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Influence of Needle Gauge in Mantoux Skin Testing
Influence of Needle Gauge in Mantoux Skin Testing* Patricia M. Flynn, M.D.; jerry L. Shenep, M.D.; Lian Mao, M.S .; Rosemary Crawford, R.N.; Bonnie F. Williams, R.N.; and Bobby G. Williams, B.S. Study objective: To determine the influence of needle gauge in Mantoux skin testing for tuberculosis. Design: Randomized selection of either a 27- or 30gauge needle for Mantoux skin test placement; observer-blinded. Setting: Annual hospital employee screening. Participants: Six hundred twenty-five employees working in clinical and laboratory research environments. Results: Blinded observers found that the use of 27gauge needles caused increased bleeding and bruising compared with 30-gauge needles (p::S0.007 for each). However, the 27-gauge needle produced larger blebs
The Mantoux skin test is currently the most reliable indicator of infection with Mycobacterium tuberculosis. While considerable attention has been focused on consistency in interpreting the skin test, methods for administration of the test have received little notice. The American Thoracic Society, the Centers for Disease Control and Prevention (CDC), 1 and the manufacturer of tuberculin purified protein derivative (PPD) solution recommend use of a 26- or 27-gauge needle for applying the test (as noted in the package insert for Tuberculin Purified Protein Derivative [Mantoux] Tubersol, Connaught Laboratories Ltd, Willowdale, Ontario, Canada). Nevertheless, some centers currently are using smaller bore (30-gauge) needles for this procedure. Some healthcare providers believe that the 30-gauge needle is easier to insert intradermally and causes less pain and trauma . The purpose of this study was to determine the effect of needle gauge in the delivery of PPD administered via Mantoux testing. MATERIALS AND METHODS
In our annual screening for tuberculosis, Mantoux skin tests were administered to 625 employees with previously negative skin tests at St. Jude Children's Research Hospital. Tests were administered during a 2-day campaign by three nurses experienced in administering intradermal tests. Tuberculin PPD (Tubersol) was supplied in 10-dose vials. Syringes containing 0.1 ml *From the Departments of Infectious Diseases and Biostatistics, St./ude Children's Research Hospital (Mss. Crawford and B.F. Wi Iiams; and Mr.s Mao and B.C. Williams), and the Department of Pediatrics, University of Tennessee (Drs. Flynn and Shenep), Memphis, Tenn. Supported in part by National Cancer Institute Cancer Center Support (CORE) grant P30CA21765 and the American Lebanese Syrian Associated Charities (ALSAC). Manuscript received December 28, 1993; revision accepted March 29, 1994. Reprint requests: Dr. Flynn, 332 N. Lauderdale, Memphis, TN 38133
and less leakage of tuberculin solution (p::S0.0003).
Conclusion: Smaller gauge needles could potentially cause false-negative screening results because of decreased antigen delivery. Use of needle gauges smaller than 27 gauge should be avoided until their reliability is validated. Chest 1994; 106:1463-65)
I PPD=purified protein derivative I Key words: employee health; Mantoux test; PPD; purified protein derivative; tuberculosis of PPD were filled on site and administered within 1 h. Employees were assigned to receive their injections with a 27- or 30-gauge needle according to the terminal digit of their employee number (odd numbers were assigned 27-gauge and even numbers 30gauge needles). The vials of PPD were accessed using 27-gauge needles. The same needle was used to administer the skin test in those subjects assigned to the 27-gauge group. In the other study group, the 27-gauge needle was replaced with a 30-gauge needle before administration. Each nurse administered approximately equal numbers of skin tests using 27- and 30-gauge needles. The resulting bleb was assessed immediately by two investigators (P.M.F. and J.L.S.) who did not know the needle gauge used. The size of the bleb was measured to the nearest millimeter, and the amount of tuberculin solution leakage or blood at the injection site was recorded (each judged as none, minimal, moderate, or large) . Subjects were questioned as to whether the pain experienced with the injection was less, the same, or more compared with their previous experience with Mantoux skin tests. After 48 to 72 h, 501 employees (80 percent) returned for reading of their skin tests. Statistical analysis of the data was performed using the Wilcoxon rank sum test. The significance level of each individual test was adjusted for multiple comparisons to control the experimentwise type 1 error rate at 0.05. In order for a comparison to be declared statistically significant, the observed probability value had to be less than 0.0073. RESULTS
Although both needles yielded a median bleb size of 8 mm, overall the 27-gauge needle yielded larger blebs than the 30-gauge needle (Table 1: p==0.0003; mean, 8.5 vs 8.1 mm) . Concordantly, there was significantly less leakage of PPD with the 27 -gauge needle (Table 2: p<0.0001). There was less bleeding and bruising associated with the use of the 30-gauge needle (Table 2: p==0.007 and 0.004, respectively). The level of pain experienced when 27 -gauge needles were used was not significantly different from that when 30-gauge needles were used (Table 2: p==O.Ol5). Of the 501 employees returning for skin test readings, CHEST /106/5/ NOVEMBER, 1994
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Table !-Effect of Mantoux Test Needle Gauge on Bleb Size*
Table 3-Effect of Mantoux Test Needle Gauge on Induration
Needle Size 27-Gauge
Induration 30-Gauge
Bleb Size, mm
Frequency
%
0 3 4 5 6 7 8 9 10 11 12 13 Total
2 3 3 13 48 89 63 49 25 5 2 303
0.33 0.66 0.99 0.99 4.29 15.84 29.37 20.79 16.17 8.25 1.65 0.66 100
Frequency 0 4 8 22 65 110 58 42 12 0 0 322
%
0 0.31 1.24 2.48 6.83 20.19 34.16 18.01 13.04 3.73 0 0 100
*Wilcoxon rank sum test, probability value=0.0003.
