National Nosocomial Infections Surveillance (NNIS) Report, data summary from October 1986–April 1996, issued May 1996

SPECIAL

COMMUNICATION

National Nosocomial Infections Surveillance (NNIS) Report, Data Summary from October 1986-April 1996, Issued May 1996 A report from the National Nosocomial Infections Surveillance (NNIS) System* Hospital Infections Program, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Public Health Service, U.S. Department of Health and Human Services, Atlanta, Georgia

This report is a summary of the data collected by participating hospitals in the National Nosocomial Infections Surveillance (NNIS) System from October 1986 through April 1996 and updates previously published data.rM4 The NNIS System was established in 1970 when selected hospitals in the United States routinely began reporting their nosocomial infection surveillance data for aggregation into a national database. Hospitals participating in the NNIS System provide general medical-surgical inpatient services to adults or children requiring acute care. Identity of the 231 hospitals currently participating in NNIS hospitals is confidential. All NNIS data are collected by use of four standardized protocols, called surveillance components: hospital-wide (the only component until October 1986), adult and pediatric intensive care unit (ICU), high-risk nursery (HRN), and surgical may be used singly or patient. ‘p6 The components simultaneously, but once selected, they must be used for a minimum of 1 calendar month. All infections are categorized into major and specific infection sites by use of standard Centers for Disease Control and Prevention (CDC) definitions that include laboratory and clinical criteria.6-8 Hospital-wide surveillance component. Infection control practitioners (ICPs) following this component collect data on all sites of nosocomial infection for all patients. Infection rates are calculated This

report

is public

*See Appendix AJIC

Am J Infect

1 ?I52175860

380

domain

and can

C. Control

1996;24:380-8.

be copied

freely.

by service with hospital discharges or, optionally, patient-days as a denominator. Adult and pediatric ICU surveillance component. ICPs collect data on all sites of nosocomial infection in patients located in ICUs, as well as ICU-specific denominator data. Site-specific infection rates can be calculated by using as a denominator the number of patients at risk, total patient-days, and days of indwelling urinary catheterization, central vascular cannulation (central line), or ventilation. HRN surveillance component. ICPs collect data on all sites of nosocomial infection in patients located in HRN, as well as HRN-specific denominator data. Site-specific infection rates can be calculated by using as a denominator the number of patients at risk, total patient-days, and days of umbilical catheter/central line use or ventilation for each of four birth weight categories ( < 1000 gm, 1001 to 1500 gm, 1501 to 2500 gm, and > 2500 gm). Surgical patient surveillance component. ICPs select from the NNIS operative procedure list those procedures they wish to follow and monitor the patients undergoing those procedures for all infections or surgical site infections (SSI) only. A record on every patient undergoing the selected procedure is generated that includes information on risk factors for SSI such as wound class,’ duration of operation, and American Society of Anesthesiology (ASA) sc0re.l’ With a composite index used for predicting the risk of SSI after surgery, ICPs can calculate rates by number of risk factors present.4 The time periods for the data contained in this

AJIC

Volume 24, Number 5

NNIS Report

Table 1. Percentage distribution January 1990 to March 1996

of nosocomial All sites* n = 101,821 isolates

Pathogen Staphylococcus aureus Escherichia co/i

pathogens,

by infection

UTI n = 35,079 isolates

13 12

SSI n = 17,671 isolates

Other n = 21,214 isolates

0

1

1

2 1 0

2 1 0

1 2 0

Other Klebsiella spp. Other enterobacteriaceae-aerobes Other Gram-positive aerobes Viruses

1 1 1 1

1 1 0 0

1 1

1 0

1 1

1 1

2

1

0

0

0

1

Bacteroides

1

0

2

1

0

1 2 0

Gram-positive anaerobes Proteus

mirabilis

Other Streptococcus Other Candida Other fungi Acinetobacter spp.

spp.

Serratia marcescens Citrobacter spp.

