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A study of the relationship between tensile testing of condoms and breakage in use
CONTRACEPTION A STUDY OF THE RELATIONSHIP BETWEEN TENSILE TESTING OFCONDOMSANDBREAKAGEIN USE
John Gerofi BE, BSc, PhD’, Gergaynia Shelley Basil Donovan MBBS, DipVen, FACVen*
BA’,
‘Enersol Consulting Engineers, Annandaie, NSW, Australia *Director, Sydney STD Centre, Sydney Hospital, Sydney, Australia
ABSTRACT The ability of the condom wall to maintain its integrity throughout sexual intercourse is critical to its role in halting the spread of major sexually transmissible pathogens including the human immunodeficiency virus. There are three principal in vitro performance tests applied to condoms: a test for freedom from holes, an inflation test, and tensile testing. in this study we subjected condoms that had broken in use to tensile tests in order to determine any correlation between their in vivo and in vitro performance. Condoms which had broken in use showed similar tensile properties to those which had not. All passed all tensile test criteria. Thus, the inclusion of tensile testing in National Standards for condoms is not sufficient to insure strong products.
INTRODUCTION The’ consistent use of good quality condoms by those at risk forms an strategy against the spread of human important part of the immunodeficiency virus (HIV) and other sexually transmissible diseases (STDs). Clearly the ability of the condom wall to maintain its integrity throughout sexual intercourse is critical to this role. it is hoped that the performance of samples of condoms tested by in vitro methods reflect that integrity in vivo, though there is only limited evidence to support this assumption [l-3].
When condom testing was first introduced, the primary emphasis was on freedom from holes. Beginning in the 195Os, many brands were found More in independent tests to have a large proportion with holes. recently, reputable condom manufacturers have been supplying condoms Submitted for publication November 6, 1990 Accepted for publication January 4, 1991
FEBRUARY 1991 VOL. 43 NO. 2
177
CONTRACEPTION
of which almost none have holes and which easily meet standards requiring that fewer than 0.4% have holes [Donovan B, Richters J, Gerofi J, Watson L. A pharmacopoeia of Australian condoms. (Submitted)]. Thus intact condoms have proven impermeable to major STD pathogens in laboratory tests [4-IO]. Even when a small hole is present, it is arguable whether a sufficiently large inoculum would usually pass through it to infect (or render pregnant) another person.
Another recently adopted test for condoms is the inflation test. Like the test for freedom from holes, this test has been incorporated into the new International Standards Organisation (IS0 4074) Standard for condoms which was published in 1990. Variants of each of the above tests already form part of many national standards.
The inflation test requires that no more than a specified proportion of condoms burst below a certain volume or burst pressure when inflated with air. Proponents of the inflation test advocate it because: (a) it tests most of the condom rather than a small test piece (as occurs in tensile strength testing); (b) it is sensitive both to localized flaws in the rubber and to (more generalized) tensile properties; and (c) deteriorating performance in the test has been shown to correlate with ultra-violet deterioration of the condom and aging, as well as breakage in use [2,3].
Tensile testing of condom was adopted in many countries (but not Australia or Switzerland) as a measure of the strength of the rubber film. A tensile test involves cutting a sample from a condom and stretching it linearly until it breaks. Until now, no datahave been available to relate tensile measurement to failure during use. In this study, the relations between tensile properties and condom failure in vivo were explored by conducting tensile tests on condoms which had broken during anal intercourse.
STUDY
SAMPLE
AND METHODS
Samples of condoms As previously reported [ll], the collection of condoms broken in use was more difficult than high retrospectively reported breakage rates [12-141 might imply. As part of a prospective study, condom-using men attending one of two STD clinics or a student health service were asked
178
FEBRUARY 1991 VOL. 43 NO. 2
CONTRACEPTION to complete a questionnaire on possible risk factors for condom breakage. They were then provided with 48 condoms which had passed the Australian Standard [3]. They were also requested to personally return (in sealed containers) their first used and unbroken condom, as well as any condoms that broke in use. A combination of low breakage rates, patient embarrassment [15], and National Health and Medical Research Council Infection Control Guidelines that forbade posting the condoms, limited the number of condoms that were available for study.
All used condoms were gamma-irradiated (2.68 megarads) for infection control reasons. A control sample of unused condoms were also gamma-irradiated to determine any effect this process might have on the rubber. All condoms were from the same batch of the same brand. The six used and unbroken condoms were provided by six different men, while the eight broken condoms that were returned were provided by four different men. All had broken during anal intercourse. Three broken condoms had to be excluded because full-length tears precluded tensile testing according to the ISO, British and American Standard protocols, leaving five condoms that were tested.
