive mucoid PA culture and (4) chronic mucoid PA infection. For the first two events, the age may be associated with either nonmucoid or mucoid PA, whichever phenotype is detected first or becomes chronic first. For the last two events, only ages associated with the mucoid phenotype are included. Patients were classified as chronically infected with PA when

GenderDifferencesin Cystic Fibrosis

at least 50% of their cultures in a 12 month period were positive. The SAS LIFEREG procedure fits parametric models to the log transformed age of PA acquisition data. In this case, a Weibull distribution was fitted to the data by maximum likelihood using a ridge-stabilized NewtonRaphson algorithm, with gender included as a categorical independent variable. Differences in the cumulative density function of PA acquisition according to age in male and female patients were tested for statistical significance by x2 tests. For analysis of only nonmucoid PA, data from a subsample of the original 848 patients was analyzed. This subset (n = 569) excludes patients who either presented at our center with a mucoid strain, or were observed to become infected with both mucoid and nonmucoid strains at the same time and therefore provide no information about the age of infection with nonmucoid PA alone. The LIFEREG procedure was fitted to this new subsample of patients to estimate the median age of (1) an initial positive nonmucoid PA culture and (2) chronic nonmucoid PA infection. Impact of PA infection on CF lung disease Earlier acquisition of PA would not contribute to the gender gap in survival unless it had a negative impact on the clinical course of the CF lung disease. Therefore, the effect of PA infection on 10 year survival and on two measuresof pulmonary involvement in CF, chest X-ray scoresand pulmonary function, was assessed.In addition, the responses of males and females were compared in order to test whether acquisition of PA had a more severe impact in females. Statistical tests for clinical outcome measures were conducted with the SPSS/PC statistical package, with a Type 1 error rate of 5%. Survival analysis All patients for whom PA infection status could be determined at 6 years of age were included in the IO-year survival analysis. The 491 patients who met these criteria were divided into those who became infected with mucoid PA by the age of 6 years (n = 130) and those with no chronic mucoid PA infection by the age of 6 years (n = 361). Survival in these groups over the next 10 years was compared using Kaplan-Meier cumulative survival function analysis. Group differences were tested

1043

for statistical significance using the log rank test. Chest X-ray scores Cross-sectional data from 505 patients who had at least one chest X-ray at our center before 6 years of age are included in this part of the analysis. This cross-sectional approach assesses the effect of PA infection on lung diseasein very young patients, before the age at which PFTs become available. Active patients generally have at least two chest X-rays per year. The best yearly score for each patient at ages I-6 years was used in the analysis. Scoresat each age were grouped by PA infection status (chronic mucoid PA, chronic nonmucoid PA, no chronic PA) and an analysis of covariance was performed using gender and PA status at the time of the X-ray as main effects and age, age*, and age3as covariates. Special contrasts were specified to compare means for the nonmucoid and no PA groups and then to contrast the means for these two groups with the mean for the mucoid PA group [2 11. PFTs Active patients over the age of 5 years generally have at least two PFTs per year. To compare lung function among patients with chronic mucoid PA, chronic nonmucoid PA, and no chronic PA, a cross-sectional analysis of the best yearly measurement of percent predicted FEV, for ages&16 years was performed. The analysis is based on data from 713 patients who had at least one PFT at our center in this age range. An analysis of covariance was conducted according to gender and PA status, with age, age*,and age3 as covariates. Becausethe mucoid variant of PA might be present in vivo for a time before it can be detected by culture in vitro, measurementson patients within 1 year prior to the date of chronic mucoid PA infection were deleted from the no PA and nonmucoid PA groups. In order to determine more directly the impact of chronic mucoid PA on lung function, the percent predicted FEV, obtained from 198 patients both before and after mucoid PA infection were analyzed longitudinally. This subsample includes only patients with at least two PFTs before and two PFTs after mucoid PA infection. Linear regressions of FEV, on time were conducted for each patient to calculate a slope and an intercept for the time period l-3 years prior to mucoid PA infection and a separate slope and intercept for the time period O-3

Catherine A. Demko et al.