Other nonenterobacteriaceae-aerobes Group D Streptococcus Group B Streptococcus Haemophilus

*Pathogens

influenzae

fragilis with less than 1% of the isolates

11 10 9 6 5 5 4 3 2 2 2

1

1

1

1

1 2

1 1

1 1

16 5 31 9 3 4 5 5 1 1 3 3 1 2 1 1

PNEU n = 13,433 isolates

1 1 1

staphylococci

Enterococcus spp. Pseudomonas aeruginosa Enterobacter spp. Candida albicans Klebsiella pneumoniae

20 8 14 12 8 7 3 3 1 3 3 1 0

BSI n = 14,424 isolates

Component,

19 4 2 2 17 11 5 8 0 2 1 1 1 4 3 1 4 0 1 5

Coagulase-negative

2 24 4 16 11 5 8 8 0 5 1 3 3

site, Hospital-wide

381

18 4 14 5 7 4 4 3 19 2 2 1 1 1 1 1 1 1 1 1

at all sites are not shown

report vary depending on the table. In general, if the rates have not changed from October 1986, when the surveillance components were first introduced, data from the entire time period were used in the table. If there was evidence of a change in the rates that are used for interhospital comparisons, a more recent, yet arbitrary, time period was selected. For example, some ICU rates were higher in the late 1980s than in the 1990s. Therefore the earlier data were not included in the tables. Each table represents NNIS data from one of the surveillance components. Table 1 shows the percentage distribution of the major pathogens isolated from nosocomial infection sites reported by hospitals using the Hospital-wide Component. These data are provided as a general overview of the distribution of pathogens from the major sites of infection but should not be used for interhospita1 comparison purposes because the data are not adjusted for infection risks in the patients. Table 2 from the ICU Component updates previously published device-associated rates. ‘r2 Note that the number of units reporting data from

the burn, respiratory, and trauma ICUs is still insufficient to provide percentile distributions of the rates. Table 3 provides information on device utilization (DU) by type of ICU. For the adult and pediatric ICU component, device-days consist of the total number of ventilator-days, central linedays, and urinary catheter-days. The DU of an ICU is one measure of the unit’s invasive practices that constitutes an extrinsic risk factor for nosocomial infection. As such, DU may also serve as a marker for severity of illness of patients in the unit, that is, patients’ intrinsic susceptibility to infection. Each of the analyses of NNIS ICU (and HRN) data excluded rates or DU ratios for units that did not report at least 50 patient-days or device-days. Because of this, the number of units contributing data in the tables is not exactly the same. Table 4 from the HRN Component updates the previously published, device-associated rates. ‘r3 In 1992, CDC subdivided the smallest birth weight category into two groups: I 1000 gm and 100 1 to 1500 gm. The rates for these birth weight categories are derived from data from January 1992 to April 1996. In addition, unlike the 199 1 published

AJIC

382

NNIS

Table

Report

October 1996

2A. Pooled means and percentiles

of the distribution of urinary catheter-associated rates,* by type of ICU, ICU Component, January 1990 to April 1996

infection

urinary tract Percentile

Type of ICU

No. of units

Coronary Medical Medical/surgical Neurosurgical Pediatric Surgical Burn Respiratory Trauma * Number

of urinary

Number

Urinary catheter-days

Pooled mean

10%

25%

so%t

75%

90%

193,543 372,731

8.0

0.0

3.5

6.6

10.6

15.6

8.7 5.8

1.6 0.7

4.4 3.2

7.8 5.7

9.8 8.4

13.1 11.1

9.7 5.8

2.7 0.7

5.0 2.7

8.0 5.0

10.2 9.1

14.4 11.9

5.6 8.2

0.2 -

2.4 -

4.8 -

7.1 -

9.3 -

7.3 8.8

-

-

-

-

-

89 91 172 30

737,066 105,555

53 145

104,003 750,472

14 5

16,671

15

77,179

14,078

catheter-associated

of urinary

UTls

catheter-days

x1000

tMedian.

Table

28. Pooled means and percentiles

of the distribution of central line-associated rates,* by type of ICU, ICU Component, January 1990 to April 1996

infection

primary

bloodstream

Percentile Type of ICU

No. of units

Coronary Medical Medical/Surgical Neurosurgical Pediatric Surgical Burn Respiratory Trauma * Number

of central

Number

Central line-days

Pooled mean

10%

25%

50%t

75%

90%

88 89

123,634 271,499

5.0 6.4

0.0 1.9

1.5 3.7

4.2 5.5

7.1 7.9

9.8 10.0

172 30

468,708 57,585

4.6 6.0

0.0 1.5

2.0 3.0

4.2 4.8

6.6 8.8

8.8 11.6

57 143

151,962 646,279

7.9 5.1 14.0

0.0 0.4 -

3.9 2.0 -

6.8 3.6 -

9.5 6.3

12.5 9.2 -

5.2 7.3

-

-

-

-

-

14 5

11,469 4802

15

59,136

line-associated

of central

BSls

line-days

x1000

tMedian.

