Physical development and pulmonary function in children and adolescents treated at two cystic fibrosis treatment centres in Poland

Introduction
Cystic fibrosis is diagnosed in about one in every 2,500 live births in Poland [1]. The disease is caused by a mutation in the cystic fibrosis trans-membrane conductance regulator (CFTR) gene, which is located on chromosome 7. More than one thousand different mutations of this gene have been found [2]. The most common mutation is D508, which is present in almost 70% of the cases reported [3]. Patients who are homozygous for this mutation generally have a more severe form of the disease characterized by greater impairment of pulmonary function and a shorter life expectancy [4, 5].
Delayed physical development, delayed puberty and malnutrition are common in children suffering from cystic fibrosis, and are important prognostic markers of the course of the disease and the life expectancy of the patient. In a study on patients with cystic fibrosis in the United States, the probability of death was at least three times higher in patients in the lowest fifth percentile with respect to body weight than in the tallest patients [6]. In another study, there was a strong positive correlation between weight deficit and the probability of death. Regardless of the state of the respiratory system, malnutrition is an essential prognostic marker of the course of the disease and the life expectancy of the patient [7].
Malnutrition in patients with cystic fibrosis has a complex aetiology that can be described as a vicious cycle. Children with cystic fibrosis require 30 to 50% more calories per day than their healthy peers [8, 9].
Respiratory dysfunction is the main factor that determines the quality and length of life in patients with cystic fibrosis [10-12]. More than 95% of deaths in these patients are caused by chronic purulent obturative lung disease [13].
In functional studies of the respiratory system, the degree of airway obstruction can be estimated by measuring the predicted forced expiratory volume in one second (FEV1). In patients with cystic fibrosis, predicted FEV1 depends on several factors, including age, sex and body height. Previous studies also indicate that predicted FEV1 may also be affected by nutritional status, the type of CFTR gene mutation, and the presence of respiratory tract infection caused by Pseudomonas aeruginosa
[4, 14-16].
The aim of this pilot study was to assess physical development and respiratory function in children and adolescents with cystic fibrosis treated at two cystic fibrosis treatment centres in Poland, and to determine whether pulmonary function in these patients was affected by nutritional status, the type of CFTR gene mutation and infection caused by P. aeruginosa.

Material and methods
A pilot study was carried out on twenty boys and thirteen girls treated for cystic fibrosis during the spring of 2006 at the Institute of Mother and Child in Warsaw and the Pulmonary Medicine and Allergy Centre in Karpacz, Poland. The mean age of the subjects was 14.0 ±6.7 years, with a minimum of 6.2 years, and a maximum of 18.5 years.
In all patients, the diagnosis was confirmed by positive sweat tests. The mean age of diagnosis was about 2.5 years, with a minimum of one month, and a maximum of twelve years.
The children in this study were treated in accordance with the guidelines published by the Polish Working Group for Cystic Fibrosis [17]. According to these guidelines, the quality of life and the longevity of patients with cystic fibrosis are to be improved by centralized medical care. The treatment protocol should include the following elements:
• individually tailored high calorie diets and pancreatic enzyme supplements, which are especially important when absorption in the gastro-intestinal tract is reduced; in the present study, all of the patients were on special diets. 88% had exocrine pancreatic insufficiency and were receiving pancreatic enzyme supplemen-tation;
• effective, timely and targeted antibiotic therapy, especially of respiratory infections; 18% of the patients were receiving antibiotic treatment to control pulmonary infection caused by P. aeru-ginosa; infection was diagnosed by sputum culture, and appropriate antibiotics were selected on the basis of sensitivity testing; among the antibiotics prescribed were Colomycin, tobra-mycin, azlocillin, ciprofloxacin, ceftazidime and colistin, either alone or in combination; antibiotics were administered orally, intravenously or by aerosol inhalation, depending on the nature of the drug;
• physical therapy to increase stamina, mobility, respiratory competence, and growth in muscle and bone growth; all of the patients were receiving appropriate physical therapy at the time of this study; and
• regular follow-up visits to monitor growth and respiratory parameters; the children in this study came for follow-up visits every three or 6 months.