Test
methods
In accordance with the American (ASTM D 3492), British (BS 3704), and International (IS0 4074) Standards, a 20mm wide annular circumferential (“ring”) section from the middle section of each eligible condom was tested. The condoms were powdered before cutting to prevent creasing, and the laboratory replaces blades in the cutting press every 60 cuts. As we had previously determined that most condom breaks in use occurred in the distal part of the condom (unpublished), whenever available a second “ring” section as near to the teat as possible was also tested. These sections were placed on a tensile testing machine and measured for tensile strength, force applied and elongation at break.
RESULTS All of the condoms, broken or intact, passed (Tables la and lb) the ISO, British and American Standards (Table II) on every tensile test criterion. Notably, the condoms which had broken in use tended to perform better than the three control groups on all parameters.
FEBRUARY
1991 VOL. 43 NO. 2
179
CONTRACEPTION
TABLE
la
The tensile characteristics of unused, used and unbroken, and used and broken condoms: Mean and Standard Deviation
(SD)
CONDOM CLASSIFICATION
Irradiated
control
irradiated, used, unbroken (n=8)
80.6
18.4
29.3
8.7
801
50
irradiated, used, broken (n=5)
93.7
8.4
36.3
3.1
833
20
MPa: megapascals
N: newtons
TABLE
lb
The tensile characteristics of unused, used and unbroken, and used and broken condoms: Range
CONDOM CLASSIFICATION
Force at Break (N)
Tensile Strength (MPa)
Elongation (W
Min
Max
Max
Min
Min
Max
Packed control (n=5)
55.4
67.8
24.0
32.5
760
802
Irradiated (n=6)
control
59.9
92.0
22.5
36.5
708
780
Irradiated, unbroken
used, (n=6)
Irradiated, used, broken (n=5)
FEBRUARY 1991 VOL. 43 NO. 2
CONTRACEPTION
TABLE IS0 (4074),
II
British (ES 3704:1989) and American (ASTM D 3492) Standards tensile testing of condoms (minimum requirements)
IS0 Force at break
British
American
(N)
New condoms
30
34
20.4
Aged condoms
30
30
16
New condoms
17
17
17
Aged condoms
17
15
15
New condoms
650
650
675
Aged condoms
650
630
625
Tensile
strength
Elongation
limits for
(MPa)
at break
(%)
The marginally higher mean scores of the irradiated condoms and lb) suggested that the condoms may have been slightly when packed.
(Tables la undercured
Data comparing middle of condom with “near-teat” samples from unused irradiated condoms and broken irradiated condoms are presented in Tables llla and Illb. There was a slight trend for the “near-teat” section of the broken condoms to compare unfavourably with the middle section of the same condom on all parameters. This occurred with every condom (Tables llla and Illb).
DISCUSSION Though the “ring” section is mandated by major Standards, some advocate using a “dumbbell” section of the wall of the condom. The “dumbbell” section is used for tensile testing thicker rubber articles and its proponents claim more uniform results than the “ring”. On the other difficult to measure with the hand, elongation at break is more “dumbbell”.
FEBRUARY 1881 VOL. 48 NO. 2
181
CONTRACEPTION TABLE
llla
Tensile characteristics of unused condoms and condoms broken in use: Middle versus near-teat sections (all irradiated): Mean and Standard Deviation
(SD)
More recently, Standards and specifications have tended to move toward favouring force at break rather than tensile strength. This is because tensile strength measurement requires measurement of the thickness of the condom wall, which is difficult with heavily textured condoms.
The size of the sample was limited by the availability of used, broken condoms. However, in routine practice, a batch of up to 100,000 condoms may be tensile tested utilizing as few as five condoms (IS02859 double sampling plan for reduced inspection and multiple sampling plans for normal inspection allow 5 and 3 condoms in the first sample). There is no reason to believe that the exduded condoms (with large tears) had significantly different tensile properties. Tears in thin rubber membranes (as opposed to well-formed holes) disseminate very rapidly once they have started. Thus a large tear would seem unlikely to indicate factors that were present before the condom ruptured, and is probably due to physical activity by the wearer after the initial tear.
The slight tendency for broken condoms testing of their distal parts as compared
182
not to score as well on tensile to their mid parts is of interest.