Table

2C. Pooled means and percentiles of the distribution of ventilator-associated rates,* by type of ICU, ICU Component, January 1990 to April 1996

pneumonia

infection

Percentile Type of ICU

No. of units

Coronary Medical Medical/surgical

Neurosurgical Pediatric Surgical Burn

Respiratory Trauma * Number

tMedian.

Pooled mean

10%

25%

50%-l

75%

90%

81

80,385

9.9

0.0

4.7

8.1

13.8

18.2

89 171 30 58 143 14

260,838 369,529 51,344 159,715 423,748 9038

5 15

14,928 52,108

9.4 12.5 20.2 5.9 14.9 20.9 6.4 16.9

2.9 3.6 5.7 0.0 3.8 -

4.7 a.2 10.6 1.3 a.4 -

a.5 11.5 16.5 5.0 13.2 -

13.2 15.4 28.9 8.4 la.5 -

15.4 19.2 33.2 .11.6 25.5 -

of ventilator-associated Number

Ventilator-days

of ventilator-days

pneumonias

x , ooo

AJIC Volume

24,

Table

Number

3A.

NNIS

5

Pooled

and percentiles of the distribution January 1990 to April 1996

means

ICU, ICU Component,

of urinary catheter

utilization

Report

383

ratios,* by type of Percentile

Type of ICU

No. of units

Patient-days

Pooled mean

10%

25%

50%t

75%

90%

92 94 174 30 58

465,675 549,680 1,004,142 136,621 339,387

0.18

145

916,648

0.42 0.68 0.73 0.77 0.31 0.82 0.48 0.51 0.86

0.31 0.57 0.65 0.69 0.19 0.76 -

0.42 0.69 0.76 0.86 0.27 0.85 -

0.53 0.79 0.83 0.92 0.39 0.90 -

0.64 0.87 0.90 0.93 0.50 0.95 -

Coronary Medical Medical/surgical Neurosurgical Pediatric Surgical Burn Respiratory Trauma * Number

14 5 15

of urinary

Number

34,795 27,448 89,604

0.40 0.53 0.62 0.11 0.66 -

catheter-days

of patient-days

tMedian.

Table 38. Pooled means and percentiles of the distribution ICU Component, January 1990 to April 1996

of central line utilization

ratios,*

by type of ICU, Percentile

No. of units

Type of ICU

92 94

Coronary Medical Medical/surgical Neurosurgical Pediatric Surgical Burn Respiratory Trauma * Number

174 30 59 145 14 5 15

of central

Number

Patient-days

Pooled mean

10%

25%

50%t

75%

90%

465,675 549,680 1,004,142 136,621 339,387 916,648 34,795 27,448 89,604

0.27 0.49 0.47 0.42 0.45 0.71 0.33 0.17 0.66

0.11

0.23 0.24 0.26 0.26 0.49 -

0.17 0.32 0.33 0.38 0.33 0.60 -

0.25 0.48 0.49 0.47 0.42 0.71 -

0.35 0.57 0.59 0.57 0.55 0.81 -

0.49 0.72 0.73 0.72 0.63 0.89 -

utilization

ratios,*

lineedays

of patient-days

tMedian.

Table

3C.

Component,

Pooled

January

Type of ICU Coronary Medical Medical/surgical Neurosurgical Pediatric Surgical Burn Respiratory Trauma * Number Number tMedian.

of ventilator-days of patient-days

and percentiles 1990 to April 1996

means

No. of units 90 94 174 30 60 145 14 5 15

of the distribution

of ventilator

by type of KU, KU

Patient-days

Pooled mean

10%

25%

50%f

75%

90%

465,675 549,680 1,004,142 136,621 339,387 916,648 34,795 27,448 89,604

0.17

0.07 0.20 0.20 0.25 0.25 0.25 -

0.10 0.30 0.29 0.31 0.34 0.36 -

0.15 0.45 0.37 0.40 0.43 0.46 -

0.24 0.58 0.48 0.50 0.56 0.55 -

0.31 0.68 0.61 0.58 0.63 0.63 -

0.47 0.37 0.38 0.47 0.46 0.26 0.54 0.58

384

NNIS Report

Table

4.

