04-연정훈

대한응급의학회지제 25 권제 6 호 Volume 25, Number 6, December, 2014 원 저 Medical 응급실에내원한지역사회획득폐렴노인환자에서적혈구크기분포폭의예후예측능력 가톨릭대학교의과대학응급의학교실 연정훈 김수현 윤준성 박규남 Red Cell Distribution width in Older Patients with Community-acquired Pneumonia in the Emergency Department Jeong Hoon Yeon, M.D., Soo Hyun Kim, M.D., Ph.D., Chun Song Youn, M.D., Kyu Nam Park, M.D., Ph.D. Purpose: Red cell distribution width (RDW) is a quantitative measure of variability in the size of circulating erythrocytes. Recent studies have shown that higher RDW is associated with increased mortality risk in patients with several diseases. In particular, community-acquired pneumonia (CAP) is a prevalent and potentially life-threatening infection and has poor prognosis in older patients. We investigated the association of RDW in older patients with CAP. Methods: We conducted a retrospective analysis study during the period from May, 2013 to October, 2013. Patients older than 65 who were treated with CAP in our emergency department were included in this study. We divided the two groups by RDW 14.5%, the best cutoff value for mortality by receiver operating curve (ROC) analysis. The primary outcome was in-hospital mortality. APACHE II, SOFA, PSI Class, and CURB 65 were calculated. Multivariate logistic regression analysis was performed to determine the risk factors for mortality. Results: A total of 569 patients were analyzed and overall mortality was 10.2%. Mean age was 76.7 years and range of RDW was 10.5%~26.2%. There were 208 patients above 14.5%. Significant differences in in-hospital mortality were observed between the two groups (15.0% vs. 22.1%, respectively). In multivariate logistic regression analysis, 책임저자 : 김수현서울특별시서초구반포대로 222 가톨릭대학교서울성모병원응급의학과 Tel: 02) 2258-1990, Fax: 02) 2258-1997 E-mail: emksh77@gmail.com 접수일 : 2014년 6월 30일, 1차교정일 : 2014년 6월 30일게재승인일 : 2014년 9월 29일 667 RDW>14.5% showed an association with mortality (OR=2.08, 95% CI 1.03-4.19). In ROC analysis, area under the curve of RDW was 0.716 (95%CI, 0.677-0.753). Conclusion: RDW at admission is associated with in-hospital mortality in older patients with CAP; and it might be a prognostic marker for mortality of CAP in older patients in the emergency department. Key Words: Red cell distribution width, Pneumonia, Mortality, Elderly Department of Emergency Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea Article Summary What is already known in the previous study Higher RDW is associated with increased mortality risk in patients with several diseases. In particular, in adult patients with CAP, elevated RDW levels on admission are associated with significantly higher rates of mortality and severe morbidity. What is new in the current study Among older patients with CAP, elevated RDW at admission is associated with in-hospital mortality; and it might be a prognostic marker for mortality of CAP in older patients in the emergency department. 서 현대의학의발전으로기대수명이늘어나면서전세계적으로노인인구의비율이증가되고노인들의질병에대한연구가이루어지고있다. 2000년우리나라전체인구중 65세이상노인인구의비율은 7.2% 이었고, 2013년현재 12.2% 로증가추세를보이고있다. 그리고향후 2030년에는 24.3%, 나아가 2050년에는 37.4% 를넘을 론

668 / 대한응급의학회지 : 제 25 권제 6 호 2014 것으로전망된다 1). 이와비례하여응급실에내원하는노인환자의비율역시증가하고있는상황이다. 미국의경우 2005년에응급실로내원한전체환자의 14.5% 가 65세이상노인이었고 2030년에는전체환자의 25% 를차지할것으로전망되었다 2). 지역사회획득폐렴 (community-acquired pneumonia, 이하 CAP) 은전세계적으로사망률과이환율에서가장주요한원인이다. 특히 CAP는 65세이상노인인구에서입원율이나이가들수록점점의미있게증가되는질환이고또한다른질환과비교하여높은사망률과이환율을가지는질환으로나타났다 3,4). 특히우리나라노인환자에서 CAP는사망원인중 3위를차지하고있다 1). 이렇듯노인환자에서폐렴이주요사망원인인점을감안하면폐렴으로진단된노인환자를응급실에서정확하게진단하고질환중증도를파악하여위험을예측하는것은치료계획을세우도예후를향상시키는데도움이될것이다. 이에따라임상적인판단뿐만아니라환자를객관적으로평가할수있는여러생화학적지표들이함께사용되고있다. 적혈구크기분포폭 (Red cell distribution width, 이하 RDW) 은적혈구의형태와사이즈의다양성을측정한것으로주로빈혈을감별진단할때주요한지표로쓰여졌다. 그러나최근연구에따르면 RDW는심장질환이나뇌혈관, 류마티스성관절염, 패혈증, 심지어고관철수술후사망률의예측인자로도연구되고있다 5-9). 빈혈외에 RDW가증 가하는이유는아직명확하게밝혀지지는않았다. 하지만염증상반응이나산화스트레스에의해발생할것으로예측되고있다 10). 최근몇몇연구에서는성인전체환자및젊은환자들을대상으로이러한 RDW가 CAP의사망률예측과관련이있다고발표하기도하였다 11,12). 이에연구자들은응급의료센터에내원하여 CAP로진단된 65세이상노인환자에서내원초기 RDW를측정하고분석하여사망률과의연관성이있는지를분석하고, 다른예후예측지표들과비교함으로써환자의예후를예측하는데도움이되는지여부를알아보고자하였다. 대상과방법 1. 연구대상 2013년 5월부터 2013년 10월까지 6개월간가톨릭대학교서울성모병원응급의료센터에내원한 65세이상의모든노인환자중 CAP로진단된환자를대상으로후향적분석연구를시행하였다. 본기관은 1300침상규모의 3차의료기관으로연간응급의료센터환자수는약 6만명이다. 연구는본의료기관의임상윤리심의위원회의승인을받고이루어졌다. 연구대상의포함기준은나이만 65세이상이고비외상성질환으로응급의료센터를방문한환자중방문 Fig. 1. Flow chart of patients enrolled in this study.

연정훈외 : 응급실에내원한지역사회획득폐렴노인환자에서적혈구크기분포폭의예후예측능력 / 669 당시국제질병분류제 10판 (International Classification of Disease 10th Edition, ICD-10) 의 R04-06, R09, R509, A150-169, J00-06, J10-19, J20-22, J40-45, J61-64, J69, J80-86 에해당하는코드가하나라도있는환자들중발열이나기침, 가래등의호흡기증상이동반되며흉부단순방사선촬영상새로운폐침윤을보여 CAP의진단기준에부합하는경우로하였다. 이중내원초기응급의료센터에서혈액검사를시행하지않은환자, 다른병원에서전원온환자, 10일이내에병원에입원했던환자, 인체면역결핍바이러스질환자, 혈액질환이있는환자는연구대상에서제외하였다 (Fig. 1). 