Randomised clinical trial investigating the specificity of a novel skin test (C-Tb) for diagnosis of M. tuberculosis infection

Background

Tuberculin skin testing is simple and relatively inexpensive, but the specificity of PPD is affected by BCG vaccination.

Objective

Determine optimal dose and specificity of recombinant ESAT-6 and CFP-10 (C-Tb) produced in Lactococcus lactis for diagnosis of M. tuberculosis infection.

Methods

In a dose finding phase I trial 0.01 or 0.1 µg preserved and unpreserved C-Tb was injected by Mantoux technique in 38 patients with active tuberculosis and induration responses measured. In a phase II specificity trial in 151 uninfected, BCG vaccinated participants 0.1 µg C-Tb was compared to 2 TU PPD.

Results

0.1 µg C-Tb gave a median induration of 15 mm after 2 days. Phenol preservation did not affect the response. The specificity of C-Tb was 99.3% (95% CI 96–100%) regarding indurations ≥5 mm as a positive outcome. This was higher than the specificity of PPD (63% using a cut-off of 5 mm or 92% using a cut-off of 15 mm to adjust for non-specific BCG responses). Local adverse reactions following C-Tb injection included transient itching and discomfort as expected components of the immune response.

Conclusion

C-Tb offers a simple and convenient skin test to diagnose M. tuberculosis infection using a single, universal cut-off unaffected by BCG vaccination.

Trial Registration

ClinicalTrials.gov NCT01033929 and NCT01241188.

Successful treatment of ulcerous skin lesion caused by mistaken intradermal injection of BCG (Bacille de Calmette et Guerin) vaccine with anti-tuberculous drugs and systemic administration of corticosteroid

"Tokyo 172" BCG vaccine designed for percutaneous inoculation is widely used in Japan. This vaccine is a much higher concentration of M. bovis BCG than that of the BCG vaccine designed for intradermal inoculation widely used in other countries. A patient who suffered from an ulcerous skin lesion as a result of the intradermal injection of "Tokyo 172" BCG vaccine accidentally was referred to our hospital. Systemic corticosteroid was administered with anti-tuberculous drugs, achieving a complete improvement of the skin lesion.

Foreign body reaction involving a Mantoux test site

A 41-year-old woman presented with a history of a solitary pustular erythematous lesion occurring at the site of a Mantoux test performed 10 months previously. The histopathology examination revealed a suppurative and foreign body giant cell reaction to numerous keratin flakes. Culture of the tissue was negative for both aerobic and anaerobic organisms including mycobacteria. We postulate that the reaction in our patient may have been secondary to the implantation of epidermal keratin or the entrapment of hair into the dermis during the intradermal injection of tuberculin purified protein derivative.

Skin test performed with highly purified Mycobacterium tuberculosis recombinant protein triggers tuberculin shock in infected guinea pigs

Tuberculin shock due to inoculation of Mycobacterium tuberculosis antigens in patients with tuberculosis is a serious syndrome originally described over 100 years ago by Robert Koch. Here, we present experimental evidence that a single M. tuberculosis recombinant protein, CFP-10, triggers this syndrome. Intradermal inoculation of CFP-10 elicits in M. tuberculosis-infected mice high levels of serum tumor necrosis factor alpha and causes tuberculin shock in infected guinea pigs characterized by hypothermia and death within 6 to 48 h after the antigen inoculation. Autopsies of these animals revealed intense polycythemia and hemorrhagic patches in the lung parenchyma, a pathological observation consistent with tuberculin shock. These results point to the possible occurrence of tuberculin shock in sensitive individuals inoculated with highly purified M. tuberculosis recombinant proteins as vaccine candidates or skin test reagents.

A study of the association between delayed type hypersensitivity reaction to mycobacterium tuberculosis and atopy in asthmatic children

The purpose of this study was to investigate if there is an inverse association between Mycobacterium tuberculosis infection and atopy among children living in rural and semi urban areas in El Behira governorate, Egypt.