categories,

October

Pooled means and percentiles of the distribution HRN Component, January 1990 to April 1996

of device-associated

infection

AJIC 1996

rates, by birth weight Percentile

Birth weight

No. of HRNs

Umbilical and central 5 1000 gm* 1001-1500 gm* 1501-2500 gm > 2500 gm Ventilator-associated 5 1000 gm* 1001-l 500 gm*

gm

1501-2500

z 2500

line-associated 83 77 81 84 pneumonia rate8 82 76 83 80

gm

Device-days

Pooled mean

10%

25%

50%*

75%

90%

113.0

4.1 1.6 0.0 0.0

8.6 3.5 1.8 0.0

12.2 6.1 5.5 3.7

17.6 12.7 8.9 7.1

23.1 17.7 14.0 10.2

4.9

0.0

4.2 3.6 2.9

0.0 0.0 0.0

1.5 0.0 0.0 0.0

3.4 2.5 2.0 0.7

7.5 5.7 4.0 3.8

10.6 9.0 7.4 6.8

BSI ratet 153,795 73,642 71,449 102,245 177,026 59,463 49,925 70,693

7.9 6.1 4.7

*Median. Number t *Data 0

of umbilical

and central

line-associated

Number

of umbilical

and central

for these

birth weight

categories

Number

of ventilator-associated Number

BSI

line-days begin in January

pneumonias

x 1000 1992.

x1000

of ventilator-days

Table 5. Pooled means and percentiles of the distribution categories, HRN Component, January 1990 to April 1996

of device

utilization

ratios, by birth weight Percentile

Birth weight

No. of HRNs

Umbilical and central 5 1000 gm* 1001-I 500 gm* 1501-2500

Pooled mean

10%

25%

50%*

75%

90%

93

402,873 289,862 336,791 327,448

0.38 0.25 0.21 0.31

0.17 0.08 0.04 0.07

0.27 0.12 0.08 0.17

0.35 0.23 0.17 0.22

0.51 0.39 0.31 0.40

0.61 0.52 0.53 0.55

87 87 93 93

402,873 289,862 336,791 327,448

0.44 0.21 0.15 0.22

0.23 0.07 0.03 0.05

0.33 0.11 0.07

0.42 0.17 0.12 0.15

0.55 0.28 0.19 0.24

0.66 0.45 0.37 0.40

line utilization 87 87

gm

ratiot

93

> 2500 gm Ventilator utilization 5 1000 gmf 1001-1500

Patient-days

ratio5

gm*

1501-2500 gm 5 2500 gm

o.ii

*Median. t

Number

of umbilical Number

*Data for these §

Number Number

and central

linedays

of patient-days

birth weight

categories

begin in January

1992

of ventilator-days of patient-days

rates, the rates for the four birth weight groups are no longer combined because the distribution for each rate differs by birth weight category. Table 5 provides the DU ratios for the HRNs. For the HRN Component, device-days consist of the total number of ventilator-days and umbilical catheter and central line-days. Table 6 from the Surgical Patient Component updates the previously published rates.‘v4 When the SSI rates for adjacent risk index categories for a particular procedure were not significantly

different, we combined them into a single risk index category. For example, because SSI rates for appendectomies with 2 or 3 risk factors were not significantly different, we combined the data into a new category 2,3 and reported one rate. Table 7 contains the percentile distributions of SSI rates by operative procedure and risk index category. For a hospital to be represented in this distribution, it must have reported sufficient data, that is, at least 30 operations in a given risk index category for the procedure. Note that the percen-

AJIC Volume 24, Number 5 Table 8. SSI rates,* by operative October 1986 to May 1995

Operative

CARD CBGB CBGC OCVS ORES THOR APPY BILI CHOL COLO GAST OGIT SB X!AP NEPH OGU PRST HN OENT HER MAST CRAN ONS VSHN CSEC HYST OOB VHYS AMP FUS FUSN LAM FX OMS PROS HPRO KPRO OPRO OBL OES OEYE OSKN SKGR SPLE TP vs

procedure category

Cardiac surgery CABG-chest & leg CABG-chest only Other cardiovascular system Other respiratory system Thoracic surgery Appendectomy Bile duct/liver/pancreas Cholecystectomy Colon surgery Gastric surgery Other digestive system Small bowel surgery Laparotomy Nephrectomy Other genitourinary Prostatectomy Head and neck Other eye, nose, throat Herniorrhaphy Mastectomy Craniotomy Other nervous system Ventricular shunt Cesarean section Abdominal hysterectomy Other obstetric procedures Vaginal hysterectomy Limb amputation Spinal fusionilaminectomyt Spinal fusion Laminectomy Open reduction of fracture Other musculoskeletal Joint prosthesist Hip prosthesis Knee prosthesis Other prosthesis Other hematologic/ lymphatic Other endocrine system Other eye Other integumentary system Skin graft Splenectomy Organ transplant Vascular surgery

