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Reply to ‘Problems in medical injection study’

Priddy, Francesa; Tesfaye, Fikrub; Mengistu, Yohannesb; Rothenberg, Richarda; Fitzmaurice, Dorothya; Mariam, Damen Haileb; del Rio, Carlosa; Oli, Kebedeb; Worku, Alemayehub

doi: 10.1097/01.aids.0000199016.73762.4c

aEmory University School of Medicine, Decatur, GA 30317, USA

bAddis Ababa University Faculty of Medicine, Addis Ababa, Ethiopia.

Received 18 April, 2005

Accepted 20 April, 2005

Mr Hogan is correct that our sample is admittedly small and our protocol for HIV RNA in needle flushes was not sensitive for patients with HIV viral loads less than 40 000 copies/ml (4.6 log10). Despite these shortcomings, it is not premature to suggest that medical injection practices of the types we studied are not significant modes of HIV transmission in this region of Ethiopia. Two major findings of our study suggest the limited potential for the medical transmission of HIV through unsafe injections at health facilities. First, we found high rates of patient-purchased disposable needles/syringes used for medical injections. Second, we did not detect HIV RNA in any of 212 used needle flushes (exact 95% confidence interval 0–0.014).

Almost half of all observed injections were administered with a new patient-purchased disposable needle/syringe. The use of new, patient-purchased disposable needles/syringes appeared to be much higher in comparison with a similar injection safety study conducted by our colleagues in 2000 (Y. Berhane, J. Millogo, 2000, unpublished paper). Both patients and providers told us that government sponsored radio announcements over the past year had described the risk of injection-related infection and encouraged patients to purchase their own needles/syringes. It is possible that under observation, medical providers may have been more likely to require patients to purchase a disposable needle/syringe and return to the clinic for their injection. However, because the large majority of therapeutic injections are given as multiday treatments, our observers reported that most patients using new disposable syringes for therapeutic injections had already brought them to the visit.

In situations in which a new disposable syringe was not available, observation bias (the Hawthorne effect) may very well have affected injection practices, and led to our finding of no direct needle re-use. However, despite this bias, we still found over 10% of all observed injections, both therapeutic and vaccination, given with a used, disposable needle/syringe, which had been prepared for re-use. Like Mr Hogan, we found this rate concerning. However, the inability to detect HIV RNA in these needles suggests that despite the concerning rates of re-use of needles that had been prepared for re-use, this mode does not contribute significantly to HIV transmission in this region. Of note is the fact that in the needle collection portion of the study, visits to collect needles were conducted unannounced, and involved collecting all needles that had been used for medical injections and then prepared for re-use, usually the evening before. Therefore, observation bias did not affect our finding of no detectable HIV RNA in used needle flushes.

Studies of recently and chronically HIV-infected, primarily asymptomatic Ethiopian patients found mean HIV viral loads of 4.1–4.6 log10 copies/ml [1,2]. Therefore, even with the relatively low sensitivity of our HIV-RNA testing protocol (unable to detect HIV RNA from patients with viral loads < 4.6 log10 copies/ml), in a region with moderate HIV prevalence and little or no access to antiretroviral therapy, we would expect the majority of HIV-infected patients with a clinical illness requiring therapeutic injection to have HIV viral loads above the lower limit of detection of our protocol.

Therefore, if medical injection practices of this type were a significant route of transmission, we would expect to detect HIV RNA on some used needles. Data from a similar unpublished study of medical injection practices in Cameroon used the same needle flushing protocol on over 1500 intravenous and intramuscular injection needles, directly after use, and found detectable HIV RNA only in needles used for intravenous injection [3]. The most likely explanation for our inability to detect HIV RNA was that the methods to prepare the syringes for re-use such as boiling or the improper use of a steam sterilizer, although imperfect, were sufficient to reduce HIV viral contamination below the level of 40 copies/μl blood, which can be retained in a needle [4].

It is true that the HIV prevalence of needle source patients is unknown, and that our rough HIV prevalence estimate was taken in patients from health centres only. However, used needles were collected in both health stations and health centres and were analysed for HIV RNA, so even if health station populations had a lower HIV prevalence, we would still expect to detect HIV RNA on some used needles.

The arguments for and against medical transmission as a significant route of HIV transmission are based primarily on epidemiological data. Our study is the first published study that we are aware of that actually tested for HIV RNA on medical injection equipment in the field using a fairly sensitive protocol. The high rates of patient-purchased disposable needle use and the lack of HIV viral material in needle flushes suggests that, at least for intramuscular therapeutic injection at health facilities in this region of Ethiopia, medical injection practices do not contribute significantly to HIV transmission.

We do agree that further study is indicated, particularly of medical injection practices in higher prevalence areas, of traditional medical injection practices, and of EPI equipment. In addition, the potential for the transmission of other more infectious agents, such as hepatitis B and C through medical injection practices, could be investigated using this protocol. However, given the reality of conditions in the field and the difficulty of preserving viral material, it will be difficult ever to conduct the perfect study on this subject. Instead of slamming on the brakes, our small study emphasizes the importance of improving accessibility and public awareness of disposable injection equipment, and should renew efforts to improve sharps disposal safety at health facilities in countries such as Ethiopia.

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