닌, 나트륨, 칼륨, 혈색소, 백혈구수, 글라스고우혼수척도등을이용하여자동계산프로그램을통해 0부터 71점까지측정하였다 13). SOFA 점수는호흡기계, 신경계, 심혈관계, 신장계및혈청빌리루빈측정, 출혈성경향여부등에대한각각의점수를산정하여계산하였다 14). 대상환자에서 21가지의 PSI의인자를검토하여점수를계산하였으며대상환자가모두 65세이상이었기때문에 70점이하, 71~90, 91~130, 130점이상의군이각각 2단계로부터 5단계까지로분류하였다 15). CURB-65는의식상태, 혈중요소농도, 호흡수및혈압을측정하여 0점에서 5점까지나누어분류하였다 15). 2. 자료수집 4. 통계분석 환자들의영상의학과기록및전자의무기록을바탕으로하여자료를수집하였다. 환자의일반적정보로나이, 성별, 기저질환으로암, 당뇨, 고혈압, 뇌혈관질환, 심혈관질환, 만성신장질환, 폐질환유무를조사하였다. 환자의체온, 심박수, 호흡수, 수축기및이완기혈압등의신체활력징후는환자의응급의료센터내원시처음으로측정한기록을조사하였다. 연구대상인환자들은응급실내원초기첫번째혈액검사의결과중 RDW 검사결과를수집하였으며, 자동혈액분석기 (Sysmex XE-2100, Sysmex, Kobe, Japan) 에의해 RDW를포함한일반혈액검사를시행하였다. 본원의 RDW의참고치는 11.5% 에서 14.5% 까지이었다. 환자들의혈액검사결과에서 RDW 외에백혈구, 혈색소, 적혈구용적, 평균적혈구용적, 적혈구침강속도, C-반응단백질, 혈당, 혈중요소질소, 크레아티닌, 나트륨결과와동맥혈액을이용한수소이온농도, 산소분압의수치를수집하였다. 모든연구대상환자들은흉부방사선촬영을시행하였고, 이의분석은영상의학과의사의판독기록에의해이루어졌다. 연구대상에포한된모든환자들의응급의료센터내원시부터응급센터퇴실및병원퇴원까지의기록을조사하였고, 원내사망여부를확인하였다. 이외에중환자실입원여부, 중환자실재원일수, 승압제사용여부및인공호흡기적용여부를조사하였다. 3. 중증도지표수집된데이터로부터모든환자들의임상중증도지표인 Acute Physiology and Chronic Health Evaluation (APACHE) II 점수, The Sequential Organ Failure Assessment score (SOFA) 점수, 폐렴중증지수 (Pneumonia Severity Index, 이하 PSI) 및 CURB-65와같은중증도지표를계산하였다. APACHE II 점수는환자의나이, 응급실내원초기에측정한체온, 중심동맥압, 심박수, 호흡수, 등의신체활력징후와함께동맥수소이온농도, 크레아티 수집된자료의통계분석은 SPSS software, version 17.0 (SPSS, Chicago, IL, USA) 과 MedCalc 12.0 (MedCalc Software, Inc., Mariakerke, Belgium) 을이용하였고, p값이 0.05 미만인것을통계적으로유의한것으로해석하였다. RDW는사망에대한수신자조작특성곡선 (Receiver operating characteristic curve, ROC curve) 에의한이상절사값 14.5% 를기준으로두개의군으로나누어비교하였다. 연속변수에대해서는정규성검정후정규분포를보이는변수들에대해평균과표준편차로표현하고독립 t-검정을이용하였다. 명목변수에대해서는빈도와백분율로표현하였고, Pearson 카이제곱검정을이용하였다. 사망률과관련된예측인자의분석을위해단변량로지스틱회귀분석을시행하였으며이후유의한인자를다변량로지스틱회귀분석하여예후와의독립적상관관계를살펴보았다. 또한 CAP의중증도지표와 RDW의 ROC 분석을통해곡선하면적 (area under the curve, AUC) 을구하여 CAP의예후예측을위한표지자로서의유용성을평가하였다. 결과 1. 일반적특성연구기간동안본원응급의료센터에내원한 65세이상노인환자는모두 4,994명이었다. 이들중연구대상에포함된환자는총 569명이었고이중입원중사망한환자는총 58명 (10.2%) 이었다. 전체대상환자의평균나이는 76.7세였으며이중남성이 346명 (60.8%) 이었다. 연구대상환자들의 RDW의범위는 10.5% 에서 26.2% 까지로나타났다.

670 / 대한응급의학회지 : 제 25 권제 6 호 2014 2. 14.5% 보다낮은 RDW 군과높은 RDW 군의임상적특성 (Table 1) RDW 가 14.5% 보다낮은군과높은군은각각 361 명, 208명으로나타났다. 양군의평균연령은각각 76.8세와 76.6세로유의한차이는없었으며, 남성의비율역시차이가없었다. 그러나 RDW가 14.5% 보다높은군에서기저 질환중암, 만성신장질환과심부전을가진환자가유의하게많았으며, 심박수가빠른것으로나타났다. 