**2. Methods**

A longitudinal study on two representative samples consisting of CRF patients in predialysis. The first group followed a renal protection program, and the other conventional treatment (CT). SF-36 questionnaire was applied twice for both groups, with an interval of one year. The RPP actively searches for patients and interdisciplinary standardized professional care, whereas CT consists of patient-requested medical care and follows no protocol.

The eligible population consisted of 5884 people complying with the following criteria: a. Having health insurance with either of the two healthcare promoting institutions during 2007; b. Having a CRF diagnosis that complies with the criteria established in the 2007 KDOQI guidelines (NKF,2007); c. Being older than 16, and d. Having received no dialysis or renal transplants. Exclusion criteria: being registered with both healthcare providers during the follow-up year.

Study 36-Item Short Form (SF-36). The version used in this study was adapted for the

To follow the WHO's recommendation (Tazeen, 2006), the Colombian Ministry of Social Protection proposed a CRF prevention and control program for Colombian healthcare providers (Martínez & Valencia, 2005). One of such institutions has been developing a renal protection program (RPP) since 2004. Besides patient uptake and follow-up, this program also assists patients in the early stages of the condition to prevent progression and renal damage, to delay the need for renal replacement therapies (RRT). The Renal Protection Program (RPP) is an interdisciplinary healthcare program. It is based on a protocol that establishes educational talks and regular medical appointments for conducting clinical examinations and laboratory tests. The program is geared toward CKD patients and welcomes them since the early stages of their condition. Likewise, the program actively searches for early-stage CKD patients and refers them to nephrologists. The professionals involved in this program are: general practitioners, internists, nutritionists, nurses, and nephrologists. Their degree of involvement varies depending on the patients' CKD stage. First, a follow-up is performed on the underlying condition. Afterwards, patients in the first and second stages of CKD are assigned to the program's first healthcare level, which offers medical appointments with internists and nutrition professionals once per year for stage 1 patients, and every semester for stage 2 patients. The second healthcare level of the program is for patients in stages 3 and 4, and offers medical appointments with internists, nephrologists, and nutritionists every three years for stage 3 patients and every two months

In contrast, other Colombian healthcare providers offered conventional treatment (CT) in 2004. CT consists of providing healthcare through general medicine once the patients feel the need to request this service. Conventional treatment follows no healthcare guidelines, does not search for patients actively, and offers no laboratory tests or regular appointments. This study compares changes in the HRQOL of two patient groups during the early stages of CRF (one group having been exposed to a RPP from 2007 to 2008). Its aim is to provide evidence of interventions that ease the burden this disease represents for patients, families

A longitudinal study on two representative samples consisting of CRF patients in predialysis. The first group followed a renal protection program, and the other conventional treatment (CT). SF-36 questionnaire was applied twice for both groups, with an interval of one year. The RPP actively searches for patients and interdisciplinary standardized professional care, whereas CT consists of patient-requested medical care and follows no

The eligible population consisted of 5884 people complying with the following criteria: a. Having health insurance with either of the two healthcare promoting institutions during 2007; b. Having a CRF diagnosis that complies with the criteria established in the 2007 KDOQI guidelines (NKF,2007); c. Being older than 16, and d. Having received no dialysis or renal transplants. Exclusion criteria: being registered with both healthcare providers during

Colombian culture (Lugo et al., 2006).

for stage 4 patients.

and society.

**2. Methods** 

protocol.

the follow-up year.

A formula with repeated measurements proposed by Frison and Pocock in 1992 (Frison et al., 1992) was used to calculate the sample probabilistically. The criteria were: type 1 error: 0.05, type 2 error: 0.20 (Power: 80%), a difference of 10 in the average value of both groups, a standard deviation (SD) of 34 for both groups (the highest SD observed during the validation of the SF-36 domains (Lugo et al., 2006). The correlation between basal and follow-up measurements was fixed at 0.5.

The minimal sample size for each group was 137. There was a total of 274 patients. The researchers anticipated that locating patients would be difficult due to high mobility. Therefore, an oversampling of 50% was performed, obtaining a final sample of 411 patients, of which only 293 could be contacted. The sample for the healthcare provider offering the RPP consisted of 148 patients, and the sample for the healthcare provider offering conventional treatment consisted of 145 patients. This guaranteed the expected representativeness.

The SF-36 consists of eight domains that were calculated by transforming the ordinal scale of the form's items into the corresponding score from 0 to 100 (Lugo et al., 2006). This model has been used to dene two summary scores, namely: the physical health summary score (PCS1) and the mental health summary score (MCS1). Each of these two components includes four SF-36 dimensions as follows: PCS1 includes physical functioning (PF), rolephysical (RP), body pain (BP) and general health (GH); MCS1 includes: vitality (V), social functioning (SF), role-emotional (RE) and mental health (MH). Furthermore, summary scores for physical and mental health were calculated using the same method applied in a reproducibility study of the SF-36 summary scores in HRQOL assessments for Schizophrenia patients (Leese et al., 2008).