FEBRUARY 1991 VOL. 43 NO. 2
CONTRACEPTION TABLE Tensile
lllb
characteristics of unused condoms and condoms Middle versus near-teat sections (all irradiated):
Broken
broken Range
in use:
condoms
Further (and larger) studies finding. Nevertheless, even more appropriate for testing, sections from failed condoms Standards for tensile testing.
should be considered to investigate this if “near-teat” samples were found to be it is noteworthy that in this study these still all passed the current and proposed
Finally, it is self-evident that a good quality condom needs to be made from rubber with good tensile properties. Unfortunately, this study suggests that tensile testing does not offer any added assurance against a condom breaking in use. We could find no other study that has correlated the performance of condoms on tensile testing with condom failure in vivo. As the inflation test also stresses the condom, it alone may be sufficient to test condom strength.
For Australia it may be that limited resources would be better more systematic policing [4,17] of those condoms available Australian market rather than complicating the Standard.
FEBRUARY
1991 VOL. 43 NO. 2
spent on on the
183
CONTRACEPTION
ACKNOWLEDGMENTS This study is part of the Condom Project, University of Sydney, which was supported by a grant from the Commonwealth AIDS Research We thank Juliet Richters for coordinating the Grants Committee. Condom Project, Ansell International for providing condoms, as well as the staff and patients of the Taylor Square Private Clinic, Sydney STD Centre and the University Health Service at the University of Sydney for their kind co-operation.
REFERENCES 1. 2. 3.
4.
5. 6. 7.
8.
9.
10.
11. 12.
184
Condoms for the prevention of HIV Potts M, Short RV. transmission: cultural dimensions. AIDS 1989; 3: S259-63. Free MJ, Skiens EW, Morrow MM. Relationship between condom strength and failure during use. Contraception 1980; 22: 31-7. Free MJ, Hutchings J, Lubis F, Natakusumah R. An assessment of burst strength distribution data for monitoring quality of condom Contraception 1986; 33: 258-299. stocks in developing countries. Katznelson S, Drew WL, Mintz L. Efficacy of the condom as a barrier to the transmission of cytomegalovirus. J InfectDis 1984; 150: 155-7. Conant MA, Spicer DW, Smith CD. Herpes simplex virus transmission: condom studies. Sex Transm Dis 1984; 11: 94-5. Minuk GY, Bohme CE, Bowen TJ. Condoms and hepatitis B virus infection [letter]. Ann Intern Med 1986; 104: 584. Conant M, Hardy D, Sernatinger J, Spicer D, Levy JA. Condoms prevent transmission of AIDS-associated retrovirus. JAMA 1986; 355: 1706. Van de Perre P, Jacob D, Sprecher-Goldberger S. The latex condom, an efficient barrier against sexual transmission of AIDrelated viruses. AIDS 1987; 1: 49-52. Rietmeijer CAM, Krebs JW, Feorino PM, Judson FN. Condoms as physical and chemical barriers against human immuno-deficiency virus. JAMA 1988; 259: 1851-3. Judson FN, Ehret JM, Bodin GF, Levin MJ, Rietmeijer CAM. In vitro evaluations of condoms with and without nonoxynol as physical and chemical barriers against Chlamydia trachomatis, herpes simplex virus type 2, and human immuno-deficiency virus. Sex Transm Dis 1988; 16: 51-6. Richters J, Donovan B, Gerofi J, Watson L. Low condom breakage rate in commercial sex [letter]. Lancet 1988; 2: 1487-8. Van Griensven GJP, de Vroome EMM, Tielman RAP, Coutinho RA. Failure rate of condoms during anogenital intercourse in homosexual men. Genitourin Med 1988: 64: 344-6.
FEBRUARY 1991 VOL. 43 NO. 2
CONTRACEPTION 13. 14.
15.
16.
17.
Hatcher RA, Hughes MS. The truth about condoms. Siecus Report 1988; 17 (2): 1-9. Tindall B, Swanson C, Donovan B, Cooper DA. Sexual practices and condom usage in a cohort of homosexual men in relation to human immunodeficiency virus status. Med J Aust 1989; 151: 318-22. Lacey S. Honi Soit (University of Beware the condom kit. Sydney) 1989; 23: 17. Reprinted in Healthright 1989; (1): 20-l. Stube R, Voeller B, Davidhazy A. High Speed Cinematography of the initial break-point of latex condoms during the Air-burst Test. Contraception 1990; 6: 591-603. Australian Consumers Association. Condoms revisited. Choice 1989 (Jan): 42-5.