혈액검사결과중헤모글로빈, 헤마토크릿수치, 혈중요소질소, 크레아티닌및적혈구침강속도가양군간에통계적으로유의한차이를보였다. Table 1. Baseline characteristics by low and high RDW groups. RDW 14.5% RDW>14.5% n=361 n=208 Male, n (%) 215 (59.6) 131 (63.0) <0.420 Age, mean±sd 76.8±7.8 76.6±7.0 <0.839 Premorbid disease, n (%) Neoplastic disease 084 (23.3) 098 (47.1) <0.001 Diabetes mellitus 126 (34.9) 080 (38.5) <0.395 Hypertension, 231 (64.0) 131 (63.0) <0.810 Coronary artery disease 056 (15.5) 034 (16.3) <0.793 Cerebrovascular accident 049 (13.6) 029 (13.9) <0.902 Congestive heart failure 018 (05.0) 021 (10.1) <0.020 Chronic kidney disease 037 (10.2) 034 (16.3) <0.034 Pulmonary disease 106 (29.4) 063 (30.3) <0.816 Vital sign, mean±sd Systolic blood pressure, mmhg 129.9±26.4 127.9±29.9 <0.392 Diastolic blood pressure, mmhg 074.4±16.1 073.3±18.1 <0.442 Heart rate, /min 091.0±21.3 094.9±20.6 <0.033 Respiratory rate, /min 20.6±2.9 21.1±4.0 <0.125 Temperature, C 37.1±0.9 37.0±0.8 <0.276 Laboratory finding White blood cell ( 10 9 /L) 10.1±4.4 09.7±4.5 <0.244 Hemoglobin (mg/dl) 12.6±2.1 11.2±2.3 <0.001 Hematocrit (%) 36.8±6.1 33.5±6.8 <0.001 Mean corpuscular volume 92.5±4.9 92.7±7.4 <0.727 Glucose (mg/dl) 158.2±88.4 160.2±93.3 <0.797 BUN (mg/dl) 025.0±16.9 032.5±26.3 <0.001 Creatinine (mg/dl) 01.3±1.2 02.1±2.6 <0.001 Sodium (meq/l) 136.8±6.40 137.2±5.80 <0.443 C-reactive protein (mg/dl) 05.7±8.2 06.5±7.5 <0.253 Erythrocyte sedimentation rate (mm/h) 051.2±32.0 067.3±37.2 <0.001 ph 07.4±0.1 07.4±0.1 <0.721 po 2, mmhg 074.9±20.7 077.2±29.8 <0.384 APACHE II 9.0 (7.0-11.0) 12.0 (9.0-15.0) <0.001 SOFA 2.0 (1.0-3.0)0 3.0 (2.0-5.0) <0.001 CURB-65 1 157 (43.5) 070 (33.7) <0.001 2 181 (50.1) 101 (48.6) 3 020 (05.5) 031 (14.9) 4 003 (00.8) 006 (02.9) PSI III 074 (20.5) 011 (05.3) <0.001 IV 198 (54.8) 098 (47.1) V 089 (24.7) 099 (47.6) RDW: red cell distribution width, BUN: blood urea nitrate, ph: hydrogen ion concentration, po2: partial pressure of Oxygen, APACHE II: acute physiology and chronic health evaluation II, SOFA: the sequential organ failure assessment score, PSI: pneumonia severity index p

연정훈외 : 응급실에내원한지역사회획득폐렴노인환자에서적혈구크기분포폭의예후예측능력 / 671 3. 14.5% 보다낮은 RDW 군과높은 RDW 군의환자결과 (Table 2) RDW 가 14.5% 보다높은군일수록입원치료를하는비 율이높았으며 (60.9% vs. 76.0%) 이중입원중사망하는환자는각각 17명과 41명으로의미있는차이를보이고있었다 (4.7% vs. 19.7%, p<0.001). 또한 RDW가 14.5% 보다높은군의환자들이중환자실입원및집중치료의적용을많이받는것으로나타났다. 병원입원기간은양군에서각각평균 8.0일과 10.8일로차이를보인반면 (p=0.001), 중환자실입원기간은 RDW가 14.5% 보다높은환자들이 1.9일로길었으나통계적으로유의하지는않았다 (p=0.054). 4. 로지스틱회귀분석결과 (Table 3) 단변량로지스틱회귀본석결과나이, 암병력, 호흡수, 헤마토크릿및혈중요소질소수치와 RDW가병원내사망에유의한예후예측인자로나타났으며, 각각의중증도지표또한병원내사망에유의한예측인자로분석되었다. 