NNIS Report procedure Duration cut point W)

and risk index category,

Risk index

N

Rate

Risk index

6833 628 1701 4118

1.76 1.11 1.88 0.70 4.01 0.58 1.18 2.65 0.72 4.22 3.14 2.02 5.50 2.05 1.83 0.52 0.83 1.85 0.47 0.97 1.15 1.41 1.52 3.90 3.37 1.57 0.60 0.85 4.86 0.90 1.32 0.70 0.89 0.72 1.13 0.74 0.84 0.71 0.77

5 5 5 2

0,1

1 3 1 4 2 3 3 3 3 2 3 2 4 5 2 2 2 5 3 2 1 2 1 2 1 3 4 2 2 3 3 2 2 2 3

0,12,3 0 0 0 0 0 0 0 0 0 0,123 0 0 0 O,l 0 0 051 ,Z3 0,1,2,3 0,123 0 0 0,123 0 0 0 0 0 O,l 0 0 O,l 0,1,2,3 0

1071 1041 3400 302 15,521 4053 1179 989 600 3359 1311 11,309 1211 703 2346 5744 3399 5739 I847 3054 31,263 12,346 331 4706 5079 17,963 2424 4124 6651 15,876 11,704 1896 4998 422 517

3 2 2

0 0,123 0,I 23

1158 1379 5915

2 2 7 3 -

0 O,l a1 0

828 630 883 2973

0 O,l O,l

0,123

-

Surgical

385

Patient Component,

N

Rate

2,3 I 2,3 2,3

1790 35,946 342 996

4.25 3.18 4.09 1.51

-

-

1 1 1 1 1 1 1 1 1

2528 3202 589 10,125 6640 2028 1348 1138 3435 -

1 1 1 2 1 1

1 1

Risk index

N

Rate

Risk index

N

Rate

5.39 -

-

-

-

-

2,3

8200 -

-

I .74 3.37 6.45 1.74 6.60 5.72 4.08 8.61 3.41 -

2,3 2,3 2,3 2 2 2,3 2,3 2,3 2,3

786 1175 268 2751 2978 821 426 758 1772 -

3.18 6.04 11.94 3.67 10.81 13.03 8.45 11.48 7.96 -

4172 941 689 215 3076 3551 -

1.20 2.66 4.21 2.79 1.89 1.86 -

2,3 2,3 2,3 3 2,3 2,3

859 178 281 15 500 466 -

4.77 5.62 12.10 20.00 3.40 4.72 -

12,262 6235

4.00 2.81

2,3 2,3

828 1131

7.00 6.10

1,2,3

2322 -

1.68 -

-

-

1 1 1 1 2,3 1 1,2,3 2,3

7273 1546 2650 8801 1263 10,587 4267 934 -

2.12 3.04 1.51 1.45 2.22 2.05 1.92 1.61 -

2,3 2,3 2,3 2

1601 417 792 1847 -

5.12 8.15 2.53 2.76 -

2,3

1230

4.88

-

-

1,2,3

475

2.74

-

-

0.17 0.15 1.69

123

783 -

1.15 -

-

-

1.21 2.38 4.87 1.38

1 2,3 2 1

1291 197 779 15,913

3.33 6.60 8.73 2.05

2

579 -

6.39 -

3 2

194 6492

20.10 5.33

-

-

280 310 -

5.71 15.48 -

-

-

-

-

170 -

5.29 -

-

-

3

118 -

11.02 -

3

188

12.23

3 3

3

Coronary artery bypass graft *Rate = No. SSI per 100 operations. tProcedure category not used in NNIS after June 1, 1994.