three had induration of 10 mm or greater. All three of these employees had had their test administered with a 27-gauge needle (p=O.ll; Fisher's exact test). The induration difference associated with use of the two needles did not reach statistical significance (Table 3: p=0.20). DISCUSSION
There are many potential sources of inconsistency in delivering PPD via the Mantoux method, including adsorption of PPD to the vial or to the syringe used to administer the skin test. 2 Other potential pitfalls include inaccurate measurement of solution to be injected and loss of antigen in the dead space of the needle. The amount of antigen delivered can be crucial in detecting persons infected with M tu-
27-gauge 30-gauge
0-4
5-9
~10
Total
233 251
6 8
3 0
242 259
Probability Value* 0.20
*Wilcoxon rank sum test.
berculosis. Furcolow et aP found that the percentage of positive skin test reactors was proportional to the dosage of tuberculin administered. Snider2 noted that the injection of too little antigen was a potential cause of false-negative tuberculin reactions. In this study, we have shown that the needle gauge used also can affect the size of the bleb produced, resulting in leakage of the injected solution, and, consequently, can affect the amount of PPD antigen delivered to the Mantoux test recipient. The larger bleb size and decreased leakage associated with the use of 27-gauge needles was an unexpected finding. Our expectation had been that a smaller needle would lead to less leakage of tuberculin solution and increased exposure to antigen. However, the use of smaller bore needles apparently resulted in less dispersion of the tuberculin solution in the tissues, leading to more leakage than occurred with the use of 27 -gauge needles. It is possible that some loss of antigen in the needle dead space may have occurred for a few patients in the 30-gauge group when replacing the 27-gauge needle used to access the vial of PPD. While this could explain a smaller bleb size, it is contradictory to the increased leakage observed with the 30-gauge needles. In accord with our expectations, production of more bleeding and bruising was associated with the larger
Table 2-Effect of Mantoux Test Needle Gauge on Test Solution Leakage, Bleeding, Bruising, and Pain No. of Employees (%) Scoring -1 Observation Leakage* 27-gauge 30-gauge Bleeding* 27-gauge 30-gauge Bruising* 27-gauge 30-gauge Paint 27-gauge 30-gauge
71 (23.4) 106 (32.9)
0
2
87 (28.7) 61 (18.9)
160 (52.8) 128 (39.8)
51 (16.8) 116 (36.0)
210 (69.3) 253 (78.6)
85 (28.0) 65 (20.2)
8 (2.7) 4 (1.2)
143 (59.1 ) 183 (70.7)
85 (35.1) 70 (27.0)
11 (4.6) 6 (2.3)
212 (70.0) 197 (61.2)
20 (66) 19 (5.9)
3
5 (1.7 ) 17 (53)
3 (1.2)
No. of Employees
Probability Value !
303 322
<0.0001
303 322
0.007
242 259
0.004
303 322
0.015
*Scale: O=none; 1=mild; 2=moderate; 3=large. fScale: -l=less than usual; O=same as usual; 1=more than usual. !Wilcoxon rank sum test.
