A novel approach to the assessment of variations in the human platelet count.

This is the first report of a method to assess the significance of numerical changes in the platelet count based upon a result exceeding the normal intra-individual variation in platelet numbers. Serial platelet counts from 3,789 subjects were analysed to determine the intra-individual variation in platelet numbers. A platelet count difference of 98 x 10(9)/L in males was found to represent a change that would occur by chance in less than 1 in 1,000 platelet count determinations. Tables to determine the significance of platelet number variations, given N previous observations, are provided at two probability levels. The repeatability of the platelet count was calculated as 0.871 (males) and 0.849 (females) indicating that the heritability of platelet count is high and that the platelet count is predominantly genetically determined. A seasonal variation in platelet count was found with a 'winter' versus 'summer' difference of 5.10 X 10(9)/L (males) and 5.82 x 10(9)/L (females).

Suitability of casemix classification for output funding of blood services in Victoria. Victorian Blood Users Group.

OBJECTIVE: To study the suitability of diagnosis-related groups (DRGs) to quantify blood use in order to fund hospitals directly for fresh blood components. DESIGN: (i) Retrospective empirical analysis of hospital inpatient separation data, matching DRG classification with blood usage. (ii) Prediction of blood usage based on actual DRGs and comparison with actual blood products issued from the blood service. SETTING: Eight large public hospitals, April 1994-March 1995, the Department of Human Services and the Australian Red Cross Blood Service in Victoria, 1994-1997. MAIN OUTCOME MEASURES: Requirement for transfusion according to DRG; quantity of blood or blood products transfused; and statistical reliability of measuring blood component usage by DRG. RESULTS: A match between patient records and transfusion records for 287,117 patient separations showed that the patients had received 51,115 units of red cells, 30,451 units of platelet concentrates, 9043 units of fresh frozen plasma and 1273 units of cryoprecipitate. Ten per cent of DRGs (527) accounted for over 70% of blood product usage. The numbers of DRGs in which blood products were used for at least 30 separations (with a relative SEM [for units of blood used per separations using blood] of up to 20% at a 95% confidence level) were 56 for red cells, 8 for platelets and 4 for fresh frozen plasma. Estimates of red cell usage calculated from actual DRGs for three consecutive years (1994-1997) showed that DRGs predicted aggregate issues of red cells by the Red Cross Blood Service (ratio of actual red cells issued to red cell usage estimates were 1.036 for 1994-95, 0.994 for 1995-96, and 1.021 for 1996-97, respectively). CONCLUSION: DRGs are moderately good predictors of blood product usage, and could be used to allocate funds for blood products to hospitals instead of to the blood service. However, DRG data are not designed to manage blood issue policies, because DRGs do not represent single diagnoses or procedures and some are surrogate descriptions of procedures.

The risk of transmitting HCV, HBV or HIV by blood transfusion in Victoria.

OBJECTIVE: To report the incidence rate of hepatitis B virus (HBV), hepatitis C virus (HCV) and HIV in Victorian repeat blood donors and to derive the residual risk of transmission of the viruses by screened blood transfusion. DESIGN: The interval from the previous whole blood donation was extracted retrospectively from Victorian Red Cross Blood Bank records for each of the 358332 repeat donations given between March 1994 and December 1995. Records of repeat donors found positive for the viruses in this period were traced to the previous seronegative donation and accepted if screened by the same test. For each virus, the number of previous donations screened by the same test was calculated and the sum of all donation intervals used to derive the incidence of infection in the repeat donor population. Published intervals after infection (when a donation can be infective although seronegative) were used to calculate the risk of release of a seronegative unit which would be infective. PARTICIPANTS AND SETTING: Homologous blood donors at the Red Cross Blood Bank of Victoria. MAIN OUTCOME MEASURES: Incidence rate of HBV, HCV and HIV in regular blood donors and risk of infective donations being seronegative. RESULTS: The incidence of infection in repeat donors was: HBV: 1.67 per 100000 person-years; HCV: 1.89 per 100000 person-years; and HIV: 1.31 per 100000 person-years. The risk of a seronegative repeat donation being infective was: HBV: 2.71 per million donations (adjusted to 6.45 to account for viraemias which remain seronegative); HCV: 4.27 per million donations; and HIV: 0.79 per million donations. CONCLUSION: The risk of transmitting HCV, HBV or HIV by repeat blood donors is low and compares favourably with overseas data. Repeat donors have an incidence rate of HIV and HBV comparable to that of the general population, but the incidence rate of HCV is lower for repeat donors than in the general population.