Physical development and pulmonary function were evaluated by collecting anthropometric and spirometric data on admission and during follow-up visits. All of the subjects and their legal guardians consented to the study.
Anthropometric measurements were performed in accordance with the procedures described by Martin and Knusmann [18]. The following data were collected: body height, body weight, leg length, trunk length, chest depth and chest width. Height was measured with an anthropometer accurate to 1.0 mm. Weight was measured with a scale accurate to 0.1 kg. Chest measurements were made with bow calipers accurate to 1.0 mm.
The following ratios were also calculated: trunk length to body height, leg length to body height, and chest depth to chest width. The body mass index was also calculated.
Anthropometric measurements were recorded in terms of standard deviations away from the age-specific and sex-specific reference means for the general population of Poland as determined by a survey that is widely recognized as valid for research purposes [19]. Normality was analyzed using the Shapiro-Wilk test. Differences between the mean values for the patients and the reference group and between boys and girls were tested using Student’s t-test.
Nutritional status was assessed by calculating Cole’s nutritional status index (CNSI) in accordance with the following formula [20]:

CNSI = [ body weight × (standard body length)2 ] × 100
standard body weight × (body length)2

Nutritional status was recorded on the basis of the score as follows:
> 110: over-nutrition;
90-110: normal nutrition;
85-90: slight malnutrition;
75-85: moderate malnutrition; and
<75: severe malnutrition.
None of the subjects were diagnosed with other conditions that could affect nutritional status, such as CF diabetes or gastro-intestinal reflux.
Spirometric measurements were performed during routine check-up visits at three to six month intervals. Data recorded included forced vital capacity (FVC), forced expiratory volume in one second (FEV1) and forced expiratory flow (FEF25-75). All spirometric parameters were measured using an MES JAEGER 100 spirometer in accordance with the procedures recommended by the Polish Phthisio-pneumological Society [21]. All results were recorded as percentages of the predicted values, standardized for height and sex [22, 23].
Molecular DNA studies had been previously carried out on all patients in order to determine the type of CFTR gene mutation. The studies were carried out at the Medical Genetics Laboratory of the Institute for Mother and Child at the time the patients were admitted.
The effect of nutritional status on pulmonary function was determined using Pearson’s linear correlation. The effect of standardized body weight, CFTR gene mutation type, and infection caused by P. aeruginosa on the percent of predicted FEV1 was assessed using the multiple regression method. Results were considered statistically significant at p < 0.05. All calculations were carried out using the STATISTICA 7.0 software package.

Results
The results for the anthropometric measurements are presented in Table I. Mean body height was lower in the study group than in the reference population. Eighteen percent of the patients had severe developmental problems, and had body heights that were more than two standard deviations below the mean for the reference population.
Mean body weight and body mass index were also significantly lower in the study group than in the reference population. Over 60% of the patients were malnourished, and a third of these were severely malnourished. None of the patients were overweight (Figure 1).
Mean leg length was considerably lower in the study group than in the reference population, as was the ratio of leg length to body height. On the other hand, mean trunk length was higher than in the reference population, as was the ratio of trunk length to body height. Chest depth was higher and chest width was lower in the study group than in the reference population. The ratio of chest depth to chest width was therefore considerably higher than in the reference population.
There were no statistically significant differences between boys and girls in any of the anthro-pometric measures (data not shown).
The results for the spirometric measurements are presented in Table II. Percent of predicted FVC, percent of predicted FEV1, and percent of predicted FEF25-75 were lower in the study group than in the reference population. Percent of predicted FEV1 was highest in those patients who were normally nourished or only slightly malnourished, and lowest in those patients who were severely malnourished (Figure 2). There was a strong positive correlation between percent of predicted FEV1 and Cole’s nutritional status index (r2 = 0.49, p < 0.01).