1464
Influence of Needle Gauge in Mantoux Skin Testing (Flynn et alj
bore needle. In conclusion, we found that a 27-gauge needle delivered a larger volume of tuberculin solution than did a 30-gauge needle. It can be argued that the difference, although statistically significant, has little clinical relevance because both needle gauges produced acceptable bleb size, according to current guidelines, in the majority of cases. However, it is possible that smaller gauge needles that deliver less antigen may fail to identify a patient with tuberculosis who would have been identified as positive by standard testing. We therefore believe further inves-
tigation in large populations with a high prevalence of M tuberculosis infection is necessary before use of needles smaller than 27 -gauge can be sanctioned. REFERENCES
1 Bass JB Jr, Farer LS, Hopewell PC, Jacobs RF, Snider DE Jr. American Thoracic Society. Diagnostic standards and classification of tuberculosis. Am Rev Respir Dis 1990; 142:725-35 2 Snider DE, Jr. The tuberculin skin test. Am Rev Respir Dis 1982; 125:108-18 3 Furcolow ML, Hewell B, Nelson WE, Palmer CE. Quantitative studies of the tuberculin reaction. Public Health Rep 1941; 56:1082-1100
CHEST /106/5/ NOVEMBER, 1994
1465
The Mantoux skin test is currently the most reliable indicator of infection with Mycobacterium tuberculosis. While considerable attention has been focused on consistency in interpreting the skin test, methods for administration of the test have received little notice. The American Thoracic Society, the Centers for Disease Control and Prevention (CDC), 1 and the manufacturer of tuberculin purified protein derivative (PPD) solution recommend use of a 26- or 27-gauge needle for applying the test (as noted in the package insert for Tuberculin Purified Protein Derivative [Mantoux] Tubersol, Connaught Laboratories Ltd, Willowdale, Ontario, Canada). Nevertheless, some centers currently are using smaller bore (30-gauge) needles for this procedure. Some healthcare providers believe that the 30-gauge needle is easier to insert intradermally and causes less pain and trauma . The purpose of this study was to determine the effect of needle gauge in the delivery of PPD administered via Mantoux testing. MATERIALS AND METHODS
In our annual screening for tuberculosis, Mantoux skin tests were administered to 625 employees with previously negative skin tests at St. Jude Children's Research Hospital. Tests were administered during a 2-day campaign by three nurses experienced in administering intradermal tests. Tuberculin PPD (Tubersol) was supplied in 10-dose vials. Syringes containing 0.1 ml *From the Departments of Infectious Diseases and Biostatistics, St./ude Children's Research Hospital (Mss. Crawford and B.F. Wi Iiams; and Mr.s Mao and B.C. Williams), and the Department of Pediatrics, University of Tennessee (Drs. Flynn and Shenep), Memphis, Tenn. Supported in part by National Cancer Institute Cancer Center Support (CORE) grant P30CA21765 and the American Lebanese Syrian Associated Charities (ALSAC). Manuscript received December 28, 1993; revision accepted March 29, 1994. Reprint requests: Dr. Flynn, 332 N. Lauderdale, Memphis, TN 38133
and less leakage of tuberculin solution (p::S0.0003).
Conclusion: Smaller gauge needles could potentially cause false-negative screening results because of decreased antigen delivery. Use of needle gauges smaller than 27 gauge should be avoided until their reliability is validated. Chest 1994; 106:1463-65)
I PPD=purified protein derivative I Key words: employee health; Mantoux test; PPD; purified protein derivative; tuberculosis of PPD were filled on site and administered within 1 h. Employees were assigned to receive their injections with a 27- or 30-gauge needle according to the terminal digit of their employee number (odd numbers were assigned 27-gauge and even numbers 30gauge needles). The vials of PPD were accessed using 27-gauge needles. The same needle was used to administer the skin test in those subjects assigned to the 27-gauge group. In the other study group, the 27-gauge needle was replaced with a 30-gauge needle before administration. Each nurse administered approximately equal numbers of skin tests using 27- and 30-gauge needles. The resulting bleb was assessed immediately by two investigators (P.M.F. and J.L.S.) who did not know the needle gauge used. The size of the bleb was measured to the nearest millimeter, and the amount of tuberculin solution leakage or blood at the injection site was recorded (each judged as none, minimal, moderate, or large) . Subjects were questioned as to whether the pain experienced with the injection was less, the same, or more compared with their previous experience with Mantoux skin tests. After 48 to 72 h, 501 employees (80 percent) returned for reading of their skin tests. Statistical analysis of the data was performed using the Wilcoxon rank sum test. The significance level of each individual test was adjusted for multiple comparisons to control the experimentwise type 1 error rate at 0.05. In order for a comparison to be declared statistically significant, the observed probability value had to be less than 0.0073. RESULTS
Although both needles yielded a median bleb size of 8 mm, overall the 27-gauge needle yielded larger blebs than the 30-gauge needle (Table 1: p==0.0003; mean, 8.5 vs 8.1 mm) . Concordantly, there was significantly less leakage of PPD with the 27 -gauge needle (Table 2: p<0.0001). There was less bleeding and bruising associated with the use of the 30-gauge needle (Table 2: p==0.007 and 0.004, respectively). The level of pain experienced when 27 -gauge needles were used was not significantly different from that when 30-gauge needles were used (Table 2: p==O.Ol5). Of the 501 employees returning for skin test readings, CHEST /106/5/ NOVEMBER, 1994
1463
Table !-Effect of Mantoux Test Needle Gauge on Bleb Size*
Table 3-Effect of Mantoux Test Needle Gauge on Induration
Needle Size 27-Gauge
Induration 30-Gauge
Bleb Size, mm
Frequency
%
0 3 4 5 6 7 8 9 10 11 12 13 Total
2 3 3 13 48 89 63 49 25 5 2 303
0.33 0.66 0.99 0.99 4.29 15.84 29.37 20.79 16.17 8.25 1.65 0.66 100
Frequency 0 4 8 22 65 110 58 42 12 0 0 322
%
0 0.31 1.24 2.48 6.83 20.19 34.16 18.01 13.04 3.73 0 0 100
*Wilcoxon rank sum test, probability value=0.0003.