1044

for initial mucoid and p = 0.078 for chronic mucoid PA, based on x2 with 2 df ). The median age for each stage derived from only the uncensored data is compared with the median estimated by the LIFEREG program from the full data set in Table 1. The greatest discrepancy between the two sets of medians is for the age of initial PA culture, where over half of the casesin both males and females are left censored, resulting in a 4 year overestimate of the median when only uncensored cases are used. Compared to medians estimated from all cases,medians based only on uncensored cases tend to underestimate gender differences for all events except the initial PA culture. For chronic mucoid PA, the difference between male and female medians is only 0.9 years based on uncensored cases,compared to 1.7 years when all cases are used. There is no significant difference in the probability distributions of males and females for the age of initial positive culture for any PA phenotype (p = 0.586) but there are significant gender differences in the age distributions for initial recovery of mucoid PA (p = 0.021), chronic infection with any PA phenotype (p = 0.019), and chronic infection with mucoid PA (p = 0.002). When this analysis was restricted to the 569 patients with only nonmucoid PA, no significant effect of gender on the probability distribution of age of initial recovery (p = 0.825) or chronic infection (p = 0.094) with nonmucoid PA was detected.

years post-mucoid PA infection. The two intercepts represent the value of percent predicted FEV, at the time of mucoid PA infection (time 0), estimated by the pre- vs post-infection data. The first year of mucoid PA infection (i.e. the first year in which more than half the cultures were positive for mucoid PA) is designated the zero year. The time between the - 1 and zero year is not included in the regression equations because it is possible that the mucoid variant was present in viva during this time period, but not yet detected in culture. Therefore, this year may not reflect a true “before” infection period. To avoid overrepresentation of PFTs from hospitalized patients, the best test for each 1 month period was selected from patients with multiple measurements within a 1 month period. A mixed model analysis of variance was performed on the individual slopes and intercepts, with time period (before vs after mucoid PA infection) as a within subjects repeated measure factor and gender as a between subjects factor. Age of mucoid PA infection is included as a covariate in this analysis to control for the confounding of gender and age of infection. RESULTS

Age of PA infection The percent of male and female patients with left, right, and uncensored data for each of the four stages of PA infection are shown in Table 1. As expected, the number of left censored cases is highest for the age of initial PA culture, while the number of right censored cases is highest for the age of chronic mucoid PA infection. Although females have slightly higher proportions of left censored data and lower proportions of right censored data, the differences are not statistically significant for any of the events (p = 0.652 for any PA initial culture, p = 0.070 for chronic any PA, p = 0.166

Survival Of the 130 patients who acquired chronic mucoid PA before 6 years of age, 34, or 26.2%, died over the next 10 years. Among patients who acquired mucoid PA after age 6, 21 of 361 patients (5.8%) died. Cumulative survival curves are presented in Fig. 1. The difference in lo-year survival between the “early” and “late”

Table 1. Percent of censored and uncensored cases, and median ages of PA infection based on uncensored cases vs all cases Percent of cases Left censored

Any PA Initial Chronic Mucoid PA Initial Chronic

Uncensored

Median age in years Right censored

Uncensored cases

All cases

M

F

M

F

M

F

M

54 32

57 39

41 51

38 48

5 17

5 13

5.8 8.3

5.1 7.8

1.6 6.5

1.4 5.4

21 18

25 22

62 56

62 58

17 26

::

8.3 10.4

7.9 9.5

8.4 11.2

7.4 9.5

M = males, n = 443; F = females, n = 405.

F

M

F

1045

Gender Differences in Cystic Fibrosis

r

‘;;

0.90

.2 z 2

0.85

$ 3 6 ; E :

0.80 ‘-I--

Early

0.75

I 7.

0.70

Acquisiton

(4

Y=)

I,

----

Males Females

7

8

L L-

L

6

9

10

11

12

13

" 6

5

Fig. 2. Means and standard errors for X-ray score by age in patients with no PA (A), nonmucoid PA (a), and mucoid PA (0) from 2 to 6 years of age. Patients with mucoid PA differ significantly (p = 0.001) from the other groups.

