Surveillance of H.I.V.
Speech given by Professor Sydney Bell, Medical Director Eastpath at Prince Henry and Prince of Wales Hospitals – Sydney
Conference Paper: AIDS – Have we got it Right?
A conference organised by The Australian Doctors Fund Ltd.
Hosted by Professor Fred Hollows & ADF Chairman Dr. Bruce Shepherd
Sheraton Sydney Airport Hilton
May 14th and 15th, 1992
The differences in the epidemiology of H.I.V. infection in different populations throughout the world makes it imperative that we collect accurate local data. Just before I go into how well we are collecting information on H.I.V. infections in this city I would like to give an example of the difference in epidemiology of the disease in our society to that in other western societies.
This table compares the H.I.V. positivity rate in prisoners in New York city and in N.S.W. Male prisoners in New York have a positivity rate of more than thirty times that of N.S.W. prisoners and female prisoners in New York city are eighty times more likely to be H.I.V. positive than they are in N.S.W. These major differences illustrate why we can’t rely on overseas data alone to base our public health action against this disease. We must get local knowledge.
Now I would like to explore how we have been collecting this information and how well we have been doing it.
This chart shows how information on new diagnoses of H.I.V. is collected. Laboratories are the sole source of notification of this disease and have been for the last seven years. The attending doctor has played almost no part in the notification process and in the new Public Health Act, at present, a medical practitioner does not have any obligation to notify H.I.V. The clinical details of patients where the diagnosis of a new case of H.I.V. infection has been made are collected exclusively by the four reference laboratories in H.I.V. testing. (In fact there are three reference laboratories and another laboratory which does its own confirmatory testing). Each of these laboratories sorts its positive results into new and old cases and records information such as age, sex, exposure category and clinical status before passing this information on to the N.S.W. Health Department. The Health Department accumulates this information and I am told that, up to the present, it is unable and does not attempt to clean up these data any further. The Health Department then passes on the same information to the National Center in H.I.V. Epidemiology and Clinical Research. As far as I am aware all of the information regarding the new diagnoses of H.I.V., including case numbers, is as is determined by the four laboratories. It is not modified in any way by the Health Department and although the National Centre receives some information from other sources, for example, its S.T.D. Clinic surveillance, I think this is separate to the National database – perhaps Dr. Kaldor, could expand on this.
Therefore if the source of N.S.W. data on new diagnoses is these four laboratories it seemed to me it would be worthwhile to look at the quality of the data they receive. It would have a significant effect on the quality of data being circulated on a national basis. I was able to obtain from one of the reference laboratories information on their last years positive results, which approximated 200, and I also examined 200 requests for H.I.V. testing – essentially the quality of the information supplied in the two groups was the same.
Before going on any further I need to tell you how laboratories collect the data. It is by way of a uniform request form for H.I.V. testing and this is what it looks like. It was agreed that the four laboratories would use this form and it is from this form alone that the information is extracted by the laboratory and sent to the Health Department. There is no need to attempt to read the details of the form; as we go along I will extract the appropriate section and enlarge it for you.
As you would expect these forms are completed with varying degrees of thoroughness. I was going to show a blank form but picked up this one in error – it is nearly blank.
Most forms are filled in a little better than this one. It has only the laboratory code, and I have obscured it for privacy sake, and a signature which does not need to be obscured to protect the privacy of its owner.
Also, before examining in detail the data from this laboratory we need to understand how laboratories define a new diagnosis. This slide details this definition, i.e., it is a positive test where the request form does not indicate that a patient had previously tested as positive and there probably should be and an oblique before the or so that it is and/or – – – or there is not a positive result for that patient in the laboratory’s records.
For today’s purposes the first part of the request form which we are interested in is that which indicates previous H.I.V. testing and the results. There are two ways that you can fail to respond to this question: you can either neglect to tick any box or else indicate that the test has been done but failed to give a result. Both of these answers are equally unhelpful.
Thirty-six Percent (36%) of all request forms failed to indicate that the patient had been tested or else the result of a previous testing was not included. Therefore, in 36% of cases reported as new to the State positives it was not known whether a previous positive test was recorded in another laboratory. They weren’t on this particular reference laboratory’s file but it is not indicated that they had tested positive elsewhere.