이들변수를통해시행한다변량로지스틱회귀분석에서는암병력 (Odds ratio 3.49, p=0.002), APACHE II (OR 1.23 p<0.001), RDW (OR 2.08 p=0.042) 가독립적인상관관계가있는것으로나타났으며, CURB-65의경우 1점군에비해 2점인군과 4점인군의오즈비 (OR) 가각각 2.8과 7.93으로유의하게나타났다. 5. RDW 및중증도지표와병원내사망률 양군에서 APACHE II 점수는각각중앙값 9.0점과 12.0점이었고, SOFA 점수중앙값은 2.0점과 3.0점으로유의한차이를보였다 (Table 1). 각각의 APACHE II 점수, SOFA 점수, PSI 단계및 CURB-65는그점수가높아짐에따라환자의사망률도높은것으로나타났다. 또한 각각의지표에따른사망률을세분하여살펴보면대부분높은 RDW 군의사망률이높은것으로분석되었다. 특히, APACHE II 점수가 10점미만이고 RDW가 14.5% 이하인환자들의사망률은 0.4% 인데비해 APACHE II 점수가 20점초과이고 RDW가 14.5% 초과인환자들의사망률은 72.7% 로나타났다. 또한 PSI 단계에따른사망률은낮은 RDW 군에서각각 PSI IV 단계는 2.0%, PSI V단계는 14.6% 의사망률을보인반면, 높은 RDW 군의사망률은각각 13.3%, 28.3% 로차이를보였다 (Fig. 2). 6. RDW와중증도지표 ROC 분석결과 RDW의곡선하면적은 0.716 (95% CI, 0.677-0.753) 이었고, 병원내사망에대한 RDW의이상적절사값은 14.5% 였으며, 이를기준으로하여민감도 67.3% (95% CI 63.1-71.4), 특이도 70.7% (95% CI 57.3-81.9), 양성예측도 95.3% (95% CI 92.6-97.2), 음성예측도 19.7% (95% CI 14.5-25.8) 를나타내었다. 이밖에다른중증도지표인 APACHE II 점수, SOFA 점수, PSI 단계및 CURB-65의 AUC는각각 0.866, 0.713, 0.734 및 0.690으로나타났다. RDW는 APACHE II 점수와는 AUC 의유의한차이를보였으나 (p<0.001), 나머지지표들과는통계적으로유의한차이를보이지않았다 (Fig. 3). 고찰노인인구에서 CAP는종종패혈증과관련이있고, 이환율과사망률을보이는주요질환중의하나로알려져있다 16). 노인에서의면역력저하는 CAP를발생하게하는주요원인중의하나가되고, 이러한기전에의해발생한 CAP는개발도상국을비롯한전세계적으로매우심각하고비용이많이발생하게되는질환으로남게된다 17). 이에 CAP의중증도판단이질병의치료에있어매우중요한부분으로이 Table 2. Comparisons of outcome in patients with community-acquired pneumonia between the low and high RDW groups. RDW 14.5% RDW>14.5% n=361 n=208 Primary outcome In-hospital mortality, n (%) 017 (4.7)0 041 (19.7) <0.001 Secondary outcome Hospitalization, n (%) 220 (60.9) 158 (76.0) <0.001 ICU admission, n (%) 054 (15.0) 046 (22.1) <0.031 Hospital days, mean (95% CI) 8.0 (6.9-9.1) 10.8 (9.0-12.6) <0.011 ICU LOS, days, mean (95% CI) 1.1 (0.7-1.4) 1.9 (1.2-2.7) <0.054 Vasopressor use, n (%) 022 (6.1)0 028 (13.5) <0.003 Mechanical Ventilator use, n (%) 018 (5.0)0 023 (11.1) <0.007 RDW: red cell distribution width, CI: confidence interval, ICU: intensive care unit, LOS: length of stay p

672 / 대한응급의학회지 : 제 25 권제 6 호 2014 는질병의예후를예측하여관련된사망을감소시키는데도움을주게된다. 특히노인환자들은사망률이나합병증발생이젊은성인에비해훨씬높다고알려져있다 18). 항생제치료나중환자치료분야의발전에도불구하고여전히노인환자군에서사망률및이환율은여전히높고, 이에노인환자에서 CAP의예후증대를위해서는질병의중증도를파악하여적절한치료가일찍시작될수있도록하는노력이필요한것이다. 응급실에내원하는 CAP 환자들에게서일반혈액검사는기본혈액검사로쉽고빠르게시행할수있고그결과또한변이가크지않다. RDW는이러한일반혈액검사의일부항목으로마찬가지로쉽게알아낼수있는결과이다. 본연구에서는노인폐렴환자의중증도지표로서 RDW를이용했는데, 이는적혈구의크기나모양의변이정도를살펴보는검사로주로빈혈의감별진단을위해중요한지표로사용되어왔다. 