Physical functioning (PF) is measured by assessing the ability to perform different kinds of simple and strenuous activities. Role physical (RP) is measured based on how much patients can devote themselves to their jobs and other activities. Bodily pain (BP) is measured based on pain intensity and on how it hinders daily work. General Health (GH) refers to the patients' assessment of their own health. Vitality (V) is measured by assessing the perception of energy, exhaustion, or fatigue. Social functioning (SF) is measured by observing how much the patients' health problems affect their social activities. Role emotional (RE) is measured in terms of what activities the patients stop doing due to emotional problems. Mental health (MH) is measured by assessing how nervous, sad, calm, discouraged, or happy the patients feel. Change in health has a scale which is independent from the aforementioned domains and is used to assess the health state of patients. The current health state is compared with the one exhibited by the same individual one year prior to the measurement.

Upon receiving the patient's informed consent, the SF-36 was administered by qualified medicine students. Also, its correct administration was verified and double data entry was used to ensure reliability.

One year later the total number of patients surveyed with the SF-36 was 133 for the RPP and 130 for CT. For the second application of the SF-36, data analysis was carried out assigning zero to the domains of deceased patients and imputing the remaining missing values through multiple linear regression (Alisson, 2001).

After imputing the domains, summary scores were calculated and their distribution explored using the Kolmogorov-Smirnov test to verify the normality assumption. A comparison was made between the HRQOL values obtained in the two measurements for each group. For this

Health-Related Quality of Life in Chronic Renal Predialysis

stages (1 and 2=12.4%). See Table 1.

with ES=0.11 (See Table 2).

(p=0.044; ES=0.19).

Domains and summary scores

**3.2 Perception of health-related quality of life** 

Patients Exposed to a Prevention Program – Medellín, 2007-2008 435

(Md=68) was found in the RPP group. Clinical parameters such as arterial pressure, serum creatinine, and body mass index showed no significant differences between the study groups. For the CT group, serum hemoglobin values were significantly higher, and the glomerular filtration rate was lower. Most patients in both healthcare providing institutions had a history of arterial hypertension (90%) and dyslipidemia (60%). Distribution by stages showed that patients joined the Renal Protection Program at early stages of their condition (1 and 2=29.7 %), whereas CT patients requested treatment when their disease was at later

At the start of the study, the perception of HRQOL measured by the SF-36 showed no significant differences between the RPP and CT, except for MCS1 and role-emotional. However, the effect size (ES) was 0.08 and 0.13 respectively. The only domain exhibiting significant differences after one year was change in health, whose values favored the RPP

As for the changes within each group after one year, the RPP patients showed a significant decrease only in physical functioning (p=0.038; ES=0.14), whereas CT patients showed a decrease in four domains: physical functioning (p=0.027; ES=0.14), general health (p=0.001; ES=0.29), social functioning (p=0.010; ES=0.22), and vitality (p=0.009; ES=0.22) and in MCS1

PCS1: 60.9 (28.4) 58.5 (27.6) 0.470 58.9 (27.6) 54.2 (28.7) 0.160 Physical Functioning 70.0 (27.4) 68.7 (26.4) 0.662 65.8 (30.6) 64.3 (31.1) 0.684 Role-Physical 62.0 (41.4) 63.3 (42.9) 0.795 66.4 (42.3) 59.7 (45.5) 0.191 Bodily Pain 66.7 (28.6) 67.8 (27.4) 0.733 65.0 (28.3) 64.2 (29.1) 0.808 General Health 58.8 (23.6) 60.4 (22.4) 0.554 57.6 (23.5) 53.1 (26.0) 0.125 MCS1: 67.1 (33.2) 75.1 (28.1) 0.027 69.4 (27.6) 69.7 (27.4) 0.917 Mental Health 69.6 (26.8) 73.3 (23.8) 0.219 68.1 (24.5) 69.8 (23.8) 0.539 Role-Emotional 64.8 (43.1) 76.0 (37.1) 0.017 71.0 (40.9) 70.1 (40.4) 0.858 Social Functioning 76.3 (29.1) 80.9 (27.0) 0.160 77.3 (26.6) 74.5 (28.5) 0.390 Vitality 67.4 (27.0) 67.8 (24.6) 0.905 64.9 (24.9) 61.9 (26.3) 0.315 Changes in Health 66.1 (23.9) 65.9 (21.1) 0.955 68.5 (23.2) 62.6 (22.9) 0.029

RPP: Renal Protection Program. CT: Conventional treatment; PCS1: Physical health summary score.

Table 2. Distribution of HRQOL scores in patients with chronic renal failure in predialysis

MCS1: Mental health summary score. SD: Standard deviation

before and after an intervention. Medellín, 2007-2008.

Initial 1 year RPP CT: t-Student RPP CT: t-Student Mean (SD) Mean (SD) P value Mean (SD) Mean (SD) P value

purpose, the t-student test for independent samples or the Mann-Whitney U test were used. Likewise, the changes in HRQOL values within each group were compared using the t test for related samples or Wilcoxon's rank sum test. The report was generated by analyzing the means in order to establish comparisons between our results and the scientific literature.

For each summary score and dimension of the HRQOL perceived after one follow-up year, the adjusted mean was calculated to compare both interventions using an analysis of covariance model (ANCOVA) and a two-way analysis of variance adjusted for gender and history of hypertension, diabetes and dyslipidemia. The ANCOVA's covariables were: the HRQOL scores obtained at the start of the study, age, and stage of the condition. Furthermore, the effect size of HRQOL differences was calculated using Cohen's effect size index and its corresponding Hedges' bias correction formula (Cohen, 1988). All analyses were conducted using the program SPSS version 15.