Going back to the definition – The 36% where there is an inadequate description of previous testing would have to be in this part of the definition, i.e., no previous positive test reported because this is the only source the laboratory has to obtain this information. The second parameter used to define a new diagnosis is where the patient is in the laboratory’s record as a positive result. This can also present problems.
This is the part of the request form which the laboratory uses to determine if the patient is on their records – the patient code or identifier.
To locate the patient in their records the laboratory needs to be supplied with a unique identifier and they get this in just over half the request forms – 53% in fact. The unique identifier is derived from the patients name, and provided that the patient uses the same name at each attendance, this identifier allows a match in the laboratory records. In another 27% of cases a public clinic medical record number was supplied. This is an identifiable number if the patient has always attended and continues to attend that particular clinic but not if the patient attends, or will attend, another clinic or a private practitioner. So it has a limited value in the laboratory in preventing double counting if we consider the state as a whole. Twenty percent (20%) of the forms simply included a laboratory number of a referring laboratory. This number is of no value to the reference laboratory because it changes each time the patient is tested and will be regarded each time as a new patient.
The four laboratories have no access to each others files therefore they have considerable difficulty in defining in many cues what is a new diagnosis and there is considerable scope for inaccuracy in the number reported using the present method.
The next three slides show four other fields for which laboratories attempt to collect information. In this extract of the request form is the space for noting the patients post code and the patient’s sex.
In the next slide is a field where it only requires a box to be marked, indicating the mode of infection. The mode of infection is split up into those which are well known to all of you here.
The third slide defines the clinical status of the patient: again, all that is required is a tick. If the requesting practitioners want to they can add details of other clinical status or add some comment.
This slide analyses the data in each of those fields on the previous slide and shows that the laboratory also had difficulty in obtaining accurate information in each case. Fifty-six percent (56%) of the request forms failed to include the post code of the patient and at the other end, 16% of the forms did not even indicate the patients sex. The mode of infection, which is clearly a most crucial piece of information, was not indicated in 46% of patients. Almost the same number failed to give any indication of the clinical status of the patient. I would like to emphasise again that the request form is the only source of all the information which is collected on H.I.V. infection and if this information is not supplied on the request form it will absent from the accumulated national data.
I accept that with sexually transmitted diseases for one reason or another we have always had problems in collecting accurate data but these are nothing compared with those associated with getting accurate information on the results of H.I.V. testing. This is despite the expenditure of a lot of money over seven years and the restriction of H.I.V. testing to a small number of laboratories. I don’t know if anybody has the answer or how to get surveillance right – I don’t but I have a few constructive criticisms.
In the first place I would argue that we need to simplify the system of collecting data. In the past there has been an idea that we must adopt a high tech approach to the collection of information on H.I.V. As a result there has been a preoccupation with computers – should we be using a mainframe with custom made software or PC’s with C.R.S. or with clipper. When we consider that the annual number of new patients works out at 3-1/2 per lab per week and there are only seven fields to be completed I suggest that we may be better off with less sophisticated methods of number crunching.
It is my view that another mistake we have made is not to involve the attending doctor in the notification process. The failure to make this disease a doctor notifiable one underestimates the concern generally expressed by members of the medical profession and it hasn’t helped in collecting accurate information on this disease.
If strict privacy is a condition of acceptability of the surveillance system then for the system to work this privacy must be observed. However, it is the identity which must be kept secret, not the details of the disease nor the method of acquisition of the infection. We should try to get rid of the mystery which quite frequently cloaks oven the anonymous case.
I am not sure how to persuade more people who are undertaking risk activities to have their H.I.V. status tested. Others who are more expert in this area than I am probably would know how to do this but I have not seen a lot of evidence of activity in this area. For example: I haven’t seen much publicity given to the fact that H.I.V. testing is free, is freely available and performed with the highest standards of accuracy and reproducibility. Just on this point I must emphasise that my criticisms are not aimed at testing itself but rather what is done with the results. In fact the actual performance of H.I.V. testing is one of the few things we’ve got right in the AIDS saga. Perhaps one way of achieving a greater compliance with testing and with the supply of information is if both doctors and the patients were presented with a more accurate picture of the epidemiology of this disease in our own city.
Mr. Chairman – If we can get H.I.V. surveillance right then it follows that planning and predictions we hear so much about will be much more soundly based than they are at present.