METHODS

All the studied children were BCG vaccinated in their newborn period. In Tuberculin testing, indurations greater than or equal to 5 mm were accepted as positive. For atopy, the most common aeroallergens were used in skin intradermal testing, and reactions > or = 3 mm were accepted as positive.

RESULTS

Among 150 studied children whose ages ranged from 4-8 years, 89 patients were purified protein derivative (PPD) negative whereas in 61 patients PPD was positive. Among the PPD negative patients skin intradermal test was positive for atopy in 51.6% (n = 46), while among the PPD positive patients skin intradermal test was positive in 52.4% (n = 32). As the two groups were compared for having positive intradermal skin test reaction, no statistically significant difference was detected between them (p >0.05).

CONCLUSIONS

In this study no statistically significant difference was detected between Mycobacterium tuberculosis infection as indicated by positive PPD positivity and atopy tested by skin intradermal injection of common aeroallergens.

[Remarkable restricted tuberculosis epidemics in 2001/2002 in two Bavarian regions]

Even if the incidence is further decreasing, tuberculosis must not be underestimated in Germany. In 2001, the public health service revealed four noteworthy molecular-biologically substantiated tuberculosis infection chains in Upper Bavaria and Upper Palatinate. An alcohol-addict frequenting the table reserved for regulars in an inn located in the district of E. was the origin for a small epidemic with seven tuberculosis cases, whereof six were contagious. In the district of D., a manager causes two illnesses at the workplace, and one tuberculosis case as well as two tuberculin conversions after visiting a skiing hut. An external cleaning lady, who had not been examined previously, causes tuberculosis in a three-year old girl in a rehabilitation clinic in the Upper Bavarian district of BT. The cavernous pulmonary tuberculosis, which was not examined for a long period of time in a nursery-school teacher, caused tuberculosis in a three-year-old girl and tuberculin conversion in thirty-four children in the Upper Palatinate region.

[Reduction of excessive reactions after tuberculin skin test (mendel-mantoux method)]

In 2.5 % of cases excessive reaction with formation of blisters and local necrosis is seen after tuberculin skin testing with Mendel-Mantoux technique. The objective of this prospective study was to determine whether this rate can be reduced by pretesting. 426 contacts of cases with contagious pulmonary tuberculosis were examined in a public health office. A tuberculin skin test in Mendel-Mantoux technique with 1 unit purified tuberculin Behring (GT 1, bioequivalent to 0.5 units PPD-S) was applied and the results read after 3 to 7 days. Negative results were retested with 10 units (GT 10, bioequivalent to 5 units PPD-S). 422 patients completed the examination course as planned. In two cases forming of blisters was noticed. The difference between this observed rate of 0.5 % and the published rate of 2.5 % is highly significant. The alternative hypothesis that pretesting reduces the rate of excessive reactions can be assumed.

[Methods for the control of quality in mass tuberculin tests]

It is possible to achieve a qualitative annual intradermal testing of children and adolescents by the Mantoux test with 2 TE PPD-L and to form Dispensary Registration Group 6 completely only when there is a combination of a mass tuberculin diagnosis, team's well organized work and systematic control methods for its work quality. Standards have been developed for the quality of registration of Group 6 patients and for that of registration of positive Mantoux tests with 2 TE PPD-L, for the completeness of formation of the above group of patients, for organization of controlled chemoprophylaxis in children's collective bodies.

Immediate hypersensitivity reactions after use of tuberculin skin testing

This report describes the frequency and characteristics of serious or life-threatening hypersensitivity reactions to the tuberculin skin test over an 11-year period through November 2000. There were 24 reports and no deaths, indicating that such reactions are rare (0.08 reported reactions per million doses of tuberculin).