three had induration of 10 mm or greater. All three of these employees had had their test administered with a 27-gauge needle (p=O.ll; Fisher's exact test). The induration difference associated with use of the two needles did not reach statistical significance (Table 3: p=0.20). DISCUSSION
There are many potential sources of inconsistency in delivering PPD via the Mantoux method, including adsorption of PPD to the vial or to the syringe used to administer the skin test. 2 Other potential pitfalls include inaccurate measurement of solution to be injected and loss of antigen in the dead space of the needle. The amount of antigen delivered can be crucial in detecting persons infected with M tu-
27-gauge 30-gauge
0-4
5-9
~10
Total
233 251
6 8
3 0
242 259
Probability Value* 0.20
*Wilcoxon rank sum test.
berculosis. Furcolow et aP found that the percentage of positive skin test reactors was proportional to the dosage of tuberculin administered. Snider2 noted that the injection of too little antigen was a potential cause of false-negative tuberculin reactions. In this study, we have shown that the needle gauge used also can affect the size of the bleb produced, resulting in leakage of the injected solution, and, consequently, can affect the amount of PPD antigen delivered to the Mantoux test recipient. The larger bleb size and decreased leakage associated with the use of 27-gauge needles was an unexpected finding. Our expectation had been that a smaller needle would lead to less leakage of tuberculin solution and increased exposure to antigen. However, the use of smaller bore needles apparently resulted in less dispersion of the tuberculin solution in the tissues, leading to more leakage than occurred with the use of 27 -gauge needles. It is possible that some loss of antigen in the needle dead space may have occurred for a few patients in the 30-gauge group when replacing the 27-gauge needle used to access the vial of PPD. While this could explain a smaller bleb size, it is contradictory to the increased leakage observed with the 30-gauge needles. In accord with our expectations, production of more bleeding and bruising was associated with the larger
Table 2-Effect of Mantoux Test Needle Gauge on Test Solution Leakage, Bleeding, Bruising, and Pain No. of Employees (%) Scoring -1 Observation Leakage* 27-gauge 30-gauge Bleeding* 27-gauge 30-gauge Bruising* 27-gauge 30-gauge Paint 27-gauge 30-gauge
71 (23.4) 106 (32.9)
0
2
87 (28.7) 61 (18.9)
160 (52.8) 128 (39.8)
51 (16.8) 116 (36.0)
210 (69.3) 253 (78.6)
85 (28.0) 65 (20.2)
8 (2.7) 4 (1.2)
143 (59.1 ) 183 (70.7)
85 (35.1) 70 (27.0)
11 (4.6) 6 (2.3)
212 (70.0) 197 (61.2)
20 (66) 19 (5.9)
3
5 (1.7 ) 17 (53)
3 (1.2)
No. of Employees
Probability Value !
303 322
<0.0001
303 322
0.007
242 259
0.004
303 322
0.015
*Scale: O=none; 1=mild; 2=moderate; 3=large. fScale: -l=less than usual; O=same as usual; 1=more than usual. !Wilcoxon rank sum test.
1464
Influence of Needle Gauge in Mantoux Skin Testing (Flynn et alj
bore needle. In conclusion, we found that a 27-gauge needle delivered a larger volume of tuberculin solution than did a 30-gauge needle. It can be argued that the difference, although statistically significant, has little clinical relevance because both needle gauges produced acceptable bleb size, according to current guidelines, in the majority of cases. However, it is possible that smaller gauge needles that deliver less antigen may fail to identify a patient with tuberculosis who would have been identified as positive by standard testing. We therefore believe further inves-
tigation in large populations with a high prevalence of M tuberculosis infection is necessary before use of needles smaller than 27 -gauge can be sanctioned. REFERENCES
1 Bass JB Jr, Farer LS, Hopewell PC, Jacobs RF, Snider DE Jr. American Thoracic Society. Diagnostic standards and classification of tuberculosis. Am Rev Respir Dis 1990; 142:725-35 2 Snider DE, Jr. The tuberculin skin test. Am Rev Respir Dis 1982; 125:108-18 3 Furcolow ML, Hewell B, Nelson WE, Palmer CE. Quantitative studies of the tuberculin reaction. Public Health Rep 1941; 56:1082-1100
CHEST /106/5/ NOVEMBER, 1994
1465