In terms of the type of mutation identified, the patients could be divided into three groups. Fifty five percent of the patients were homozygous for the mutation D508. Twenty seven percent had D508 and another mutation such as R334W or R117H. Eighteen percent had mutations other than D508 such as 3849+10kbC®T/3849+10kbC®T or 3849+10kbC®T/3659delC.
The results of the multiple regression are presented in Table III. There was a strong positive correlation between standardized body weight and percent of predicted FEV1 (corrected R2 = 0.43). On the other hand, there was no clear correlation between the type of CFTR gene mutation or infection caused by P. aeruginosa and percent of predicted FEV1.

Discussion
The results of this study confirm the results of previous studies in Poland and elsewhere in which body height and body weight were lower in patients with cystic fibrosis than in the general population [11-13, 24-28].
Based on studies carried out in Denmark and Australia, physical development and nutritional status in patients with cystic fibrosis are significantly improved when the patients are treated in specialized cystic fibrosis treatment centres. In some cases, growth parameters can even approach the values reported for the general population [29, 30]. Proper assessment of physical development and nutritional status and effectively targeted treatment to correct developmental deficiencies are essential for mitigating the symptoms of cystic fibrosis and prolonging the lifespan of the patient.
The children in this study were treated in accordance with the guidelines published by the Polish Working Group for Cystic Fibrosis, according to which the treatment protocol should include individually tailored high calorie diets and pancreatic enzyme supplements [17]. Nevertheless, over sixty percent of the children in this study were malnourished, and a third of these were severely malnourished. This suggests that their parents failed to strictly adhere to the recommended guidelines.
Failure to adhere to the treatment plan is a major problem in children from families with a low socio-economic status. Children with cystic fibrosis from poorer families are more likely to be malnourished, and, as a result, are more likely to suffer from growth retardation, pulmonary insufficiency and reduced lifespan [31]. Malnutrition in these children may be due to the additional cost of providing a special diet, which may strain or exceed the financial resources of the family. On the other hand, it may also be due to the fact that the parents do not possess the knowledge and sophistication required to correctly and consistently implement the treatment plan, including the special diet.
In this pilot study, parental compliance to nutritional guidelines was not monitored, and the socio-economic status of the patients’ families was not taken into account. However, these factors will be included in the full-scale study that is currently underway.
The patients in this study had significantly different body proportions than the reference population. They were considerably shorter, mainly because they had much shorter legs than their healthy peers. In normal individuals, leg length increases rapidly during the adolescent growth spurt. In patients with cystic fibrosis, however, this process is delayed by about ten months, and the annual increase in height is about one centimetre less than in healthy adolescents [32, 33]. The children with cystic fibrosis had infantile body proportions. Their legs were short and their trunks were long in comparison to their height. Infantile body proportions have also been found in abused children and in children who have undergone premature puberty [34, 35]. In the subjects in this study, chest depth was relatively high compared to chest width. This had also been observed in a previous study on children with cystic fibrosis, in which abnormalities in chest structure persisted in spite of treatment [27].
In the patients in this study, predicted FEV1 was significantly lower than in the general population. This agrees well with the results of previous studies [14, 15, 36].
There was also a strong correlation between nutritional status and FEV1, which is also consistent with previous reports [13, 16, 24]. In one study on children with cystic fibrosis between three and 6 years old, nutritional status was strongly correlated with respiratory function. The authors concluded that adherence to proper nutritional practices from early childhood on can significantly improve respiratory function [24]. In another study, proper and timely nutritional intervention slowed down the loss of respiratory function as estimated on the basis of the percent of predicted FEV1 [13].
Preserving respiratory competence is a high priority in treating children with cystic fibrosis because impaired respiratory function can increase morbidity and mortality. In one study, the probability that a child with cystic fibrosis would survive the next two years fell to 50% if the percent of predicted FEV1 fell below 30% [37]. In another study, the annual rate at which the percent of predicted FEV1 declined was found to be a reliable prognostic indicator [36].
Over the past fifty years, considerable progress has been made in arresting the loss of respiratory function in children with cystic fibrosis. In one study, the annual rate at which the percent of predicted FEV1 declined was considerably lower in children born in the 1990s than in children born in the 1960s [15].