Tuberculin test

Although tuberculin test is widely used for detection of tuberculous infection among children, there is no clear understanding about its performance and interpretation. This article has been written with the purpose of elucidating the performance and interpretation of standard tuberculin test, based on the experiences gained at the National Tuberculosis Institute, Bangalore and other centres. The standard tuberculin test involves intradermal injection of '1TU PPD RT23 with Tween 80' on the mid-volar aspect of forearm and measurement of the maximum transverse diameter of induration after 3 days. Larger the size of induration, higher is the probability of it being due to tuberculous infection. The majority of reactions with induration size of 15 mm and above are attributable to infection with tubercle bacilli, irrespective of BCG-vaccination status. While indurations of less than 5 mm indicate absence of any kind of tuberculin sensitivity, the majority of indurations in 5-9 mm range are usually of non-tuberculous nature. An induration of 10-14 mm requires more careful interpretation. It is more likely to be attributable to infection with tubercle bacilli in case of history of contact with smear positive case or among children with clinical findings of tuberculosis. However, the size of induration in an infected child may be diminished in the presence of immuno-suppressive conditions. One should also consider the purpose of the test while interpreting the test results.

Correlation between CD4+ lymphocyte counts, concurrent antigen skin test and tuberculin skin test reactivity in human immunodeficiency virus type 1-infected and -uninfected children with tuberculosis

BACKGROUND

HIV-infected children are at high risk of developing tuberculosis after infection by Mycobacterium tuberculosis. Emphasis is placed on tuberculin skin testing (TST) for diagnosing tuberculosis in children; however, its value in HIV-infected children is controversial.

OBJECTIVES

To determine whether concurrent antigen testing and/or CD4+ lymphocyte counts help in the interpretation of the TST in children with tuberculosis.

METHODS

Children eligible for the study were diagnosed as having tuberculosis on clinical criteria. CD4+ lymphocyte counts and delayed-type hypersensitivity (DTH) test, using the CMI Multitest were performed when tuberculosis was diagnosed.

RESULTS

One hundred thirty children were enrolled. Tuberculin reactivity was lower in HIV-infected children at all cutoff levels than in HIV-uninfected children (P < 0.0001). The positive predictive value of normal CD4+ lymphocyte counts in predicting tuberculin reactions of > or =5 mm (in HIV-1-infected) and > or =10 mm (in HIV-uninfected patients) were 50 and 80.3%, respectively (P < 0.0001). An intact DTH reaction to the CMI Multitest in predicting reactions of > or =5 mm and > or =10 mm to tuberculin in HIV-infected and -uninfected children were 55 and 76%, respectively (P < 0.001). Kwashiorkor was responsible for 53.3% of false-negative TST in HIV-uninfected children with normal CD4+ lymphocyte counts.

CONCLUSION

TST is of limited value as an adjunct in diagnosing tuberculosis in HIV-infected children. CD4+ lymphocyte counts and concurrent DTH testing are not useful for predicting tuberculin reactivity in HIV-infected patients with tuberculosis.

Severe irreversible optic neuritis following Mantoux tuberculin skin test in a child with multiple sclerosis--a case report

A 12-year-old girl was diagnosed as suffering from multiple sclerosis. At age 14, just after recovery from an exacerbation of MS with left-sided optic neuritis, she underwent a Mantoux tuberculin skin test. Within 30 minutes she developed complete irreversible optic neuropathy of the left eye. This case illustrates the urge for caution to perform vaccinations and tuberculin skin tests not only during progressive disease activity of MS, but also in the reconvalescent phase after an acute exacerbation.

BCG vaccination to prevent tuberculosis in health care workers: a decision analysis

OBJECTIVE

To perform a decision analysis to determine the optimal strategy to prevent tuberculosis (TB) in health care workers with negative tuberculin skin tests.

METHODS

We used a Markov model to study the occurrence of events each year and compared BCG vaccination to annual tuberculin testing plus isoniazid (INH) preventive therapy for those who become skin test positive. The outcome measures studied were the number of cases and deaths from TB and BCG and/or INH adverse reactions over 10 years.