그러나최근 RDW는여러질환의예후와관련 Table 3. Univariate and multivariate logistic regression analysis for in-hospital mortality of old aged patients with community acquired pneumonia. Univariate Multivariate OR (95% CI) p OR (95% CI) p Age 0.98 (0.95-1.00) <0.041 0.97 (0.93-1.03) <0.321 Male 1.54 (0.65-3.65) <0.326 Neoplastic disease 4.84 (2.73-8.60) <0.001 3.49 (1.55-7.85) <0.002 Diabetes mellitus 0.68 (0.28-1.07) <0.120 Hypertension 0.79 (0.45-1.37) <0.404 Coronary artery disease 0.47 (0.18-1.22) <0.121 Cerebrovascular accident 0.44 (0.15-1.24) <0.121 Congestive heart failure 1.32 (0.50-3.53) <0.575 Chronic kidney disease 0.96 (0.42-2.20) <0.921 Pulmonary disease 0.81 (0.44-1.50) <0.500 Systolic blood pressure, mmhg 0.97 (0.96-1.01) <0.128 Diastolic blood pressure, mmhg 1.02 (0.99-1.06) <0.203 Heart rate, /min 1.00 (0.99-1.02) <0.820 Respiratory rate 1.09 (1.02-1.17) <0.014 1.05 (0.96-1.14) <0.276 Temperature, C 0.91 (0.67-1.23) <0.535 White blood cell ( 10 9 /L) 1.04 (0.98-1.10) <0.173 Hemoglobin (mg/dl) 0.71 (0.26-1.94) <0.503 Hematocrit (%) 0.95 (0.91-0.99) <0.008 1.01 (0.96-1.06) <0.701 Mean corpuscular volume 1.03 (0.98-1.07) <0.244 Glucose (mg/dl) 1.00 (1.00-1.00) <0.917 BUN (mg/dl) 1.01 (1.00-1.02) <0.022 0.98 (0.97-1.00) <0.085 Creatinine (mg/dl) 0.96 (0.82-1.13) <0.634 Sodium (meq/l) 0.96 (0.90-1.03) <0.275 C-reactive protein (mg/dl) 1.01 (0.96-1.07) <0.694 Erythrocyte sedimentation rate (mm/h) 1.00 (0.99-1.01) <0.807 ph 0.12 (0.01-2.01) <0.140 po 2, mmhg 1.00 (0.99-1.01) <0.683 RDW>14.5% 4.97 (2.74-9.01) <0.001 2.08 (1.03-4.19) <0.042 APACHE II 1.33 (1.24-1.42) <0.001 1.23 (1.11-1.38) <0.001 SOFA 1.29 (1.15-1.44) <0.001 1.05 (0.86-1.29) <0.610 PSI class IV reference reference V 4.58 (2.51-8.34) <0.001 1.40 (0.61-3.20) <0.429 CURB-65 1 reference reference 2 2.88 (1.34-6.21) <0.007 2.80 (1.10-7.12) <0.030 3 09.17 (3.70-22.70) <0.001 2.70 (0.75-9.70) <0.127 4 030.28 (6.93-132.23) <0.001 07.93 (1.08-58.35) <0.042 OR: odds ratio, CI: confidence interval, BUN: blood urea nitrogen, RDW: red cell distribution width, APACHE II: acute physiology and chronic health evaluation II, SOFA: the sequential organ failure assessment score, PSI: pneumonia severity index

연정훈외 : 응급실에내원한지역사회획득폐렴노인환자에서적혈구크기분포폭의예후예측능력 / 673 Fig. 2. In-hospital mortality by RDW groups and disease severity scales. Fig. 3. Receiving operating characteristic curve and AUC of the disease severity scales to predict in-hospital mortality.