CABG,

tile distributions are not available for every operative procedure and risk index category because percentile distributions of the procedurespecific and risk-index-specific rates specific

rates required sufficient data from at least 20 hospitals. If you would like to compare your hospital’s rates and ratios with those in this report, you

386

NNIS Report

Table Surgical

October

7. Percentiles of the distribution of SSI rates,* by operative Patient Component, October 1986 to May 1995

procedure

AJIC 1996

and risk index category,t Percentile

Operative CARD CARD CBGB CBGB CBGC ocvs THOR APPY APPY APPY CHOL CHOL CHOL COLO COLO COLO GAST GAST XIAP XLAP X!AP OGU OGU HER HER MAST MAST CRAN VSHN CSEC CSEC HYST HYST HYST VHYS VHYS PRST AMP FUSD FUSO FUSQ FUSN FUSN LAM LAM FX FX FX OMS PROS5 PROS5 PROSO HPRO HPRO KPRO OSKN vs vs vs

procedure

surgery

Cardiac surgery Cardiac surgery CABG-chest & leg CABG-chest & leg CABG-chest only Other cardiovasc system Thoracic surgery Appendectomy Appendectomy Appendectomy Cholecystectomy Cholecystectomy Cholecystectomy Colon surgery Colon surgery Colon surgery Gastric surgery Gastric surgery Laparotomy Laparotomy Laparotomy Other genitourinary Other genitourinary Herniorrhaphy Herniorrhaphy Mastectomy Mastectomy Craniotomy Ventricular shunt Cesarean section Cesarean section Abdominal hysterectomy Abdominal hysterectomy Abdominal hysterectomy Vaginal hysterectomy Vaginal hysterectomy Prostatectomy Limb amputation Spinal fusion/laminectomy Spinal fusion/laminectomy Spinal fusion/laminectomy Spinal fusion Spinal fusion Laminectomy Laminectomy Open reduction of fracture Open reduction of fracture Open reduction of fracture Other musculoskeletal Joint prosthesis Joint prosthesis Joint prosthesis Hip prosthesis Hip prosthesis Knee prosthesis Other integumentary system Vascular surgery Vascular surgery Vascular surgery

Risk index

No. of hospitals

Pooled mean rate

10%

25%

50%*

75%

90%

45 26 78 56 33 23 28 28 31 22 65 69 40 41 52 36 21 27 26 31 24 30 25 32 32 32 34 38 27 69 59 52 47 21 28 25 20 32 56 54 20 23 24 37 38 41 54 27 37 61 63 21 26 45 46 25 31 54 50

1.76 4.25 3.18 5.39 1.88 0.70 1.74 1.18 3.37 6.04 0.72 1.74 3.67 4.22 6.60 10.81 3.14 5.72 2.05 3.41 7.96 0.52 1.20 0.97 1.89 1.15 1.86 1.41 3.90 3.37 4.00 1.57 2.81 6.10 0.85 1.68 0.83 4.86 0.90 2.12 5.12 1.32 3.04 0.70 1.51 0.89 1.45 2.76 0.72 1.13 2.05 4.88 0.74 1.92 0.84 1.69 1.38 2.05 5.33

0.00 0.00 0.45 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.13 0.00 4.55 0.00 1.08 0.00 0.00 0.38 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

0.00 2.12 1.86 3.40 0.00 0.00 0.00 0.00 1.71 1.00 0.00 0.00 0.99 1.88 3.13 6.12 0.00 1.92 0.43 1.11 4.55 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.17 1.48 0.00 0.00 3.60 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.60 0.00 0.00 0.00 0.00 0.00 0.00 1.76

1.14 4.55 2.94 4.83 0.00 0.00 0.99 0.00 3.38 4.76 0.32 1.48 2.97 4.27 5.36 9.30 2.04 4.17 1.60 3.22 6.25 0.31 0.56 0.45 0.96 0.29 0.97 0.84 3.53 2.52 3.27 1.09 1.77 5.19 0.39 1.17 0.00 3.49 0.69 1.61 3.85 0.29 2.27 0.00 0.00 0.00 0.93 2.13 0.45 0.84 1.80 4.55 0.00 1.61 0.00 1.13 0.00 1.53 5.19

2.17 7.26 3.86 7.93 2.82 0.87 2.70 1.85 5.89 6.83 1.05 2.50 5.26 6.08 8.52 15.96 5.24 6.97 2.91 5.38 13.21 0.83 1.92 1.60 3.08 1.72 2.49 1.53 4.97 5.43 6.56 2.31 3.77 7.63 1.45 2.54 1.61 5.26 1.57 3.05 5.41 2.07 3.25 0.97 2.07 1.16 1.82 3.25 1.23 1.83 3.10 7.06 1.20 2.54 1.41 2.07 1.46 2.74 7.45