Is screening of Australian blood donors for HTLV-I necessary?

OBJECTIVE: To re-examine the 1992 decision by Australian Red Cross for its blood banks to screen blood donors for antibody to human T-cell lymphotropic virus type I (HTLV-I) by determining the risk of its transmission by blood transfusion. METHODS: Data on patterns of return behaviour by repeat blood donors in Victoria were modelled to deduce the number of donors giving repeat donations in Australia from March 1993 to December 1995. Data on annual donor and issued cellular blood products from 1992 to 1995 were obtained from national Red Cross statistics. From the numbers of donations given by repeat donors, together with the number of new donors, the number tested for HTLV-I was deduced. The number and characteristics of donors screened positive for HTLV-I antibody were collated. The crude prevalence of HTLV-I was calculated by dividing the number of donors with HTLV-I by the total number of donors (repeat donors and new donors). The incidence of HTLV-I was calculated by dividing the number of seroconversions in repeat donors by the cumulative period of donor exposure. RESULTS: Sixteen homologous and five autologous donors were found to be positive for HTLV-I; none seroconverted and no clear risk factors for HTLV-I were identified. The prevalence of HTLV-I in Australian donors is 1 in 100,000 and the incidence less than 1 in 1 million person-years. In the absence of HTLV-I screening, the calculated risk of a transfused patient developing HTLV-I infection is 1 in 370,000, with a risk of developing HTLV-I disease of 1 in 9 to 15 million. CONCLUSION: Three possible future courses of action for screening for HTLV-I are to screen every donation, to screen only new donors or to discontinue screening altogether. Using the information in this study, public discussion should be encouraged to assist stakeholders to agree on an acceptable level of risk and an appropriate level of screening for HTLV-I in Australia.

Some characteristics of blood shed into the Solcotrans postoperative orthopaedic drainage/reinfusion system.

OBJECTIVE: To assess the suitability of blood shed into the Solcotrans orthopaedic autotransfusion system as a source of autologous blood for transfusion. DESIGN: Blood samples were taken from patients after surgery and from shed blood within the Solcotrans units. SETTING: Surgery was performed at a public hospital. PATIENTS: All six patients underwent total knee replacements. MAIN OUTCOME MEASURES: Measurements were made of haemoglobin, haematocrit, platelets, pH, potassium, plasma haemoglobin, fibrinogen, D-dimer, plasminogen activator, thromboplastin and fibrinopeptide A. The non-activated partial thromboplastin time was estimated. Shed blood was compared with homologous whole blood to assess the thrombogenic potential of shed blood in vitro. RESULTS: The haemoglobin and haematocrit levels of the shed blood were significantly lower than venous blood (P = 0.008). Levels of potassium in shed blood were normal although there was significant haemolysis. Shed blood was depleted of clotting factors, with increased levels of D-dimer (16-128 g/L). Activation of the coagulation pathway within the shed blood was shown by a shortened non-activated partial thromboplastin time (90-120 s), and detectable levels of thromboplastin. Propionibacterium acnes was isolated from one of the units. CONCLUSION: Reinfusion of large volumes of shed blood should probably be avoided, but use of the Solcotrans orthopaedic transfusion system in conjunction with other autologous transfusion practices can reduce the patient's requirement for homologous blood.

The transfused population of Canterbury, New Zealand, and its mortality.

All 367 recipients and 1,385 donations transfused over a 40-day period were traced and compared by sex, age and discharge diagnosis with the 5,955 concurrent discharges from all general and obstetric hospitals in the area. 6% of discharged patients had been transfused. 21% of transfused patients were dead within 1 year, and at least 30% will die within 5 years. 228 donations of platelet concentrates were required for 7 recipients, 6 of whom died within 2 years. The mortality of blood recipients is overestimated if tracked from donors of multiple components.