L.--.-T

0.60

" 4

Age in Years I..-

0.65

I. 3

2

! iIL..-;

14

15

16

Age in Years

with mucoid PA before 2 years of age and thus comparisons are not shown before that age. Both PA status and the age covariates have significant effects on X-ray score (p < O.OOOS), whereas gender and the interaction of gender with PA status do not (p = 0.275 and 0.618). Although statistically significant, the difference between patients with nonmucoid PA and those with no PA is very small (age adjusted means are 19.9 and 19.0 vs 14.9 for mucoid PA). Thus, even at very young ages, the presence of mucoid PA is associated with more severe lung disease as shown by chest X-ray scores.

Fig. 1. Cumulative survival for males and females according to age of mucoid PA acquisition. Those who acquired mucoid PA before age 6 years had significantly poorer survival than those who acquired the mucoid phenotype later (p < 0.0005). However, with both groups, females had poorer survival (p = 0.010).

acquisition groups is highly statistically significant (p < 0.0005). Although mucoid PA infection has a major effect on survival, gender differences within PA groups are also statistically significant (p = 0.012), i.e. among patients who acquire mucoid PA before 6 years of age, females have higher mortality than males in the 10 year follow-up period.

PFTs Figure 3 shows the mean percent predicted FEV, by yearly age according to gender and chronic PA infection status based on crosssectional analysis of data between the ages of 6

Chest X-ray scores Cross-sectional mean scores according to PA status from 2 to 6 years of age are presented in Fig. 2. Only one patient was chronically infected

Nonmucoid

No PA

PA

Mucoid

85 .

I‘

.

PA

* . .

I

0 Males 0 Females

.

;%

5oL-----l 6

8

10

12

14

16

6

6

10

12

14

16

6

8

10

12

14

16

Age in Years Fig. 3. Mean percent predicted FEV, for male (open symbols) and female (closed symbols) patients at ages 6-16 years of age. Mean FEV, values are worse in patients infected with mucoid PA than in patients with either only nonmucoid PA or no PA at all (p < 0.0005). CE w&--E

1046

Catherine A. Demko ef al.

significantly lower than those for males (p = 0.027). However, the interaction term (pre vs post x gender) is not significant (p = 0.480). DISCUSSION

1

. -3

. -2

I -1

0

1

3

2

Years Since Chronic Mucoid PA Acquisition Fig. 4. FEV, in male (open symbols) and female (closed symbols) according to the number of years since chronic mucoid PA acquisition. Values are derived from the mean of individual slopes and intercepts calculated for 198 individual patients before and after the date of chronic mucoid PA acquisition. Statistical analysis is summarized in the table.

and 16 years. Analysis of covariance for FEV, revealed that the main effects for gender and PA status were both highly significant (p < 0.0005), but there were no significant differences in the age-adjusted means between the groups colonized by nonmucoid PA or by no PA (p = 0.520). Patients with chronic mucoid PA, however, had significantly lower age-adjusted FEV, values than the other two groups (p < 0.0005). There were no significant interaction terms for gender by PA status or for age by gender or age by PA status, suggesting that the decline in FEV, is similar for males and females with the same PA status. Results of the longitudinal analysis of FEV, are illustrated in Fig. 4. The mean rate of decline in pulmonary function as measured by the slope for FEV,, shown in Table 2, is significantly greater after infection with mucoid PA than before infection (p < 0.0005). The main effect for gender, however, is not statistically significant (p = 0.399). Thus, the decline in pulmonary function is more rapid after mucoid PA infection, but the decline for females is no more rapid than the decline for males. The intercepts estimated for the post-infection data are significantly lower than those based on the pre-infection data (p = 0.018), and those for females are