In the present study, there was no correlation between the type of CFTR gene mutation and FEV1. In previous studies, the rate at which respiratory function is lost was particularly high in patients who were homozygous or heterozygous for the mutation D508 [4, 5].
Furthermore, there was no correlation between infection caused by P. aeruginosa and FEV1. In other studies on children with cystic fibrosis, the annual rate at which the percent of predicted FEV1 declined was elevated in patients who had respiratory tract infections caused by P. aeruginosa [15, 16].
These inconsistencies may be due to the small sample size of the patients in this pilot study. A full-scale study is underway to determine the effect of the type of CFTR gene mutation and infection caused by P. aeruginosa on pulmonary function in children with cystic fibrosis treated at specialized care facilities in Poland.

Acknowledgments
The authors are deeply grateful to the children and their parents for their patient cooperation in this study, and to Dr. G. Gąszczyk, Dr. D. Sands and Dr. A. Pogorzelski for their kind assistance.

References
1. Bożkowa K, Siwińska-Gołębiowska H, Rutkowski J, Nowakowska A. Epidemiologia mukowiscydozy u dzieci w Polsce [Polish]. Ped Pol 1971; 46: 677-84.
2. Hubert D. Mucoviscidose. EMC-Medecine 2005; 2: 34-41.
3. Sinaasappel M, Stern M, Littlewood J, et al. Nutrition in patients with cystic fibrosis: a European Consensus. J Cyst Fibros 2002; 1: 51-75.
4. Corey M, Edwards L, Levison H, Knowles M. Longitudinal analysis of pulmonary function decline in patients with cystic fibrosis. J Pediatr 1997; 31: 809-14.
5. De Gracia J, Mata F, Alvarez A, et al. Genotype-phenotype correlation for pulmonary function in cystic fibrosis. Thorax 2005; 60: 558-63.
6. Beker L, Russek-Cohen E, Fink R. Stature as a prognostic factor in cystic fibrosis survival. J Am Diet Assoc 2001; 101: 438-42.
7. Sharma R, Floreab VG, Bolgerb AP, et al. Wasting as an independent predictor of mortality in patients with cystic fibrosis. Thorax 2001; 56: 746-50.
8. Pencharz P, Durie P. Pathogenesis of malnutrition in cystic fibrosis, and its treatment. Clin Nutr 2000; 19: 387-94.
9. Schöni M, Casaulta-Aebischer C. Nutrition and lung function in cystic fibrosis patients: review. Clin Nutr 2000; 19: 79-85.
10. Johannesson M, Gottlieb C, Hjelte L. Delayed puberty in girls with cystic fibrosis despite good clinical status. Pediatrics 1997; 99: 29-34.
11. Groeneweg M, Tan S, Boot A, Jongste J, Bouquet J, Sinaasappel M. Assessment of nutritional status in children with cystic fibrosis: conventional anthropometry and bioelectrical impedance analysis. A cross-sectional study in Dutch patients. J Cyst Fibros 2002; 1: 276-80.
12. Rubinowicz M, Piotrowski R, Nowobilski R. Charakterystyka wybranych parametrów antropometrycznych i klinicznych u dzieci chorych na mukowiscydozę [Polish]. Pneumonol Alergol Pol 2005; 73: 172-7.
13. Zemel B, Jawad A, Simmons S, Stallings V. Longitudinal relationship among growth, nutritional status, and pulmonary function in children with cystic fibrosis: analysis of the Cystic Fibrosis Foundation National CF Patient registry. J Pediatr 2000; 137: 374-80.
14. Davis P. The decline and fall of pulmonary function in cystic fibrosis: New models, new lessons. J Pediatr 1997; 131: 784-90.
15. Que C, Cullian P, Geddes D. Improving rate of decline of FEV1 in young adults with cystic fibrosis. Thorax 2006; 61: 155-7.
16. Steinkamp G, Wiederman B. Relationship between nutritional status and lung function in cystic fibrosis: cross sectional and longitudinal analyses from the German CF quality assurance (CFQA). Thorax 2002; 57: 596-601.