FEBRUARY 1991 VOL. 43 NO. 2
185
John Gerofi BE, BSc, PhD’, Gergaynia Shelley Basil Donovan MBBS, DipVen, FACVen*
BA’,
‘Enersol Consulting Engineers, Annandaie, NSW, Australia *Director, Sydney STD Centre, Sydney Hospital, Sydney, Australia
ABSTRACT The ability of the condom wall to maintain its integrity throughout sexual intercourse is critical to its role in halting the spread of major sexually transmissible pathogens including the human immunodeficiency virus. There are three principal in vitro performance tests applied to condoms: a test for freedom from holes, an inflation test, and tensile testing. in this study we subjected condoms that had broken in use to tensile tests in order to determine any correlation between their in vivo and in vitro performance. Condoms which had broken in use showed similar tensile properties to those which had not. All passed all tensile test criteria. Thus, the inclusion of tensile testing in National Standards for condoms is not sufficient to insure strong products.
INTRODUCTION The’ consistent use of good quality condoms by those at risk forms an strategy against the spread of human important part of the immunodeficiency virus (HIV) and other sexually transmissible diseases (STDs). Clearly the ability of the condom wall to maintain its integrity throughout sexual intercourse is critical to this role. it is hoped that the performance of samples of condoms tested by in vitro methods reflect that integrity in vivo, though there is only limited evidence to support this assumption [l-3].
When condom testing was first introduced, the primary emphasis was on freedom from holes. Beginning in the 195Os, many brands were found More in independent tests to have a large proportion with holes. recently, reputable condom manufacturers have been supplying condoms Submitted for publication November 6, 1990 Accepted for publication January 4, 1991
FEBRUARY 1991 VOL. 43 NO. 2
177
CONTRACEPTION
of which almost none have holes and which easily meet standards requiring that fewer than 0.4% have holes [Donovan B, Richters J, Gerofi J, Watson L. A pharmacopoeia of Australian condoms. (Submitted)]. Thus intact condoms have proven impermeable to major STD pathogens in laboratory tests [4-IO]. Even when a small hole is present, it is arguable whether a sufficiently large inoculum would usually pass through it to infect (or render pregnant) another person.
Another recently adopted test for condoms is the inflation test. Like the test for freedom from holes, this test has been incorporated into the new International Standards Organisation (IS0 4074) Standard for condoms which was published in 1990. Variants of each of the above tests already form part of many national standards.
The inflation test requires that no more than a specified proportion of condoms burst below a certain volume or burst pressure when inflated with air. Proponents of the inflation test advocate it because: (a) it tests most of the condom rather than a small test piece (as occurs in tensile strength testing); (b) it is sensitive both to localized flaws in the rubber and to (more generalized) tensile properties; and (c) deteriorating performance in the test has been shown to correlate with ultra-violet deterioration of the condom and aging, as well as breakage in use [2,3].
Tensile testing of condom was adopted in many countries (but not Australia or Switzerland) as a measure of the strength of the rubber film. A tensile test involves cutting a sample from a condom and stretching it linearly until it breaks. Until now, no datahave been available to relate tensile measurement to failure during use. In this study, the relations between tensile properties and condom failure in vivo were explored by conducting tensile tests on condoms which had broken during anal intercourse.
STUDY
SAMPLE
AND METHODS
Samples of condoms As previously reported [ll], the collection of condoms broken in use was more difficult than high retrospectively reported breakage rates [12-141 might imply. As part of a prospective study, condom-using men attending one of two STD clinics or a student health service were asked
178
FEBRUARY 1991 VOL. 43 NO. 2
CONTRACEPTION to complete a questionnaire on possible risk factors for condom breakage. They were then provided with 48 condoms which had passed the Australian Standard [3]. They were also requested to personally return (in sealed containers) their first used and unbroken condom, as well as any condoms that broke in use. A combination of low breakage rates, patient embarrassment [15], and National Health and Medical Research Council Infection Control Guidelines that forbade posting the condoms, limited the number of condoms that were available for study.
All used condoms were gamma-irradiated (2.68 megarads) for infection control reasons. A control sample of unused condoms were also gamma-irradiated to determine any effect this process might have on the rubber. All condoms were from the same batch of the same brand. The six used and unbroken condoms were provided by six different men, while the eight broken condoms that were returned were provided by four different men. All had broken during anal intercourse. Three broken condoms had to be excluded because full-length tears precluded tensile testing according to the ISO, British and American Standard protocols, leaving five condoms that were tested.