Either earlier acquisition of an organism with a deleterious effect on the clinical course, or a more severeimpact of that organism in females, or both might account for the gender gap in survival in CF. Our analysis of respiratory culture data from 848 CF patients reveals that the median age of the initial positive mucoid PA culture is 7.4 years for females, compared to 8.4 years for males. The median age of chronic mucoid PA infection is 9.5 years for femalesand 11.2 years for males. This age difference of 1.7 years is statistically significant, but does not account entirely for the 3 year difference in median age in survival according to gender. Very few studies have attempted to report median ages of PA infection for CF patients, and none have reported gender differences. Pedersen et al. [l l] reported a median age of infection of approx. 10 years for Danish patients. Presumably, this is based on patients with uncensored data for chronic infection with any PA phenotype. This median is slightly higher than the 8.3 years for males and 7.8 for females who have uncensored data at our center, and is a considerable overestimate when compared to our medians based on all cases(6.5 and 5.4 years for males and females). Kerem et al. [22] report mean ages of PA acquisition (presumably for the initial positive culture with any PA) of 7.18 f 5.19 years for CF patients born without meconium ileus and 4.29 -I 4.67 years for patients born with meconium ileus. It is not clear if thesemeans are based on the entire sample (n = 1017 without meconium ileus and 158 with meconium ileus) or on uncensored cases only, but they are much higher than the medians based on all cases at our center (1.6 years for males and 1.4 years for females). Interestingly, when our data are analyzed using mean ages for uncensored cases, patients with meconium ileus (n = 58, mean age = 4.9 + 5.8

Table 2. Regression analysis of % predicted FEV, before and after chronic mucoid PA infection (mean slopes and intercepts + SEM) Intercepts

Slopes

Males (n = 105) Females (n = 95) *Differs

significantly

Pre

Post

Pre

Post

+1.3*0.9 +0.2 f 1.1

-2.4 f 0.8* -2.5 * 0.9’

69.2 k 2.7 61.9 + 3.2

63.5 f 2.2* 58.8 f 2.3

from pre-infection

value (p -Z 0.05).

Gender Differences in Cystic Fibrosis

years) appear to acquire PA significantly sooner than those without meconium ileus (n = 354, mean age = 6.8 + 6.2 years, p = 0.030). When the data are analyzed using survival analysis on all 848 cases, however, the difference in probability functions is not significant (p = 0.052) and the medians are much closer (1.6 years for 739 patients without meconium ileus vs 1.l years for 109patients with meconium ileus). The gender differences reported above remain when meconium ileus is included as a second factor in the LIFEREG analysis of PA infection. The present study demonstrates that IO-year survival was influenced by early infection with mucoid PA as well as by gender (74% survival for early infection vs 94% for late). Several groups have investigated survival in patients stratified by PA status or age of PA acquisition. Kerem et al. [23] reported a IO-year survival greater than 78% in patients infected with PA regardless of age of PA acquisition. Their study did not distinguish between patients colonized with mucoid vs nonmucoid variants, and only 58% of the patients included in the analysis were reported to be chronically colonized. It is possible that including patients with intermittent or uncertain PA status as well as not distinguishing among patients with different PA phenotypes could obscure the effect of chronic mucoid PA. Henry et al. [8] reported a difference in 8-year survival between patients with mucoid compared to patients with nonmucoid or no PA (58% vs 89 and 92%, respectively). Our results consistently indicate that chronic mucoid PA infection is associated with greater severity for the indices of pulmonary disease examined, X-ray scores and percent predicted FEV,. In patients under the age of 6 years, mean X-ray scores from those with mucoid PA were significantly lower than from patients without mucoid PA, regardless of gender. Similarly, after 6 years of age, when patients could perform pulmonary function tests, mean FEV, values from patients with mucoid PA were significantly worse than those from patients without mucoid PA. Further evidence for the impact of mucoid PA in the lungs of these patients was obtained by longitudinal analysis of pulmonary function before and after acquisition of mucoid PA. The rate of decline of pulmonary function accelerated markedly after acquisition of chronic mucoid PA, although the rate of decline in FEV, was similar in males and females. All of these data