2.81 9.82 5.65 10.75 6.04 1.82 3.77 3.63 7.08 8.15 1.68 3.25 6.56 8.69 11.05 16.86 6.73 10.88 4.82 8.20 14.91 2.46 2.74 2.05 5.19 3.51 5.09 2.58 6.18 7.33 9.45 5.00 4.63 8.31 2.08 3.95 3.45 7.47 2.24 6.25 11.54 2.54 9.41 1.68 3.21 1.81 2.93 6.71 1.88 3.82 4.84 9.77 1.96 3.53 2.1 2.69 2.21 3.90 9.52

a1

23 1

23 O,l 61 1 0 1

23 0 1 2 0 1 2 0 1 0 1

23 0 1 0 1 0 1

0,12,3 0,123 0 1 0 1

23 0

123 0

0,123 0 1

23 0 1 0 1 0 1 2 O,l 0 1

2,s 0 1,2,3 O,l 0,1.2,3 0 1 2

*Rate = No. SSI per 100 operations. tlncludes only those procedure-categories for which at least 20 hospitals *Median. §Procedure category not used in NNIS after June 1, 1994.

have reported

data.

AJIC Volume

24,

Number

NNIS

5

must first collect information from your hospital in accordance with the methods described for the NNIS System.‘s6 You should also refer to Appendixes A and B for further instructions. Appendix A discusses the calculation of infection rates and DU ratios for the ICU and HRN Surveillance Components. Appendix B gives a step-by-step method for interpretation of percentiles of infection rates or DU ratios. A high rate or ratio (> 90th percentile) does not necessarily define a problem; it only suggests an area for further investigation. Similarly, a low rate or ratio ( < 10th percentile) may be the result of inadequate infection detection. References 1. CDC NNIS System. National Nosocomial Infections Surveillance (NNIS) Semiannual Report, May 1995. AJIC Am J Infect Control 1995;23:377-85. 2. Jarvis WR, Edwards JR, Culver DH, et al. Nosocomial infection rates in adult and pediatric intensive care units in the United States. Am 3 Med 1991;91(suppl 3B):185S191s. 3. Gaynes RP, Martone WJ, Culver DH, et al. Comparison of rates of nosocomial infections in neonatal intensive care units in the United States. Am J Med 1991;91(suppl 3B):192S-196% 4. Culver DH, Horan TC, Gaynes RP, et al. Surgical wound infection rates by wound class, operative procedure, and patient risk index. Am J Med 1991;91(suppl 3B):152S157s. 5. Emori TG, Culver DH, Horan TC, et al. National nosocomial infections surveillance (NNIS) system: description of surveillance methodology. AJIC Am J Infect Control 1991;19:19-35. 6. Gaynes RP, Horan TC. Surveillance of nosocomial infections. In: Mayhall CG, ed. Hospital epidemiology and infection control. Baltimore: Williams and Wilkins, 1996: 1017-31, App-A-l-14. 7. Garner JS, Jarvis WR, Emori TG, Horan TC, Hughes JM. CDC definitions for nosocomial infections, 1988. AJIC Am J Infect Control 1988;16:128-40. 8. Horan TC, Gaynes RP, Martone WJ, Jarvis WR, Emori TG. CDC definitions of nosocomial surgical site infections, 1992: a modification of CDC definitions of surgical wound infections. Infect Control Hosp Epidemiol 1992; 13:606-8. 9. Garner JS. CDC guideline for prevention of surgical wound infections, 1985. Infect Control 1986;7:193-200. 10. Owens WD, Felts JA, Spitznagel EL Jr. ASA physical status classification: a study of consistency of ratings. Anesthesiology 1978;49:239-43.

APPENDIX A HOW TO A CALCULATE INFECTION RATE AND OR HRN COMPONENT

A DEVICE-ASSOCIATED A DU RATIO WITH ICU DATA

Calculation oE Device-associated, Device-day Infection Rate Step 1. Decide on the time period for your analysis. It may be a month, a quarter, 6 months, a year, or some other period. Step 2. Select the patient population for analysis, that is, the type of ICU or a birth weight category in the HRN.