Test
methods
In accordance with the American (ASTM D 3492), British (BS 3704), and International (IS0 4074) Standards, a 20mm wide annular circumferential (“ring”) section from the middle section of each eligible condom was tested. The condoms were powdered before cutting to prevent creasing, and the laboratory replaces blades in the cutting press every 60 cuts. As we had previously determined that most condom breaks in use occurred in the distal part of the condom (unpublished), whenever available a second “ring” section as near to the teat as possible was also tested. These sections were placed on a tensile testing machine and measured for tensile strength, force applied and elongation at break.
RESULTS All of the condoms, broken or intact, passed (Tables la and lb) the ISO, British and American Standards (Table II) on every tensile test criterion. Notably, the condoms which had broken in use tended to perform better than the three control groups on all parameters.
FEBRUARY
1991 VOL. 43 NO. 2
179
CONTRACEPTION
TABLE
la
The tensile characteristics of unused, used and unbroken, and used and broken condoms: Mean and Standard Deviation
(SD)
CONDOM CLASSIFICATION
Irradiated
control
irradiated, used, unbroken (n=8)
80.6
18.4
29.3
8.7
801
50
irradiated, used, broken (n=5)
93.7
8.4
36.3
3.1
833
20
MPa: megapascals
N: newtons
TABLE
lb
The tensile characteristics of unused, used and unbroken, and used and broken condoms: Range
CONDOM CLASSIFICATION
Force at Break (N)
Tensile Strength (MPa)
Elongation (W
Min
Max
Max
Min
Min
Max
Packed control (n=5)
55.4
67.8
24.0
32.5
760
802
Irradiated (n=6)
control
59.9
92.0
22.5
36.5
708
780
Irradiated, unbroken
used, (n=6)
Irradiated, used, broken (n=5)
FEBRUARY 1991 VOL. 43 NO. 2
CONTRACEPTION
TABLE IS0 (4074),
II
British (ES 3704:1989) and American (ASTM D 3492) Standards tensile testing of condoms (minimum requirements)
IS0 Force at break
British
American
(N)
New condoms
30
34
20.4
Aged condoms
30
30
16
New condoms
17
17
17
Aged condoms
17
15
15
New condoms
650
650
675
Aged condoms
650
630
625
Tensile
strength
Elongation
limits for
(MPa)
at break
(%)
The marginally higher mean scores of the irradiated condoms and lb) suggested that the condoms may have been slightly when packed.
(Tables la undercured
Data comparing middle of condom with “near-teat” samples from unused irradiated condoms and broken irradiated condoms are presented in Tables llla and Illb. There was a slight trend for the “near-teat” section of the broken condoms to compare unfavourably with the middle section of the same condom on all parameters. This occurred with every condom (Tables llla and Illb).
DISCUSSION Though the “ring” section is mandated by major Standards, some advocate using a “dumbbell” section of the wall of the condom. The “dumbbell” section is used for tensile testing thicker rubber articles and its proponents claim more uniform results than the “ring”. On the other difficult to measure with the hand, elongation at break is more “dumbbell”.
FEBRUARY 1881 VOL. 48 NO. 2
181
CONTRACEPTION TABLE
llla
Tensile characteristics of unused condoms and condoms broken in use: Middle versus near-teat sections (all irradiated): Mean and Standard Deviation
(SD)
More recently, Standards and specifications have tended to move toward favouring force at break rather than tensile strength. This is because tensile strength measurement requires measurement of the thickness of the condom wall, which is difficult with heavily textured condoms.
The size of the sample was limited by the availability of used, broken condoms. However, in routine practice, a batch of up to 100,000 condoms may be tensile tested utilizing as few as five condoms (IS02859 double sampling plan for reduced inspection and multiple sampling plans for normal inspection allow 5 and 3 condoms in the first sample). There is no reason to believe that the exduded condoms (with large tears) had significantly different tensile properties. Tears in thin rubber membranes (as opposed to well-formed holes) disseminate very rapidly once they have started. Thus a large tear would seem unlikely to indicate factors that were present before the condom ruptured, and is probably due to physical activity by the wearer after the initial tear.
The slight tendency for broken condoms testing of their distal parts as compared
182
not to score as well on tensile to their mid parts is of interest.