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are consistent with the hypothesis that the acquisition of the mucoid variant of PA is associated with poorer prognosis. This result is in agreement with Pedersen et al. [ll], who found that patients with mucoid PA had poorer FEV, and weight for height than those colonized by nonmucoid strains or those with no PA at all. Deleterious effects were less consistent for nonmucoid PA. Only for X-ray scores in younger patients was there a significant difference between patients with nonmucoid PA and those with no PA. The hypothesis that nonmucoid PA affects survival could not be tested in our lo-year follow-up study, because most patients who acquire nonmucoid PA before the age of 6 are likely to also acquire the mucoid phenotype within the follow-up period. Although the presence of the nonmucoid phenotype may not have severeconsequencesby itself, the usual progression of PA infection appears to involve the conversion of the nonmucoid to its mucoid counterpart [2426]. The reasons for conversion to the mucoid phenotype are not clear. Alginate synthesis is under the control of a complex network of regulatory and structural genes,present in both nonmucoid and mucoid phenotypes. In vitro, environmental conditions such as dehydration [27] and abnormal salt concentrations [28] have been reported to affect the transcriptional activity of alginate genes.Additionally, growth of nonmucoid variants under conditions of nutrient deprivation or in the presence of lung surfactant results in the emergence of the mucoid phenotype [29]. The CF airway liquid may be relatively dehydrated and have abnormal salt composition becauseof the altered ion transport associated with the basic defect, providing a suitable environment for the emergence of the mucoid phenotype. These studies would support the hypothesis that the nonmucoid variant converts to the mucoid phenotype in vivo, but the influence of these abnormalities on the phenotypic expression of mucoid PA in vivo has not been assessed directly. Further, it is unclear why there should be a gender difference in the propensity to develop mucoid PA unless one or more of these environmental stresses exists differentially in males and females. The possibility exists that some patients acquire the mucoid phenotype through crossinfection rather than conversion of their infecting strain. Several studies of phenotypic and/or genome probe typing methods demonstrate that

1048

Catherine A. Demko et al.

multiple coinfecting PA phenotypes in CF patients are often the same strain, although heterogeneity among strains does exist, especially during transient colonization [30-321. Because only 6% of our patients have had the mucoid phenotype as an initial colonizing strain, it seems unlikely that cross-infection contributes significantly to the rate of infection with the mucoid phenotype. A prospective study using a combination of typing methods to identify newly isolated mucoid PA from nonmucoid PA infected patients would be necessary to answer this question. Our results suggest that female CF patients become infected with mucoid PA earlier than males, and that mucoid PA has significant detrimental effects on the progression of CF lung disease. However, we do not find significant evidence that mucoid PA infection has a more severe effect on female X-ray scores in early childhood, on female pulmonary function at age 616 years, or on female pulmonary function up to 3 years after the onset of PA infection. Thus, it appears that the gender gap in survival in CF may be explained in part by earlier acquisition of a more noxious form of bacteria by females, but not by greater impact of this organism on their lung disease, at least within the follow-up periods possible for our mixed longitudinal sample. Even when the patients are separated by colonization status, the percent predicted FEV, is worse for females at any given age than for males, suggesting that other, unknown factors may contribute to gender differences in the progression of CF lung disease. We conclude that earlier infection with mucoid PA by female patients with CF is associated with poorer pulmonary status and poorer survival, relative to males. These findings suggest that research to provide therapy aimed at eradicating PA at initial colonization before it has a chance to convert to the mucoid phenotype, or therapy aimed specifically at eliminating the alginate material in patients already infected with the mucoid phenotype remain important avenues to pursue in efforts to decrease morbidity and improve survival in patients with CF. Acknowledgemenrs-This work was supported by grants from the National Institute of Diabetes, Digestive and Kidney Diseases P30 DK27651 and HD-23805. We are grateful to the physicians of the CF Center at Rainbow Babies and Childrens Hospital and to the pulmonary function and microbiology technicians who through the years have contributed to the CF patient database

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