Report

387

Step 3. Select the infections to be used in the numerator. They must be site-specific and must have occurred in the selected patient population. Their date of onset must be during the selected time period. Step 4. Determine the number of device-days that is used as the denominator of the rate. Devicedays are the total number of days of exposure to the device (central line, ventilator, or urinary catheter) by all of the patients in the selected population during the selected time period. Example:

In January 1996, five patients on the first day of the month had one or more central lines in place; five on day 2; two on day 3; five on day 4; three on day 5; four on day 6; and four on day 7. Adding the number of patients with central lines on days 1 through 7, we would have 5 + 5 + 2 + 5 + 3 + 4 +

4 = 28 central line-days for the first week. If we continued

for

the

entire

month,

the

number

of central

line-days for the month is simply the sum of the daily counts. Step 5. Calculate the device-associated, deviceday rate (per 1000 device-days) with the following formula: Device-associated,

device-day

rate =

Number of device-associated infections for a specific site Number

Example:

Central

of device-days

line-associated

BSI

rate

per

x 1000 1000

central line-days = Number of central line-associated Number of central line-days

BSI x 1000

Calculation of DU for an ICU or HRN Steps 1 to 4. Same as device-associated, deviceday rates plus determine the number of patientdays which is used as the denominator of the DU ratio. Patient-days are the total number of days that patients are in the ICU (or HRN) during the selected time period. Example:

In

January

1996,

10 patients were in the 12 on day 2; 11 on day 3; 13 on day 4; 10 on day 5; 6 on day 6; and 10 on day 7; and so on. If we counted the patients in the unit from day 1 through 7, we would add 10 i12 + 11 + 13 + 10 + 6 + 10 for a total of 72 patient-days for the first week of the month. If we

unit on the first day of the month;

continued for the entire month, the number of patient-days for the month is simply the sum of the daily

counts.

Step 5. Calculate the DU ratio with the following formula: DU

=

Number

of device-days

Number of patient-days

With the number of device-days and patientdays from above examples, DU = 28/72 = 0.39 or

TTTh

October

39% of patient-days were also central line-days for the first week of the month. Step 6. Examine the size of the denominator for your hospital’s rate or ratio. Rates or ratios may not be good estimates of the “true” rate or ratio for your hospital if the denominator is small, i.e., less than 50 device-days or patient-days. Step 7. Compare your hospital’s ICU/HRN rates or ratios with those found in the tables of this report. Refer to Appendix B for interpretation of the percentiles of the rates/ratios. APPENDIX B INTERPRETATION OF PERCENTILES INFECTION RATES OR DEVICE UTILIZATION RATIOS

OF

Step 1. Evaluate the rate (ratio) you have calculated for your hospital and confirm that the variables in the rate (both numerator and denominator) are identical to the rates (ratios) in the table. Step 2. Examine the percentiles in each of the tables and look for the 50th percentile (or median). At the 50th percentile, 50% of the hospitals have lower rates (ratios) than the median and 50% have higher rates (ratios). Step 3. Determine if your hospital’s rate (ratio) is above or below the median. Determining whether your hospital’s rate or ratio may be a HIGH outlier Step 4. If it is above the median, determine whether the rate (ratio) is above the 75th percentile. At the 75th percentile, 75% of the hospitals had Zower rates (ratios) and 25% of the hospitals had higher rates (ratios). Step 5. If the rate (ratio) is above the 75th percentile, determine whether it is above the 90th percentile. If it is, then your hospital may be a high outlier. Determining if your hospital’s rate or ratio may be a LOW outlier Step 6. If it is below the median, determine whether the rate (ratio) is below the 25th percentile. At the 25th percentile, 25% of the hospitals

had Zowev had higher Step 7. percentile, percentile. outlier.

AJIC 1996

rates (ratios) and 75% of the hospital rates (ratios). If the rate (ratio) is below the 25th determine whether it is below the 10th If it is, then your hospital may be a low

APPENDIX C NNIS PERSONNEL

Epidemiology Martin S. Favero, PhD Acting Director, Hospital Infections Program (HIP) Robert P. Gaynes, MD Chief, Nosocomial Infections Surveillance Activity (NISA), HIP Teresa C. Horan, MPH, CIC NNIS Coordinator, NISA, HIP T. Grace Emori, RN, MS Nurse Epidemiologist, NISA, HIP Leonardo A. Stroud, MD Medical Epidemiologist, NISA, HIP Lennox K. Archibald, MBBS, MRCP Epidemic Intelligence Service Officer, NISA, HIP Olivia Keita-Perse, MD Guest Researcher, NISA, HIP Gianna C. Wright, BA Secretary, NISA, HIP Statistics David H. Culver, PhD Chief, Statistics and Information Systems Branch (SISB), HIP Jonathan R. Edwards, MS Mathematical Statistician, SISB, HIP Tonya S. Henderson, BS Computer Specialist, SISB, HIP James S. Tolson, BS Computer Specialist, SISB, HIP Gloria E. Peavy Statistical Assistant, SISB, HIP