17. Bożkowa K. et al. Zasady rozpoznawania i leczenia mukowiscydozy [Polish]. Stand Med 2002; 2: 29-36.
18. Martin R, Knusmann R. Anthropologie. Handbuch der vergleichenden. Biologie des Menschen. Vol. 1. Gustav Fischer, Stuttgart, New York 1988.
19. Palczewska I, Niedźwiedzka Z. Wskaźniki rozwoju somatycznego dzieci i młodzieży warszawskiej [Polish]. Med W Rozwoj 2001; 5: 19-55.
20. Lai HC, Corey M, Simmons S, Kosorek M, Farrell F. Comparison of growth status of patients with cystic fibrosis between the United States and Canada. Am J Clin Nutr 1999; 69: 531-8.
21. Zalecenia Polskiego Towarzystwa Ftyzjopneumonologicznego dotyczące wykonywania badań spirometrycznych [Polish]. Pneumonol Alerg Pol 2004; 72: 6-32.
22. Willim G, et al. Wartości należne wskaźników oddechowych dzieci i młodzieży [Polish]. IGiChP Oddział w Rabce 1998; 1-62.
23. Tomalak W, Radliński J, Pogorzelski A, Doniec Z. Reference values for forced inspiratory flows in children aged 7-15 years. Pediatr Pulmon 2004, 38: 1-4.
24. Wagener JS, Johnson CA, Morgan WJ. Growth and nutritional indexes in early live predict pulmonary function in cystic fibrosis. J Paediatr 2003; 142: 624-30.
25. Walkowiak J. Stan odżywienia i rozwój fizyczny dzieci chorych na mukowiscydozę w świetle podstawowych wskaźników wagowo-wzrostowych [Polish]. Prz Ped 1998; 28: 208-12.
26. Szczepanik M, Krawczyński M, Cichy W, Walkowiak J. Rozwój fizyczny dzieci z mukowiscydozą z województwa wielkopolskiego [Polish]. Ped Prakt 2000; 8: 397-410.
27. Kosińska M, Szwed A, Cieślik J, Goździk J, Karbowy K. Assessment of the biological condition and nutritional status of adult patients with cystic fibrosis. Anth Rev 2005; 68: 53-64.
28. Umławska W, Susanne C. Growth and nutritional status in children and adolescents with cystic fibrosis. Ann Hum Biol 2008; 35: 145-53.
29. Nir M, Lang S, Johansen H, Koch C. Long term survival and nutritional data in patients with cystic fibrosis treated in a Danish centre. Thorax 1996; 51: 1023-7.
30. Collins C, MacDonald-Wicks L, Rowe S, O’Loughlin E, Henry R. Normal growth in cystic fibrosis associated with a specialized centre. Arch Dis Child 1999; 81: 241-6.
31. Schechter MS, Shelton BJ, Margolis PA, Fitzsimmons SC. The association of socioeconomic status with outcomes in cystic fibrosis patients in the United States. Am J Respir Crit Care Med 2001; 163: 1331-7.
32. Byard PJ. The adolescent growth spurt in children with cystic fibrosis. Ann Hum Biol 1994; 21: 229-40.
33. Haeusler G, Frisch H, Waldhor T, Gotz M. Perspectives of longitudinal growth in cystic fibrosis from birth to adult age. Eur J Ped 1994; 153: 158-63.
34. Wales JK, Herber SM, Taitz LS. Height and body proportions in child abuse. Arch Dis Child 1992; 67: 632-5.
35. Martinez SM, Preece MA, Grant DB. Body proportions in precocious puberty. Acta Paediatr Scand 1984; 73: 185-8.
36. Kerem E, Reisman J, Corey M, Canny GJ, Levison H. Prediction of mortality in patients with cystic fibrosis.
N Engl J Med 1992; 326: 1187-91.
37. Mill C, Warwick W. Risk of death in cystic fibrosis patients with severely compromised lung function. Chest 1998; 113: 230-4.