FEBRUARY 1991 VOL. 43 NO. 2
CONTRACEPTION TABLE Tensile
lllb
characteristics of unused condoms and condoms Middle versus near-teat sections (all irradiated):
Broken
broken Range
in use:
condoms
Further (and larger) studies finding. Nevertheless, even more appropriate for testing, sections from failed condoms Standards for tensile testing.
should be considered to investigate this if “near-teat” samples were found to be it is noteworthy that in this study these still all passed the current and proposed
Finally, it is self-evident that a good quality condom needs to be made from rubber with good tensile properties. Unfortunately, this study suggests that tensile testing does not offer any added assurance against a condom breaking in use. We could find no other study that has correlated the performance of condoms on tensile testing with condom failure in vivo. As the inflation test also stresses the condom, it alone may be sufficient to test condom strength.
For Australia it may be that limited resources would be better more systematic policing [4,17] of those condoms available Australian market rather than complicating the Standard.
FEBRUARY
1991 VOL. 43 NO. 2
spent on on the
183
CONTRACEPTION
ACKNOWLEDGMENTS This study is part of the Condom Project, University of Sydney, which was supported by a grant from the Commonwealth AIDS Research We thank Juliet Richters for coordinating the Grants Committee. Condom Project, Ansell International for providing condoms, as well as the staff and patients of the Taylor Square Private Clinic, Sydney STD Centre and the University Health Service at the University of Sydney for their kind co-operation.
REFERENCES 1. 2. 3.
4.
5. 6. 7.
8.
9.
10.
11. 12.
184
Condoms for the prevention of HIV Potts M, Short RV. transmission: cultural dimensions. AIDS 1989; 3: S259-63. Free MJ, Skiens EW, Morrow MM. Relationship between condom strength and failure during use. Contraception 1980; 22: 31-7. Free MJ, Hutchings J, Lubis F, Natakusumah R. An assessment of burst strength distribution data for monitoring quality of condom Contraception 1986; 33: 258-299. stocks in developing countries. Katznelson S, Drew WL, Mintz L. Efficacy of the condom as a barrier to the transmission of cytomegalovirus. J InfectDis 1984; 150: 155-7. Conant MA, Spicer DW, Smith CD. Herpes simplex virus transmission: condom studies. Sex Transm Dis 1984; 11: 94-5. Minuk GY, Bohme CE, Bowen TJ. Condoms and hepatitis B virus infection [letter]. Ann Intern Med 1986; 104: 584. Conant M, Hardy D, Sernatinger J, Spicer D, Levy JA. Condoms prevent transmission of AIDS-associated retrovirus. JAMA 1986; 355: 1706. Van de Perre P, Jacob D, Sprecher-Goldberger S. The latex condom, an efficient barrier against sexual transmission of AIDrelated viruses. AIDS 1987; 1: 49-52. Rietmeijer CAM, Krebs JW, Feorino PM, Judson FN. Condoms as physical and chemical barriers against human immuno-deficiency virus. JAMA 1988; 259: 1851-3. Judson FN, Ehret JM, Bodin GF, Levin MJ, Rietmeijer CAM. In vitro evaluations of condoms with and without nonoxynol as physical and chemical barriers against Chlamydia trachomatis, herpes simplex virus type 2, and human immuno-deficiency virus. Sex Transm Dis 1988; 16: 51-6. Richters J, Donovan B, Gerofi J, Watson L. Low condom breakage rate in commercial sex [letter]. Lancet 1988; 2: 1487-8. Van Griensven GJP, de Vroome EMM, Tielman RAP, Coutinho RA. Failure rate of condoms during anogenital intercourse in homosexual men. Genitourin Med 1988: 64: 344-6.
FEBRUARY 1991 VOL. 43 NO. 2
CONTRACEPTION 13. 14.
15.
16.
17.
Hatcher RA, Hughes MS. The truth about condoms. Siecus Report 1988; 17 (2): 1-9. Tindall B, Swanson C, Donovan B, Cooper DA. Sexual practices and condom usage in a cohort of homosexual men in relation to human immunodeficiency virus status. Med J Aust 1989; 151: 318-22. Lacey S. Honi Soit (University of Beware the condom kit. Sydney) 1989; 23: 17. Reprinted in Healthright 1989; (1): 20-l. Stube R, Voeller B, Davidhazy A. High Speed Cinematography of the initial break-point of latex condoms during the Air-burst Test. Contraception 1990; 6: 591-603. Australian Consumers Association. Condoms revisited. Choice 1989 (Jan): 42-5.
FEBRUARY 1991 VOL. 43 NO. 2
185