RESULTS

Annual tuberculin testing decreases the number of TB cases by 9% and BCG vaccination decreases the number by 49%, relative to no prevention intervention. BCG vaccination results in fewer deaths than annual tuberculin testing if the workplace incidence of Mycobacterium tuberculosis infection is greater than 0.06%, BCG vaccination effectiveness exceeds 3%, or the rate of fatal BCG adverse reactions is less than 15 times the rate reported in the literature.

CONCLUSIONS

BCG vaccination results in less morbidity and mortality than annual tuberculin skin testing for health care workers in workplaces with documented TB transmission despite comprehensive infection control policies and procedures. Current policy on the prevention of TB among health care workers should be reconsidered.

Cellulitis versus positive purified protein derivative? A case report and review of the literature

The tuberculin skin test is one of the most widely used diagnostic aids ever developed and remains the only technique of detecting Mycobacterium tuberculosis infection other than actually culturing the organism. False-positives are an acknowledged problem, especially among health care workers (HCW), in whom rescreening can raise more questions than answers. A HCW presented with a severe response to an annual screening test and was retested 6 weeks later with normal results (non-reactive). Causes of false-positives (not including cross-reactivity) are discussed. Readers of the purified protein derivative reaction need to consider alternative explanations for a significant response than infection with tuberculosis, given the medical history and nature of response.

Sweet-like syndrome in a patient with acute myeloid leukaemia

A 45-year-old Malay lady developed brisk vesicular, plaque-like reaction to a Mantoux test concomitant with a diagnosis of acute myeloid leukaemia (AML). The lesion resolved one month after chemotherapy. Similar lesions developed later after she was bitten by mosquitoes on the forearms. She also had the lesions over her cheek. A skin biopsy showed infiltration of the dermis with neutrophils and some monocytoid cells. The lesion resolved one week after prednisolone therapy.

Influence of needle gauge in Mantoux skin testing

STUDY OBJECTIVE

To determine the influence of needle gauge in Mantoux skin testing for tuberculosis.

DESIGN

Randomized selection of either a 27- or 30-gauge 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 27-gauge needles caused increased bleeding and bruising compared with 30-gauge needles (p < or = 0.007 for each). However, the 27-gauge needle produced larger blebs and less leakage of tuberculin solution (p < or = 0.0003).

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.

Tuberculin skin-test-induced uveitis in the absence of tuberculosis

A 16-year-old Caucasian girl who showed no evidence of tuberculosis or other systemic disease developed acute panuveitis progressing to bilateral serous retinal detachments following purified protein derivative (PPD) skin testing on two separate occasions separated by an interval of 8 years. Both episodes responded rapidly to steroid therapy. Uveal hypersensitivity to PPD skin testing has been described in the presence of ocular or systemic tuberculosis, Eales' disease, and the Vogt-Koyanagi-Harada syndrome (VKH). Our case, however, suggests that profound uveitis may be precipitated by routine PPD skin testing alone.

Lymphangitis after tuberculin test

After Mantoux testing with purified protein derivative (PPD) equivalent to 5 tuberculin units (TU), a 28 yr old man developed extensive erythema, induration and proximal lymphangitis. This is the only such case observed after Mantoux testing in approximately 500,000 subjects during 10 yrs in the Greek Army.

[Tuberculin allergy in BCG-vaccinated children (author's transl)]

Frequency, duration and intensity of tuberculin allergy was tested in 431 children, vaccinated as neonates, and compared with the data of 400 non-vaccinated children, and 30 children with tuberculosis. When tested with 100 TE, 59% of the vaccinees showed a positive reaction at the age of 5 years, still 36% reacted positively in the 7th year. 4,7% of the non-vaccinated children were tuberculin-positive in 7--9 years old. Near half of the children reacting positively to tuberculin without suffering from tuberculosis reacted to 100 TE, nearly all tuberculous children already reacted positively to a lower dose. The overall rate of protection against tuberculosis was more than 90% in the first 5 years of life. Miliar-Tb. or Tb-meningitis was not seen in vaccinees, but 4 times in non protected children. General BCG-vaccination in newborns is recommended.