674 / 대한응급의학회지 : 제 25 권제 6 호 2014 된지표로보고되고있다 19-22). 특히심혈관질환과관련된연구에서는 RDW의증가에따른예후에대한위험비율은 1.8에서 8.6에이르기까지다양하게보고되고있다. 또한 Aung 등 8) 은심부전환자 274명을대상으로한연구에서 RDW가증가하는경우주당사망률 1% 증가를예측하는위험비율이 9.27이라고보고하기도하였다. 이러한심혈관질환외에말초혈관질환, 뇌혈관질환, 급성신손상및폐동맥고혈압등의질환에서 RDW는유용한사망예측도구라고알려져왔다 6,23-25). 특히중증질환자에서 RDW는매우강력하게사망률과관련이있다고밝혀져있다 5). 이와같이 RDW는다른다양한질환에서질환의사망률및중증도의예측인자로유용성이입증되고있다. 최근 Braun 등 11) 은 CAP로입원한성인환자들을대상으로한연구에서 RDW와높은사망률과이환율이높은관련이있다고발표하였다. 그러나노인환자들은기저질환이나병의진행과정이일반성인환자들과다르기때문에본연구에서는노인환자들만을대상으로하여연구를진행하였다. 또한 Patel 등 26,27) 은 RDW가질병여부와관계없이노인에서의사망률을예측하는강력하고도간단한지표라고하였고, 질병이없는 1,603명의노인에서전체사망률에대한위험비를 1.32라고하였으며, 질환여부와관계없이전체노인환자들의사망률과관련하여 1% RDW 가증가하는경우사망위험은 14% 증가한다고하였다. 이와같은노인환자군에서진행한본연구의다중로지스틱회귀분석결과에의하면많은위험인자들중, 암병력, APACHE II, CURB-65 점수와 RDW>14.5% 군인경우각각독립적으로사망과관련이있는것으로나타났다. 이들위험인자중특히 RDW가 14.5% 보다높은경우사망위험은 2.08배나높은것을추정할수있었다. RDW의증가가폐렴환자에서나쁜예후와관련되는기전은알려지지않았다. 다만, 염증반응체계의활성화와관련된민감한지표가되기때문일것이라는설명이있는데, 염증에노출되어반응한사이토카인의분비과정과관련되어적혈구생성인자의활성을막고, 적혈구숙성을방해하여부적절한적혈구의생성을유발하게되어 RDW를증가시키게될것이라는것이다 10). 몇몇연구에서이미급성염증성질환또는감염상태에서 C-반응단백이나적혈구침강속도등의염증관련인자들의증가와 RDW의증가와상관관계가있다고밝힌바있다 28). 그러므로내원초기 RDW의증가는심한염증반응을반영한다고볼수있으므로, CAP 환자의나쁜예후를나타내는중증도지표가될수있을것이다. 최근의연구에따르면 PSI 단계나 CURB-65 점수등이 CAP 환자들의예후를예측하고위험도를파악하는데도움을준다고하였으며, 이와더불어 APACHE II 점수는중환자실에입원한환자들의사망률예측에폭넓게유용되고있는점수체계로 CAP 환자에서도적용가능한중증도 지표라할수있다 13,29). 본연구의 ROC 분석결과에서중증도지표인 APACHE II 점수, SOFA 점수, PSI 단계및 CURB-65 점수의 AUC는각각 0.866, 0.713, 0.734 및 0.698이었고, CURB-65 점수의 AUC가상대적으로다른지표에비해낮은것으로나타났다. RDW는 AUC 0.716, PPV( 양성예측도 ) 95.3% 로다른중증도지표와비슷한수준의예후예측정도를보이는지표인것으로생각되었다. 그러나중증도파악을더욱명확히하기위한분석을통해, 각각의지표들을단독으로사용하기보다는 PSI 단계단독혹은 CURB-65 점수단독에비해 RDW를추가할때 30일사망률예측의가치를개선시킬수있다고보고하기도하였다 12). 본연구에는몇가지제한점이있다. 첫째본연구가일개지역응급센터에내원한환자를대상으로했기때문에연구결과가대외적타당성을가진다고확신할수없다. 둘째는본연구는후향적연구로서연구결과에영향을줄수있는여러변수들의조절이이루어지지않는등의기술적한계점을가지고있다. 셋째로환자의병원입원도중사망률만조사하여장기예후와의관련성을평가하지못했다는것이다. 향후연구에서는전향적, 그리고다기관연구를통해 RDW와질환의사망률및중증도지표로서의가치를살펴보는것이필요할것이다. 결 응급의료센터에내원하는 CAP 노인환자에서 RDW의증가는환자의나쁜예후와관련이있었으며, 환자의사망률을예측하는지표로서중증도지표와도비슷한가치를보였다. 그러므로 CAP로진단된 65세이상노인환자에서응급실내원초기검사한 RDW는환자의중증도를파악하는데도움을줄수있을것이며, 이는치료방향결정에도움을주어환자의예후를향상시키는결과를가져올수있을것이다. 론 참고문헌 01. Available at: http://www.kostat.go.kr/. Accessed May 10, 2013. 02. Nawar EW, Niska RW, Xu J. National Hospital Ambulatory Medical Care Survey: 2005 emergency department summary. Adv Data. 2007;386:1-32. 03. Fry AM, Shay DK, Holman RC, Curns AT, Anderson LJ. Trends in hospitalizations for pneumonia among persons aged 65 years or older in the United States, 1988-2002. JAMA. 2005;294:2712-9. 04. Garibaldi RA. Epidemiology of community-acquired res-

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